//! Adopting a Claude Code session that already exists on a machine.
//!
//! Claude Code keeps every session as JSONL under
//! `~/.claude/projects/<encoded-cwd>/<session-id>.jsonl`, and the CLI can
//! be told to continue one with `--resume <id>`. This module is the two
//! halves of putting that behind the phone: asking a machine what it has,
//! and turning one of those files into the transcript a phone reads.
//!
//! **Continuing is not this module's job.** `claude.rs` already resumes
//! whenever a session directory holds a resume token, for crash recovery,
//! so an import is that same path with the token written up front. There
//! is deliberately no second way to start a session.
//!
//! **The phone never names a file.** It picks an id out of what this
//! module enumerated, and the path is looked up again on the server -- the
//! same rule the setups model follows for providers, and for the same
//! reason: an enrolled token must not be able to turn into "read me this
//! arbitrary path".

use std::collections::HashMap;

use anyhow::{Context, Result};
use serde::Serialize;
use serde_json::Value;

use super::driver::{self, Event};
use super::transport::{Launch, Transport};

/// How much of a transcript's tail is replayed into the phone's view.
///
/// The imported conversation is for reading; *continuing* it is the CLI's
/// job through `--resume`, and it reads the whole file itself regardless
/// of what is shown here. So this is a display budget, not a fidelity one
/// -- and it needs to be a budget, because these files reach tens of
/// megabytes (the session this feature was written in was 39 MB) and every
/// line of it would otherwise cross a WireGuard link to a phone.
const REPLAY_LINES: usize = 2000;

/// Whether a session is open in a CLI somewhere.
///
/// Three answers, because "nobody could check" is not "nobody is using
/// it". Collapsing them would put the dangerous case behind the safe
/// word, which is how the expensive version of this happens: an import
/// that looks permitted, of a session that is being written to.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
#[serde(rename_all = "camelCase")]
pub enum InUse {
    /// Checked, and nothing is running it.
    No,
    /// Checked, and a live CLI has it open.
    Yes,
    /// The machine does not keep the record this is read from, so there is
    /// no answer to be had -- not an answer of "no".
    Unknown,
}

/// One Claude Code session found on a machine.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct Importable {
    /// The CLI's own session id, which is both the file name and the
    /// `--resume` token.
    pub id: String,
    /// Where that session was working, offered as the imported session's
    /// cwd so it resumes pointing at the same tree.
    pub cwd: String,
    /// The first thing a person said in it, for recognising it in a list.
    pub title: String,
    /// Epoch seconds, for ordering by "what I was last doing".
    pub modified: f64,
    pub lines: usize,
    /// How many tokens the model was holding at the last turn.
    ///
    /// The input side of the most recent assistant message's usage --
    /// prompt plus both cache figures -- which is the closest thing to
    /// "what continuing this costs", and unlike the size it is a number
    /// the CLI itself recorded rather than one inferred from the file.
    ///
    /// Size and this disagree in the direction that matters. Most of a big
    /// transcript is usually history from before a compaction, which the
    /// model is no longer given: of the 133 MB session behind the
    /// 2026-08-29 incident, 99% of the bytes sat before its last
    /// compaction summary. A 77 MB file whose context is 10k tokens is
    /// cheap to continue; a smaller one that has never compacted may not
    /// be.
    ///
    /// `None` when no assistant turn has recorded usage yet -- which is
    /// not zero, and is why this is an option rather than a default.
    pub context_tokens: Option<u64>,
    /// Size of the file, in bytes.
    ///
    /// Reported because it is the only thing on a row that predicts what
    /// continuing the session will cost, and lines do not: these
    /// transcripts embed screenshots as base64, so one line can be a
    /// megabyte. The session behind the 2026-08-29 incident was 65 MB
    /// across 13,000 lines, which is a line count that looks unremarkable.
    ///
    /// Shown rather than warned about. Importing a large session is a
    /// choice somebody is entitled to make, and marking it would be the
    /// interface nagging about a decision already taken -- but they should
    /// be able to see what they are taking on.
    pub bytes: u64,
    /// Whether [`title`](Self::title) is a name somebody chose rather than
    /// something read out of the conversation. Sorted on, and worth the
    /// reader knowing: a name is a claim about what a session *is*, and a
    /// last message is only the last thing that happened in it.
    pub named: bool,
    /// Whether a CLI is running this session right now.
    ///
    /// The load-bearing field on this struct. Importing a session that is
    /// already open puts a second `--resume` on one file: the whole
    /// conversation gets duplicated into it, both copies then read each
    /// other's writes as work done elsewhere, and the adopted one is
    /// billed for re-reading everything -- measured on 2026-08-29 at 65 MB
    /// and 154 screenshots, from importing the session the importing agent
    /// was itself running in.
    pub in_use: InUse,
    /// Where it lives. Not serialized: the phone chooses by id and the
    /// server resolves the path, so a path never crosses the wire in
    /// either direction.
    #[serde(skip)]
    pub path: String,
}

