//! A tool call's input, read rather than dumped -- the port of
//! `ToolInput.kt`'s `parseToolInput`, which is what both the collapsed
//! card's one-line summary and the expanded card's key/value list are
//! derived from.
//!
//! Every tool's input arrives as JSON, and showing it raw makes the reader
//! parse `{"command":"…","timeout":120000}` themselves to find the one
//! line they care about. So the fields that carry the meaning are pulled
//! out, and anything left over is still shown, because dropping a field
//! would be claiming the tool has no other input when it might.
//!
//! Pure, and here rather than in the widget crate, for the reason the rest
//! of this crate exists: the derivation is the same on a phone and on a
//! desktop, and it is testable without a renderer.

use crate::durations::format_millis_text;
use crate::highlight::Language;
use serde_json::{Map, Value};

/// A tool call's input, split into the parts a card draws separately.
#[derive(Debug, Clone, PartialEq, Eq, Default)]
pub struct ToolInput {
    /// The thing that will actually be run or read, if this tool has one.
    pub subject: Option<String>,
    /// The language [`ToolInput::subject`] is written in, for
    /// highlighting.
    pub language: Option<Language>,
    /// The tool's own one-line summary, when it wrote one.
    pub description: Option<String>,
    /// How long the call may take, in the largest units it fits. Shown
    /// apart because it is a limit on the call rather than part of what
    /// the call does.
    pub timeout: Option<String>,
    /// Everything else, as `name: value` lines. Never dropped.
    pub rest: Vec<String>,
}

impl ToolInput {
    /// The one line to show when there is only room for one: what this
    /// call is for.
    pub fn title(&self) -> Option<&str> {
        self.description
            .as_deref()
            .or(self.subject.as_deref())
            // A subject that is only whitespace would draw as an empty
            // summary line, which reads as a tool with nothing to say
            // rather than as one whose subject was blank.
            .filter(|t| !t.trim().is_empty())
    }
}

/// Which field of which tool is the subject.
///
/// A table rather than a chain of `if`s: adding a tool is a row, and the
/// shape stops any of them from being the special case that gets its own
/// code path. Unknown tools fall through to "no subject, everything is
/// rest".
const SUBJECTS: &[(&str, &str, Option<Language>)] = &[
    ("Bash", "command", Some(Language::Shell)),
    ("Read", "file_path", None),
    ("Write", "file_path", None),
    ("Edit", "file_path", None),
    ("Glob", "pattern", None),
    ("Grep", "pattern", None),
    ("WebFetch", "url", None),
];

/// Fields that are the tool's own prose about itself rather than input to
/// it.
const DESCRIPTIONS: &[&str] = &["description", "prompt"];

/// One JSON value as the Kotlin's `JSONObject.optString`/`get` wrote it: a
/// string is its own characters, anything else is its JSON form.
///
/// One function rather than two, because the same coercion decides both
/// what a subject reads as and what a leftover field's value reads as, and
/// two copies would eventually disagree about a number.
fn as_text(value: &Value) -> String {
    match value {
        Value::String(s) => s.clone(),
        other => other.to_string(),
    }
}

fn non_blank(value: Option<&Value>) -> Option<String> {
    let text = as_text(value?);
    (!text.trim().is_empty()).then_some(text)
}

/// Split `input` (a tool call's JSON) into the parts a card draws.
///
/// Input that is not a JSON object -- older transcripts and some tools
/// send a bare string -- is still the input, so it is still shown, as the
/// whole of `rest`.
pub fn parse_tool_input(tool: &str, input: &str) -> ToolInput {
    let Ok(Value::Object(json)) = serde_json::from_str::<Value>(input) else {
        return ToolInput {
            rest: match input.trim().is_empty() {
                true => Vec::new(),
                false => vec![input.to_string()],
            },
            ..ToolInput::default()
        };
    };
    parse_object(tool, &json)
}

fn parse_object(tool: &str, json: &Map<String, Value>) -> ToolInput {
    let (subject_key, language) = SUBJECTS
        .iter()
        .find(|(name, ..)| *name == tool)
        .map(|(_, key, language)| (Some(*key), *language))
        .unwrap_or((None, None));
    let subject = subject_key.and_then(|key| non_blank(json.get(key)));
    let description = DESCRIPTIONS
        .iter()
        .find_map(|key| non_blank(json.get(*key)));
    let timeout = non_blank(json.get("timeout")).map(|t| format_millis_text(&t));

    // Sorted, so the leftovers are in the same order every time this call
    // is drawn rather than in whatever order the JSON happened to arrive
    // in. A field is left out only when it is already drawn somewhere
    // else on the card.
    let mut keys: Vec<&String> = json
        .keys()
        .filter(|k| Some(k.as_str()) != subject_key || subject.is_none())
        .filter(|k| !DESCRIPTIONS.contains(&k.as_str()) || description.is_none())
        .filter(|k| k.as_str() != "timeout" || timeout.is_none())
        .collect();
    keys.sort();
    let rest = keys
        .into_iter()
        .map(|key| format!("{key}: {}", as_text(&json[key])))
        .collect();