/// Asks `transport`'s machine which Claude Code sessions it has.
///
/// One command rather than one per file, for the reason `setups::discover`
/// gives: over ssh each would be its own connection and handshake.
///
/// `stat -c` is GNU-specific, which is fine for the machines here and is
/// the thing to change first if this ever meets a BSD.
pub async fn list(transport: &Transport) -> Result<Vec<Importable>> {
    // Which sessions are open right now, before the files themselves.
    //
    // Claude Code writes a descriptor per live session at
    // `~/.claude/sessions/<pid>.json`, and the pid is the file name. It
    // also records `procStart` -- the kernel's start time for that pid --
    // for the same reason `session::process` does: a pid on its own is
    // reused, so a descriptor left behind by a CLI that crashed would
    // otherwise mark a session as open for as long as something else held
    // its number. Checking both is what makes this a measurement.
    //
    // The `LIVEKNOWN` line says the directory was there to be read at
    // all. Without it an old CLI that keeps no descriptors would look
    // exactly like a machine with nothing running, which is the one
    // mistake this check exists to prevent.
    //
    // Then two questions per file, both answered from the end of it.
    //
    // A rename, if there was one: `/rename` appends a `custom-title`
    // record, and a name somebody chose beats anything inferred from the
    // conversation. Grepped over the whole file rather than its tail,
    // because a session can be named early and talked in for hours after.
    //
    // Then the last several things a person said. The *last*, not the
    // first: the question a list like this answers is "which one was I
    // just in", and every session's opening line is the least distinctive
    // thing about it. Several, because the final ones are often the CLI's
    // own -- a slash command, the caveat wrapped around its output -- and
    // one of those identifies nothing.
    //
    // Tool results are excluded rather than typed messages included, and
    // the difference matters: a tool result is *also* a user record --
    // it is how the API models one -- so grepping the type alone gave a
    // session that ended mid-tool a tail of empty records and a row
    // saying nothing was said, when plenty was. But matching only a
    // string `content` was worse: a message carrying an attachment stores
    // its text in a list, so that reading lost twenty rows rather than
    // two. Excluding `tool_use_id` keeps both shapes of a real message
    // and drops the one that is not.
    let script = listing_script(r#""$HOME"/.claude/projects/*/*.jsonl"#);
    let launch = Launch::new("sh", vec!["-c".to_string(), script], None);
    parse_listing(&transport.capture(&launch).await?)
}

/// The same listing, for one session named by id.
///
/// Importing needs everything a row holds -- the path to follow, how many
/// lines have already been written, what it is called, where it was working
/// and whether something else has it open -- and used to get them by
/// listing *every* session and searching the result. That is a full read of
/// every transcript on the machine, seconds of it, to answer a question
/// about one file; a batch of imports paid it once each. Same script, same
/// parsing, one glob narrower.
pub async fn find(transport: &Transport, id: &str) -> Result<Option<Importable>> {
    if !is_session_id(id) {
        return Ok(None);
    }
    let script = listing_script(r#""$HOME"/.claude/projects/*/"$1".jsonl"#);
    let launch = Launch::new(
        "sh",
        vec!["-c".to_string(), script, "sh".to_string(), id.to_string()],
        None,
    );
    Ok(parse_listing(&transport.capture(&launch).await?)?
        .into_iter()
        .find(|candidate| candidate.id == id))
}

/// What the machine is asked, over whichever set of files `glob` names.
///
/// One script with the glob substituted rather than two that drift: the
/// per-file half decides what a row *is*, and a row has to mean the same
/// thing whether it arrived from a listing or from a lookup. The glob is
/// this module's own text; the only thing that ever crosses from outside is
/// the id, which stays an argument (`$1`) and is checked by
/// [`is_session_id`] first.
fn listing_script(glob: &str) -> String {
    // `replace` rather than `format!`: this is shell, so it is full of
    // braces -- `${s##*/}`, an awk program, the `{[^}]*` that finds a usage
    // record -- and every one of them would have to be doubled to survive a
    // format string. Doubling braces inside a script is exactly the kind of
    // edit that looks right and changes what the shell runs.
    SCRIPT.replace("{glob}", glob)
}

const SCRIPT: &str = r#"
if [ -d "$HOME/.claude/sessions" ]; then
  printf 'LIVEKNOWN\n'
  for s in "$HOME"/.claude/sessions/*.json; do
    [ -f "$s" ] || continue
    pid=${s##*/}; pid=${pid%.json}
    [ -d "/proc/$pid" ] || continue
    start=$(awk '{ n=index($0,") "); $0=substr($0,n+2); print $20 }' "/proc/$pid/stat" 2>/dev/null)
    [ -n "$start" ] || continue
    grep -q "\"procStart\":\"$start\"" "$s" || continue
    sid=$(grep -o '"sessionId":"[^"]*"' "$s" | head -1 | cut -d'"' -f4)
    [ -n "$sid" ] && printf 'LIVE\t%s\n' "$sid"
  done
fi
for f in {glob}; do
  [ -f "$f" ] || continue
  printf '%s\t%s\t%s\t%s\t%s\t' "$(stat -c %Y "$f" 2>/dev/null || echo 0)" \
    "$(wc -l < "$f")" "$(stat -c %s "$f" 2>/dev/null || echo 0)" \
    "$(grep -o '"usage":{[^}]*' "$f" 2>/dev/null | tail -1)" "$f"
  grep '"type":"custom-title"' "$f" 2>/dev/null | tail -1 | tr '\n' '\037'
  grep '"type":"user"' "$f" 2>/dev/null | grep -v '"tool_use_id"' | tail -12 | tr '\n' '\037'
  printf '\n'
done
"#;

/// Rows out of what [`listing_script`] printed, with `in_use` filled in.
fn parse_listing(found: &str) -> Result<Vec<Importable>> {
    let mut live = std::collections::HashSet::new();
    let mut checkable = false;
    for line in found.lines() {
        if line.trim() == "LIVEKNOWN" {
            checkable = true;
        } else if let Some(id) = line.strip_prefix("LIVE\t") {
            live.insert(id.trim().to_string());
        }
    }

    let mut sessions: Vec<Importable> = found.lines().filter_map(parse_row).collect();
    for session in &mut sessions {
        session.in_use = match (checkable, live.contains(&session.id)) {
            (_, true) => InUse::Yes,
            (true, false) => InUse::No,
            (false, false) => InUse::Unknown,
        };
    }
    // One row per session id, because the id is what everything downstream
    // addresses: `--resume` takes it, deleting globs for it, and the
    // in-flight registry is keyed on it. So two rows sharing an id are two
    // rows that no operation can tell apart -- and the phone keys its list
    // on it too, which turned this into a crash rather than a confusion.
    //
    // It is a real state of the machine, not corruption: resuming a session
    // from a different working directory makes the CLI write a second file
    // under that directory's project folder with the same id. One of the two
    // is then usually a stub of a few hundred bytes and the other is the
    // conversation somebody means.
    //
    // So the copy with the most in it wins, and the row's `cwd` comes from
    // that same copy -- which is the directory `--resume` will find it under.
    // Ties go to the more recent, and the *stub* is often the more recent, so
    // the size has to be the first key rather than the tie-break.
    sessions.sort_by(|a, b| {
        b.lines
            .cmp(&a.lines)
            .then_with(|| b.modified.total_cmp(&a.modified))
    });
    let mut seen = std::collections::HashSet::new();
    sessions.retain(|session| seen.insert(session.id.clone()));

    // Most recent first, and only that. Naming was tried as the first key
    // and is a worse list: it buries what somebody was just doing under
    // everything they ever named, and the reason to open this screen is
    // almost always to pick up where they left off. A name still shows,
    // as the row's title and as a word beside it -- being easier to
    // recognise is what a name is for, and it does not need the order too.
    sessions.sort_by(|a, b| b.modified.total_cmp(&a.modified));
    Ok(sessions)
}

/// One line of [`list`]'s output, or nothing if it is not one.
fn parse_row(line: &str) -> Option<Importable> {
    let mut fields = line.splitn(6, '\t');
    let modified: f64 = fields.next()?.trim().parse().ok()?;
    let lines: usize = fields.next()?.trim().parse().ok()?;
    let bytes: u64 = fields.next()?.trim().parse().ok()?;
    let context_tokens = context_tokens(fields.next()?);
    let path = fields.next()?.to_string();
    let id = path.rsplit('/').next()?.strip_suffix(".jsonl")?.to_string();

    let mut named = None;
    let mut said = None;
    let mut cwd = None;
    for record in fields
        .next()
        .unwrap_or("")
        .split('\u{1f}')
        .filter_map(|record| serde_json::from_str::<Value>(record).ok())
    {
        if cwd.is_none() {
            cwd = record.get("cwd").and_then(Value::as_str).map(String::from);
        }
        if let Some(custom) = record.get("customTitle").and_then(Value::as_str) {
            named = Some(custom.to_string());
            continue;
        }
        if !is_hidden(&record)
            && let Some(text) = first_line_of(&record)
        {
            // Kept rather than broken out of: these arrive oldest first,
            // so the last one to survive the filter is the most recent
            // thing that was actually said.
            said = Some(text);
        }
    }

    Some(Importable {
        id,
        // Filled in by `list`, which is the only thing that knows: it
        // takes one command to ask a machine, and asking per row would be
        // one ssh connection each.
        in_use: InUse::Unknown,
        cwd: cwd.unwrap_or_default(),
        // A name somebody typed outranks anything read out of the
        // conversation, because they chose it to answer this exact
        // question.
        named: named.is_some(),
        title: named
            .or(said)
            .unwrap_or_else(|| "(no messages)".to_string()),
        modified,
        lines,
        bytes,
        context_tokens,
        path,
    })
}

/// The input tokens named in one `usage` object, added up.
///
/// Prompt plus cache creation plus cache read: all three are context the
/// model was given -- the definition is [`driver::context_tokens`]; this
/// is the same three figures dug out of a raw line rather than a parsed
/// one, because these files reach tens of megabytes.
///
/// `None` for an empty blob, meaning no assistant turn has recorded usage.
/// Missing individual fields count as zero, which is what an absent
/// category means; an unparseable one does the same rather than
/// discarding the figures that did read.
fn context_tokens(usage: &str) -> Option<u64> {
    if usage.trim().is_empty() {
        return None;
    }
    // The leading quote matters: without it `"input_tokens"` also matches
    // inside `"cache_read_input_tokens"`, and the same number gets counted
    // three times.
    let field = |name: &str| -> u64 {
        usage
            .split_once(&format!("\"{name}\":"))
            .map(|(_, rest)| rest.trim_start())
            .and_then(|rest| {
                let digits: String = rest.chars().take_while(char::is_ascii_digit).collect();
                digits.parse().ok()
            })
            .unwrap_or(0)
    };
    Some(driver::context_tokens(
        field("input_tokens"),
        field("cache_creation_input_tokens"),
        field("cache_read_input_tokens"),
    ))
}

/// The first line of what a person typed, short enough for a list row.
///
/// None for the CLI's own plumbing. A slash command, the caveat wrapped
/// around a local command's output, and an injected reminder are all
/// stored as ordinary user records without the `isMeta` flag -- so titling
/// by "first user record" gave a list where most rows read
/// `<command-name>/clear</command-name>`, which identifies nothing. The
/// caller offers several candidates for exactly this reason.
fn first_line_of(record: &Value) -> Option<String> {
    let text = text_of(record.get("message")?.get("content")?);
    let first = text.lines().find(|line| !line.trim().is_empty())?.trim();
    if first.starts_with('<') {
        return None;
    }
    let trimmed: String = first.chars().take(90).collect();
    (!trimmed.is_empty()).then_some(trimmed)
}

/// Records the transcript should not show: a subagent's private
/// conversation, and the CLI's own injected notes.
///
/// The same rule the live translator applies -- a sidechain is another
/// agent talking to itself, and duplicating it into this transcript would
/// show the reader two conversations interleaved as one.
fn is_hidden(record: &Value) -> bool {
    record.get("isSidechain").and_then(Value::as_bool) == Some(true)
        || record.get("isMeta").and_then(Value::as_bool) == Some(true)
}

/// Concatenated text of a message's content, which is either a bare string
/// or the API's list of blocks.
fn text_of(content: &Value) -> String {
    match content {
        Value::String(text) => text.clone(),
        Value::Array(blocks) => blocks
            .iter()
            .filter(|block| block.get("type").and_then(Value::as_str) == Some("text"))
            .filter_map(|block| block.get("text").and_then(Value::as_str))
            .collect::<Vec<_>>()
            .join("\n"),
        _ => String::new(),
    }
}

/// Whether a directory the machine recorded is still there.
///
/// Asked because a session's recorded cwd can outlive the directory: these
/// files go back months, and a checkout that moved leaves every session
/// from before the move pointing at a path that is gone. Resuming into one
/// fails at `cd` before the CLI starts, which is a confusing way to meet a
/// feature whose whole promise is "carry on where you left off".
pub async fn directory_exists(transport: &Transport, path: &str) -> bool {
    if path.is_empty() {
        return false;
    }
    // Asked by *entering* it rather than by `test -d <path>`, because the
    // question this is standing in for is "can a session start here" and
    // because a path is only expanded where it is a working directory --
    // `~/repos/ai-app` as an argument stays four literal characters on
    // both transports (`ssh::quote_path`, `ssh::expand_home`), so the old
    // form answered "no such directory" about every home-relative path
    // somebody typed.
    let launch = Launch::new("true", Vec::new(), Some(std::path::Path::new(path)));
    transport.capture(&launch).await.is_ok()
}