    ToolInput {
        subject,
        language,
        description,
        timeout,
        rest,
    }
}

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

    #[test]
    fn each_tool_in_the_table_has_its_own_subject() {
        // One assertion per row of `SUBJECTS`, because the table is the
        // whole of the rule and a row lost in an edit would otherwise
        // only show up as a card with no summary line.
        let cases = [
            ("Bash", r#"{"command":"ls -la"}"#, "ls -la"),
            ("Read", r#"{"file_path":"/tmp/x.rs"}"#, "/tmp/x.rs"),
            ("Write", r#"{"file_path":"/tmp/y.rs"}"#, "/tmp/y.rs"),
            ("Edit", r#"{"file_path":"/tmp/z.rs"}"#, "/tmp/z.rs"),
            ("Glob", r#"{"pattern":"**/*.rs"}"#, "**/*.rs"),
            ("Grep", r#"{"pattern":"fn main"}"#, "fn main"),
            ("WebFetch", r#"{"url":"https://x/y"}"#, "https://x/y"),
        ];
        for (tool, input, expected) in cases {
            let parsed = parse_tool_input(tool, input);
            assert_eq!(parsed.subject.as_deref(), Some(expected), "{tool}");
            assert_eq!(parsed.title(), Some(expected), "{tool}");
            assert!(parsed.rest.is_empty(), "{tool}: {:?}", parsed.rest);
        }
        assert_eq!(
            parse_tool_input("Bash", r#"{"command":"ls"}"#).language,
            Some(Language::Shell),
            "a Bash command is shell, and is the one row that names a language"
        );
    }

    #[test]
    fn a_tools_own_description_is_what_the_one_line_says() {
        // The description wins over the subject: it is the tool's own
        // prose about what this call is for, which is what a reader
        // scanning a collapsed run is looking for.
        let parsed = parse_tool_input(
            "Bash",
            r#"{"command":"cargo test -p iris","description":"Run the iris tests"}"#,
        );
        assert_eq!(parsed.title(), Some("Run the iris tests"));
        assert_eq!(parsed.subject.as_deref(), Some("cargo test -p iris"));
        assert!(parsed.rest.is_empty(), "{:?}", parsed.rest);
    }

    #[test]
    fn a_timeout_is_read_as_a_span_and_kept_apart_from_the_rest() {
        let parsed = parse_tool_input("Bash", r#"{"command":"sleep 500","timeout":480000}"#);
        assert_eq!(parsed.timeout.as_deref(), Some("8m"));
        assert!(parsed.rest.is_empty(), "{:?}", parsed.rest);
    }

    #[test]
    fn every_field_not_drawn_elsewhere_is_still_shown() {
        // The half the "never dropped" promise is about: a tool this
        // build has never heard of has no subject, so *everything* is
        // rest -- and a known tool's extra fields are too.
        let parsed = parse_tool_input(
            "Edit",
            r#"{"file_path":"/a.rs","old_string":"x","new_string":"y","replace_all":true}"#,
        );
        assert_eq!(
            parsed.rest,
            vec![
                "new_string: y".to_string(),
                "old_string: x".to_string(),
                "replace_all: true".to_string(),
            ],
            "sorted, and a non-string value written as JSON"
        );
        let unknown = parse_tool_input("SomeNewTool", r#"{"b":2,"a":"one"}"#);
        assert_eq!(unknown.subject, None);
        assert_eq!(unknown.rest, vec!["a: one".to_string(), "b: 2".to_string()]);
    }

    #[test]
    fn input_that_is_not_an_object_is_still_the_input() {
        // Older transcripts and some tools send a bare string; a card
        // that dropped it would claim the call had no input at all.
        assert_eq!(
            parse_tool_input("Bash", "just a string").rest,
            vec!["just a string".to_string()]
        );
        assert_eq!(parse_tool_input("Bash", "   ").rest, Vec::<String>::new());
        assert_eq!(parse_tool_input("Bash", "").title(), None);
    }

    #[test]
    fn a_blank_subject_is_no_subject_rather_than_an_empty_summary_line() {
        let parsed = parse_tool_input("Bash", r#"{"command":"   ","other":1}"#);
        assert_eq!(parsed.subject, None);
        assert_eq!(parsed.title(), None);
        // Not dropped just because it was blank -- it is still a field
        // the call carried.
        assert_eq!(
            parsed.rest,
            vec!["command:    ".to_string(), "other: 1".to_string()]
        );
    }
}