/// Reads the tail of one session's file, as the raw JSONL.
///
/// `tail` rather than the whole file, and as [`Launch`] arguments rather
/// than a shell string, so the path is an argument and never syntax.
///
/// Returns text rather than events because turning records into events has
/// a side effect -- writing out the images they carry -- and it needs the
/// session directory to write them into. That directory does not exist
/// until the session is created, which is after this runs, so the
/// conversion happens there instead. See [`events_from`].
pub async fn read_tail(transport: &Transport, path: &str) -> Result<String> {
    let launch = Launch::new(
        "tail",
        vec!["-n".to_string(), REPLAY_LINES.to_string(), path.to_string()],
        None,
    );
    transport
        .capture(&launch)
        .await
        .with_context(|| format!("reading {path}"))
}

/// Claude Code's stored JSONL as this project's events.
///
/// A partial first line is expected and ignored: `tail -n` cuts at a line
/// boundary, but the *file* may have been appended to since, and a line
/// that does not parse is one this reader has no opinion about.
///
/// `session_dir` is where images found along the way are written, the same
/// place and by the same function the live translator uses -- so a
/// screenshot looks identical whether it was watched as it happened or
/// replayed afterwards. It is only the *reference* that reaches the phone;
/// the bytes are fetched from `/sessions/{id}/files/{ref}` when something
/// actually draws them, and none of this is ever sent back to the CLI,
/// which reads its own session file.
pub fn events_from(text: &str, session_dir: &std::path::Path) -> Vec<Event> {
    let mut events = Vec::new();
    // What the newest record that had an opinion says the session is
    // doing. Kept to the end rather than pushed as it is found, because
    // the answer is the last one and everything before it is history.
    let mut state = None;
    for line in text.lines() {
        let Ok(record) = serde_json::from_str::<Value>(line) else {
            continue;
        };
        if let Some(peer) = peer_message(&record) {
            // Before `is_hidden`, which these records are: the CLI marks
            // them meta because they are not the user's own words, and
            // that is the reason to draw them differently rather than the
            // reason to drop them. A session working on something a phone
            // never asked for is otherwise unexplainable from the phone.
            state = turn_state(&record).or(state);
            events.push(peer);
            continue;
        }
        if is_hidden(&record) {
            continue;
        }
        state = turn_state(&record).or(state);
        let Some(message) = record.get("message") else {
            continue;
        };
        let Some(content) = message.get("content") else {
            continue;
        };
        match record.get("type").and_then(Value::as_str) {
            Some("user") => push_user(&mut events, content, session_dir),
            Some("assistant") => push_assistant(&mut events, content),
            _ => {}
        }
    }
    if let Some(state) = state {
        events.push(Event::Status { state });
    }
    events
}

/// A message from another agent, as the CLI reports one.
///
/// Measured from a real session file (2026-08-29): the record is a `user`
/// one marked `isMeta`, and its `origin` carries `kind: "peer"`, the
/// sending session's `name`, and the message itself as `body`. The
/// message content beside it is the same text wrapped in an explanatory
/// preamble and a `<cross-session-message>` tag, which is written for the
/// model that has to read it rather than for a person -- so the body is
/// what a reader is shown, and the name is who they are told sent it.
///
/// Shared with the live driver (`claude::translate`), which finds the same
/// `origin` object on a different record -- so this reads the object and
/// not the record around it. One function because it is one wire format:
/// two copies would drift the first time the CLI renames a field, and the
/// half that drifted would go on producing nothing at all, which is
/// indistinguishable from nobody having sent anything.
pub(in crate::session) fn peer_message(record: &Value) -> Option<Event> {
    let origin = record.get("origin")?;
    if origin.get("kind").and_then(Value::as_str) != Some("peer") {
        return None;
    }
    Some(Event::PeerMessage {
        from: origin
            .get("name")
            .and_then(Value::as_str)
            .unwrap_or("another session")
            .to_string(),
        text: origin.get("body").and_then(Value::as_str)?.to_string(),
        // The session file has it in the right place already.
        turn_start: None,
    })
}

/// Whether this record means the session is working, as far as it can be
/// told from the file.
///
/// The one thing a session file does not contain is the CLI saying "this
/// turn is over": there is no `result` record, only the messages. What
/// there is instead is why the last assistant message stopped, and that
/// answers it -- `tool_use` means a call is being made and more is coming,
/// anything else means the model has finished talking. Anything on the
/// user's side of the conversation -- a person, a tool's result, another
/// agent -- means the session has something to answer and is answering it.
///
/// `None` is the third answer and it matters: a record that says nothing
/// about the turn leaves the status alone rather than voting for idle. The
/// same goes for a record whose reason for stopping is missing, which is
/// what a future CLI adding a shape we do not know looks like.
///
/// What this cannot see is a session that stopped existing mid-turn -- its
/// file's last record still says `tool_use`, so it reads as working
/// forever. Nothing in the file distinguishes that from a model thinking,
/// and inventing a timeout here would replace a stale reading with a
/// confident wrong one.
fn turn_state(record: &Value) -> Option<super::driver::SessionStatus> {
    use super::driver::SessionStatus;
    match record.get("type").and_then(Value::as_str)? {
        "user" => Some(SessionStatus::Running),
        "assistant" => match record["message"]
            .get("stop_reason")
            .and_then(Value::as_str)?
        {
            "tool_use" => Some(SessionStatus::Running),
            _ => Some(SessionStatus::Idle),
        },
        _ => None,
    }
}

fn push_user(events: &mut Vec<Event>, content: &Value, session_dir: &std::path::Path) {
    // A tool result arrives as a user record, because that is how the API
    // models it -- but it is the other half of a tool call, not something
    // a person said, and showing it as a message would put the reader's
    // own words and a command's output in the same voice.
    if let Value::Array(blocks) = content {
        for block in blocks {
            // A picture the person attached to their own message, rather
            // than one a tool produced. Same block shape, one level up.
            push_images(events, std::slice::from_ref(block), session_dir, None);
            if block.get("type").and_then(Value::as_str) == Some("tool_result")
                && let Some(id) = block.get("tool_use_id").and_then(Value::as_str)
            {
                // Before the tool's own row, matching the live translator:
                // a screenshot belongs to the call that took it, and after
                // the result it reads as belonging to whatever came next.
                if let Some(Value::Array(parts)) = block.get("content") {
                    push_images(events, parts, session_dir, Some(id));
                }
                events.push(Event::ToolEnd {
                    id: id.to_string(),
                    output: text_of(block.get("content").unwrap_or(&Value::Null)),
                });
            }
        }
    }
    let text = text_of(content);
    if !text.trim().is_empty() {
        // Replayed from the CLI's own file: it was read long ago, so
        // there is no waiting bubble for it to resolve.
        // The images in this record are saved and referenced separately just
        // above, because a replayed message's pictures came out of somebody
        // else's file rather than out of this app's composer -- there is no
        // upload here whose refs could ride on the message.
        events.push(Event::UserMessage {
            id: None,
            text,
            attachments: Vec::new(),
        });
    }
}

/// Saves every image block in `parts` and references each one.
///
/// `about` is the call the images came out of, or `None` for one a person attached
/// to their own message -- the same distinction the live translator makes, so replayed
/// history draws a screenshot under the call that took it exactly as a live one does.
fn push_images(
    events: &mut Vec<Event>,
    parts: &[Value],
    session_dir: &std::path::Path,
    about: Option<&str>,
) {
    for part in parts {
        if part.get("type").and_then(Value::as_str) == Some("image")
            && let Some(name) = super::claude::translate::save_image(session_dir, part)
        {
            events.push(Event::Image {
                image: name,
                about: about.map(String::from),
            });
        }
    }
}

fn push_assistant(events: &mut Vec<Event>, content: &Value) {
    let Value::Array(blocks) = content else {
        return;
    };
    for block in blocks {
        match block.get("type").and_then(Value::as_str) {
            Some("text") => {
                if let Some(text) = block.get("text").and_then(Value::as_str)
                    && !text.is_empty()
                {
                    events.push(Event::AssistantText {
                        delta: text.to_string(),
                    });
                }
            }
            Some("tool_use") => {
                if let (Some(id), Some(name)) = (
                    block.get("id").and_then(Value::as_str),
                    block.get("name").and_then(Value::as_str),
                ) {
                    events.push(Event::ToolStart {
                        id: id.to_string(),
                        tool: name.to_string(),
                        input: block.get("input").cloned().unwrap_or(Value::Null),
                    });
                }
            }
            _ => {}
        }
    }
}

/// Removes each id it is given and prints one `<id>\t<state>` line per id.
///
/// The three states are every way removing one id can end: `deleted` if at
/// least one file went, `missing` if the glob matched nothing, `failed` if
/// an `rm` refused. "Not there" is deliberately kept apart from "it broke"
/// rather than folded together by the shell -- only one of them is worth
/// retrying, and the caller is what knows how to word either.
///
/// Every copy of each id, not the first. The same id can name a file under
/// two project directories -- see the de-duplication in `parse_listing` --
/// and stopping at the first left the other behind, so the row came back on
/// the next listing after a delete that had reported success. `failed`
/// therefore sticks once set: one copy removed and another refused is not a
/// success.
///
/// Ids arrive as arguments rather than in the script text, so nothing here
/// is shell syntax; `is_session_id` is what keeps one from globbing its way
/// out of the projects directory.
const DELETE_SCRIPT: &str = r#"
for id do
  state=missing
  for f in "$HOME"/.claude/projects/*/"$id".jsonl; do
    [ -f "$f" ] || continue
    if rm -f "$f"; then
      [ "$state" = failed ] || state=deleted
    else
      state=failed
    fi
  done
  printf '%s\t%s\n' "$id" "$state"
done
"#;

/// Deletes sessions [`list`] reported, and says what happened to each.
///
/// By id, resolved on the machine against what it actually has, so the
/// caller never names a file -- the same rule importing follows, and it
/// matters more here: this one removes something.
///
/// Irreversible, and the caller is expected to have said so. Claude Code
/// keeps no copy: the JSONL *is* the session, so deleting it ends any
/// chance of resuming that conversation, including from an ai-app session
/// that was already importing it.
///
/// The whole batch in one invocation, which over ssh is the difference
/// between one connection and one per session. Six deletes started in the
/// same tick were six `ssh` processes racing to authenticate, and a batch
/// big enough to pass the remote sshd's `MaxStartups` (10 unauthenticated
/// connections, by default, before it begins refusing) had rows come back
/// as `Connection closed by … port 2222` -- a row reporting a delete that
/// never ran, for a reason that has nothing to do with the session. One
/// connection cannot exceed that however many ids are selected.
///
/// Still one outcome per id, because a batch is not a transaction: six
/// removals that must all succeed or all roll back is not something a
/// filesystem offers, and the caller settles each row from its own line.
/// Every requested id gets an entry, so an id the machine said nothing
/// about is reported as such rather than defaulting to either answer.
pub async fn delete(
    transport: &Transport,
    ids: &[String],
) -> Result<HashMap<String, Result<(), String>>> {
    // Refused here rather than on the machine: `is_session_id` is what
    // keeps an id from walking out of the projects directory, and a bad
    // one must never reach the glob. It fails only itself -- one malformed
    // id is not a reason to leave the other five in place.
    let (safe, mut outcomes): (Vec<&String>, HashMap<String, Result<(), String>>) =
        ids.iter().fold(
            (Vec::new(), HashMap::new()),
            |(mut safe, mut outcomes), id| {
                if is_session_id(id) {
                    safe.push(id);
                } else {
                    outcomes.insert(
                        id.clone(),
                        Err(format!("not a Claude Code session id: {id}")),
                    );
                }
                (safe, outcomes)
            },
        );
    if safe.is_empty() {
        return Ok(outcomes);
    }

    // The file name *is* the id, so the machine can find it by name. This
    // used to call `list` and search its output, which is correct and costs
    // a full read of every transcript on the machine -- around four seconds
    // against a gigabyte of them, per delete, so a batch of ten took the
    // best part of a minute doing nothing but re-reading the same files.
    // `context_of` below already resolved an id the cheap way; this is the
    // same lookup, and the two now agree.
    //
    // Every copy of each id, not the first. The same id can name a file
    // under two project directories -- see the de-duplication in
    // `parse_listing` -- and stopping at the first left the other behind,
    // so the row came back on the next listing after a delete that had
    // reported success.
    //
    // Each id prints its own verdict rather than the loop exiting on the
    // first failure: with a batch, exiting would leave every id after it
    // unexplained. See [`DELETE_SCRIPT`] for what the words mean.
    let mut args = vec![
        "-c".to_string(),
        DELETE_SCRIPT.to_string(),
        "sh".to_string(),
    ];
    args.extend(safe.iter().map(|id| (*id).clone()));
    let launch = Launch::new("sh", args, None);

    // A failure to run the script at all is the machine being unreachable,
    // which is true of every id in the batch rather than of any one of
    // them -- so it is returned as the error, not written into each row.
    let reported = transport
        .capture(&launch)
        .await
        .with_context(|| format!("deleting {} Claude Code sessions", safe.len()))?;

    for line in reported.lines() {
        let Some((id, state)) = line.trim().split_once('\t') else {
            continue;
        };
        outcomes.insert(
            id.to_string(),
            match state {
                "deleted" => Ok(()),
                "missing" => Err(format!("no Claude Code session {id} on that machine")),
                _ => Err(format!("couldn't remove Claude Code session {id}")),
            },
        );
    }
    // Anything the machine did not mention. The connection can drop
    // part-way through the loop, and an id whose line never arrived is one
    // nobody knows the fate of -- which is its own answer, and must not be
    // read as either a success or a clean "not there".
    for id in safe {
        outcomes.entry(id.clone()).or_insert_with(|| {
            Err(format!(
                "couldn't tell whether Claude Code session {id} was deleted -- the machine \
                 stopped answering part-way through the batch"
            ))
        });
    }
    Ok(outcomes)
}

/// Whether an id is one of ours to put in a shell glob.
///
/// Both places that resolve an id to a file interpolate it into
/// `$HOME/.claude/projects/*/"$1".jsonl`. That is an argument rather than
/// script text, so a shell cannot be talked into running something -- but a
/// `/` or a `..` inside it still walks the glob out of the directory the id
/// is supposed to name. [`delete`] is where that would be fatal, because it
/// removes whatever it lands on, and it is exactly the reason `delete` used
/// to resolve ids by searching a listing instead.
///
/// Claude Code names each transcript with a uuid, so hex and dashes is the
/// whole alphabet. Refused rather than escaped: an id that is not one of
/// these did not come from the list this app showed.
fn is_session_id(id: &str) -> bool {
    !id.is_empty() && id.len() <= 64 && id.bytes().all(|b| b.is_ascii_hexdigit() || b == b'-')
}

/// How often an imported session checks whether its source file grew.
///
/// A poll rather than a watch, because the file may be on another machine
/// and there is no portable way to be told. Ten seconds is chosen against
/// the cost of an ssh round trip rather than against how fast a person
/// types: nothing here is waiting on it, and the events arrive on the same
/// stream as everything else once they do.
pub const SYNC_INTERVAL: std::time::Duration = std::time::Duration::from_secs(10);

/// Where an imported session came from, and how much of it has been shown.
///
/// Kept beside the session rather than in its config, because it is a
/// position in someone else's file rather than anything the person chose,
/// and it changes constantly.
#[derive(Debug, Clone, Serialize, serde::Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct Cursor {
    /// Server-side only, and resolved once at import. Nothing accepts a
    /// path from the phone; this is the path *we* found.
    pub path: String,
    /// Lines of that file already accounted for -- whether replayed into
    /// the transcript or skipped because this session wrote them itself.
    pub lines: usize,
}

const CURSOR_FILE: &str = "import.json";

pub fn read_cursor(session_dir: &std::path::Path) -> Option<Cursor> {
    let text = std::fs::read_to_string(session_dir.join(CURSOR_FILE)).ok()?;
    serde_json::from_str(&text).ok()
}

pub fn write_cursor(session_dir: &std::path::Path, cursor: &Cursor) {
    let path = session_dir.join(CURSOR_FILE);
    match serde_json::to_string(cursor) {
        Ok(text) => {
            if let Err(err) = std::fs::write(&path, text) {
                tracing::error!(
                    "couldn't persist the import cursor to {}: {err}",
                    path.display()
                );
            }
        }
        Err(err) => tracing::error!("couldn't serialize the import cursor: {err}"),
    }
}

/// How many lines the source file has now.
pub async fn line_count(transport: &Transport, path: &str) -> Result<usize> {
    let launch = Launch::new("wc", vec!["-l".to_string(), path.to_string()], None);
    let out = transport.capture(&launch).await?;
    out.split_whitespace()
        .next()
        .and_then(|n| n.parse().ok())
        .with_context(|| format!("couldn't read a line count out of {out:?}"))
}

/// What the CLI's own file says a session is holding, for a session this
/// server has no measurement of.
///
/// A restarting server has been told nothing, and a session that has not
/// taken a turn since will not tell it -- so a conversation that is nearly
/// full reads as one nobody has counted until somebody sends a message to
/// it. The CLI records the figure on every assistant message, so it is
/// there to be read rather than waited for, and reading it is a
/// measurement rather than a guess: the same three fields, from the same
/// file, that the import list reports.
///
/// A clear needs no special case here even though it makes the last usage
/// in a file stale. Clearing gives the CLI a *new* session id, which the
/// reader persists as the resume token, so this looks in a file that has
/// no usage in it yet and answers `None` -- which is the true answer.
///
/// `None` for every way it cannot be read: no resume token, no file, a
/// machine that cannot be reached, or a file with no assistant turn in it.
/// Not knowing is a state the status row draws, so there is nothing to be
/// gained by inventing a number here.
pub async fn context_of(transport: &Transport, session_id: &str) -> Option<u64> {
    // The same guard `delete` explains, applied to the other member of the
    // set: this one only reads, but a glob that can leave the directory is
    // worth closing in both places rather than in the dangerous one only.
    if !is_session_id(session_id) {
        return None;
    }
    // The id crosses as an argument rather than as script text: it comes
    // from the CLI, but it reaches a shell on a machine that may not be
    // this one, and the rule there is that data never becomes syntax.
    let script = r#"
for f in "$HOME"/.claude/projects/*/"$1".jsonl; do
  [ -f "$f" ] || continue
  grep -o '"usage":{[^}]*' "$f" | tail -1
  exit 0
done
"#;
    let launch = Launch::new(
        "sh",
        vec![
            "-c".to_string(),
            script.to_string(),
            "sh".to_string(),
            session_id.to_string(),
        ],
        None,
    );
    context_tokens(&transport.capture(&launch).await.ok()?)
}

/// Events from the lines after `after`, which is a 0-based count of lines
/// already accounted for.
pub async fn replay_after(
    transport: &Transport,
    path: &str,
    after: usize,
    session_dir: &std::path::Path,
) -> Result<Vec<Event>> {
    let launch = Launch::new(
        "tail",
        vec![format!("-n+{}", after + 1), path.to_string()],
        None,
    );
    let text = transport
        .capture(&launch)
        .await
        .with_context(|| format!("reading {path} from line {}", after + 1))?;
    Ok(events_from(&text, session_dir))
}

#[cfg(test)]
mod tests {
    use super::*;

    /// One session id, two files, one row.
    ///
    /// Resuming a session from a different working directory makes the CLI
    /// write a second file with the same id under that directory's project
    /// folder, so this is an ordinary state of a machine rather than a
    /// corrupt one. Everything downstream addresses a session by id, and
    /// the phone keys its list on it, so two rows sharing one was a crash.
    ///
    /// The stub is deliberately the *newer* of the two here, because that
    /// is how the real case looked: ordering by recency alone picks the
    /// near-empty copy and describes the session by the wrong cwd.
    #[test]
    fn a_session_recorded_under_two_projects_is_offered_once() {
        let id = "3114dee1-2f95-4de0-9c04-3d6fcc594afe";
        let said = r#"{"cwd":"/home/bob/repos/survey","message":{"role":"user","content":"the real conversation"}}"#;
        let stub = r#"{"cwd":"/home/bob/repos/elsewhere","message":{"role":"user","content":"resumed here once"}}"#;
        let listing = format!(
            "LIVEKNOWN\n\
             1000.0\t412\t160638\t\t/home/bob/.claude/projects/-home-bob-repos-survey/{id}.jsonl\t{said}\n\
             2000.0\t4\t614\t\t/home/bob/.claude/projects/-home-bob-repos-elsewhere/{id}.jsonl\t{stub}\n"
        );

        let rows = parse_listing(&listing).expect("parse");

        assert_eq!(rows.len(), 1, "one id is one row: {rows:#?}");
        assert_eq!(rows[0].lines, 412, "the conversation, not the stub");
        // The cwd has to come from the copy that was kept, because that is
        // the directory `--resume` will find those 412 lines under.
        assert_eq!(rows[0].cwd, "/home/bob/repos/survey");
    }

    /// The guard on the only thing this module ever puts in a glob.
    ///
    /// Worth a test of its own because what it protects is a `rm`: `delete`
    /// resolves an id straight to `$HOME/.claude/projects/*/"$1".jsonl`, so
    /// an id that can contain a slash or a `..` is an id that can name a
    /// file outside the directory and have it removed.
    #[test]
    fn a_session_id_cannot_walk_out_of_the_projects_directory() {
        assert!(is_session_id("5ecf21da-d53f-4a11-9c0d-000000000100"));
        assert!(is_session_id("deadbeef"));

        assert!(!is_session_id("../../../etc/passwd"));
        assert!(!is_session_id("a/b"));
        assert!(!is_session_id(".."));
        assert!(!is_session_id("a.b"));
        assert!(!is_session_id("a*"));
        assert!(!is_session_id("a b"));
        // Empty would glob to the directory itself, and a long one is not a
        // uuid whatever else it is.
        assert!(!is_session_id(""));
        assert!(!is_session_id(&"a".repeat(65)));
    }

    /// One batch, one invocation, one verdict per id -- including for the
    /// two cases a single-id delete never had to keep apart from the rest:
    /// an id recorded under two project directories (both copies must go,
    /// and it still reports once) and an id that is not there at all.
    ///
    /// Runs the real script against a temporary `$HOME`, because what is
    /// being checked is the shell, not the Rust around it.
    #[test]
    fn a_batch_deletes_every_copy_and_reports_each_id_once() {
        let home = tempfile::tempdir().expect("tempdir");
        let projects = home.path().join(".claude/projects");
        let one = "5ecf21da-d53f-4a11-9c0d-000000000100";
        let twice = "5ecf21da-d53f-4a11-9c0d-000000000200";
        let absent = "5ecf21da-d53f-4a11-9c0d-000000000300";
        for (project, id) in [("a", one), ("a", twice), ("b", twice)] {
            let dir = projects.join(project);
            std::fs::create_dir_all(&dir).expect("project dir");
            std::fs::write(dir.join(format!("{id}.jsonl")), "{}\n").expect("transcript");
        }

        let output = std::process::Command::new("sh")
            .args(["-c", DELETE_SCRIPT, "sh", one, twice, absent])
            .env("HOME", home.path())
            .output()
            .expect("run the delete script");
        assert!(output.status.success());

        assert_eq!(
            String::from_utf8_lossy(&output.stdout),
            format!("{one}\tdeleted\n{twice}\tdeleted\n{absent}\tmissing\n"),
        );
        // The second copy is the one a per-id delete used to leave behind.
        assert!(!projects.join("b").join(format!("{twice}.jsonl")).exists());
        assert!(!projects.join("a").join(format!("{twice}.jsonl")).exists());
        assert!(!projects.join("a").join(format!("{one}.jsonl")).exists());
    }

    /// A 1x1 PNG, base64 -- the smallest thing with a real header.
    const PNG: &str = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk\
                       YPhfDwAChwGA60e6kgAAAABJRU5ErkJggg==";

    #[test]
    fn replayed_screenshots_are_saved_and_referenced() {
        let dir = tempfile::tempdir().expect("tempdir");
        // The shape a screenshot actually has in these files: an image
        // part inside a tool result, beside its text.
        let line = format!(
            r#"{{"type":"user","message":{{"role":"user","content":[{{"type":"tool_result","tool_use_id":"toolu_1","content":[{{"type":"text","text":"took a screenshot"}},{{"type":"image","source":{{"type":"base64","media_type":"image/png","data":"{PNG}"}}}}]}}]}}}}"#
        );

        let events = events_from(&line, dir.path());
        let Some(Event::Image { image, .. }) = events.first() else {
            panic!("a replayed screenshot must become an image event: {events:?}");
        };
        assert!(image.ends_with(".png"));
        // On disk, where the files route serves it from -- the phone
        // fetches it only when something draws it.
        assert!(dir.path().join("files").join(image).is_file());

        // And it comes before the tool row it belongs to, so it does not
        // read as belonging to whatever happened next.
        assert!(
            matches!(events.get(1), Some(Event::ToolEnd { .. })),
            "{events:?}"
        );
    }

    #[test]
    fn context_tokens_add_the_input_side_only() {
        // The shape the CLI records, as captured from a real transcript.
        let usage = r#""usage":{"input_tokens":2,"cache_creation_input_tokens":703,"cache_read_input_tokens":142228,"output_tokens":587,"output_tokens_details":{"thinking_tokens":0"#;
        // 2 + 703 + 142228. Output is not context to carry forward, so it
        // is not in the total; if it were, this would read 143520.
        assert_eq!(context_tokens(usage), Some(142_933));

        // The leading quote is load-bearing: without it "input_tokens"
        // matches inside both cache field names and the prompt figure gets
        // counted three times.
        let only_cache = r#""usage":{"cache_read_input_tokens":100,"output_tokens":9"#;
        assert_eq!(context_tokens(only_cache), Some(100));

        // No assistant turn yet is not a context of zero.
        assert_eq!(context_tokens(""), None);
        assert_eq!(context_tokens("   "), None);
    }

    #[test]
    fn a_record_with_no_image_writes_nothing() {
        let dir = tempfile::tempdir().expect("tempdir");
        let line = r#"{"type":"user","message":{"role":"user","content":[{"type":"tool_result","tool_use_id":"toolu_1","content":"plain output"}]}}"#;
        let events = events_from(line, dir.path());
        // The result, and the turn state it implies: a tool has answered,
        // so the model is about to be asked again.
        assert_eq!(events.len(), 2, "{events:?}");
        assert_eq!(
            events[1],
            Event::Status {
                state: super::super::driver::SessionStatus::Running
            }
        );
        // No stray directory for a session that never produced one.
        assert!(!dir.path().join("files").exists());
    }

    #[test]
    fn a_message_from_another_agent_is_kept_and_named() {
        // The real shape, from a session file: the CLI marks these meta,
        // and everything a reader needs is in `origin`.
        let dir = tempfile::tempdir().expect("tempdir");
        let line = r#"{"type":"user","isMeta":true,"origin":{"kind":"peer","from":"uds:/run/user/1000/cc-socks/605.sock","verifiedPeerPid":605,"name":"dev-updater-f5","fromMode":"prompting","body":"Pull before you touch AGENTS.md."},"message":{"role":"user","content":"Another Claude session sent a message:\n<cross-session-message from-name=\"dev-updater-f5\">\nPull before you touch AGENTS.md.\n</cross-session-message>"}}"#;
        let events = events_from(line, dir.path());
        assert_eq!(
            events[0],
            Event::PeerMessage {
                from: "dev-updater-f5".to_string(),
                // The body, not the wrapper the model is given.
                text: "Pull before you touch AGENTS.md.".to_string(),
                turn_start: None,
            },
            "{events:?}"
        );
        // And it counts as the session having been given something.
        assert_eq!(
            events[1],
            Event::Status {
                state: super::super::driver::SessionStatus::Running
            }
        );
    }

    #[test]
    fn the_last_record_says_whether_the_session_is_working() {
        use super::super::driver::SessionStatus;
        let dir = tempfile::tempdir().expect("tempdir");
        let asked = r#"{"type":"user","message":{"role":"user","content":"do the thing"}}"#;
        let calling = r#"{"type":"assistant","message":{"role":"assistant","stop_reason":"tool_use","content":[{"type":"tool_use","id":"t1","name":"Bash","input":{}}]}}"#;
        let done = r#"{"type":"assistant","message":{"role":"assistant","stop_reason":"end_turn","content":[{"type":"text","text":"done"}]}}"#;

        let state = |text: &str| {
            events_from(text, dir.path())
                .into_iter()
                .rev()
                .find_map(|event| match event {
                    Event::Status { state } => Some(state),
                    _ => None,
                })
        };
        assert_eq!(state(asked), Some(SessionStatus::Running));
        assert_eq!(
            state(&[asked, calling].join("\n")),
            Some(SessionStatus::Running)
        );
        assert_eq!(
            state(&[asked, calling, done].join("\n")),
            Some(SessionStatus::Idle),
            "a turn that has finished talking is over"
        );

        // A subagent's own messages are not the session's turn, and a
        // record with no stop reason is not an answer -- neither may
        // overrule what the conversation itself last said.
        let sidechain = r#"{"type":"assistant","isSidechain":true,"message":{"role":"assistant","stop_reason":"end_turn","content":[{"type":"text","text":"sub"}]}}"#;
        let unknown = r#"{"type":"assistant","message":{"role":"assistant","content":[{"type":"text","text":"?"}]}}"#;
        assert_eq!(
            state(&[asked, calling, sidechain, unknown].join("\n")),
            Some(SessionStatus::Running)
        );

        // And nothing at all to go on says nothing, rather than idle.
        assert_eq!(state(r#"{"type":"summary","summary":"x"}"#), None);
    }
}