use anyhow::Result;

use crate::config::{DriverKind, ProviderConfig};
use crate::session::transport::{Launch, Transport};

const PROBES: &[(&str, &str, DriverKind)] = &[
    ("claude-cli", "claude", DriverKind::ClaudeCli),
    ("llama-cpp", "llama-server", DriverKind::LlamaCpp),
];

const CLAUDE_MODELS: &[&str] = &["fable", "opus", "sonnet", "haiku"];

/// One round trip rather than one per program: over ssh each would be a separate
/// connection and handshake. `command -v` is POSIX and a shell builtin, so it
/// works whatever is installed -- and `|| true` keeps a missing program from
/// ending the loop, since the caller wants the whole answer.
pub async fn discover(transport: &Transport) -> Result<Vec<ProviderConfig>> {
    let wanted: Vec<&str> = PROBES.iter().map(|(_, binary, _)| *binary).collect();
    let script = format!(
        "for p in {}; do command -v \"$p\" || true; done",
        wanted.join(" ")
    );
    let launch = Launch::new("sh", vec!["-c".to_string(), script], None);
    let found = transport.capture(&launch).await.map_err(explain)?;

    let mut providers = Vec::new();
    if matches!(transport, Transport::Here) {
        providers.push(ProviderConfig {
            name: crate::config::ECHO_PROVIDER.to_string(),
            kind: DriverKind::Echo,
            command: None,
            models: Vec::new(),
        });
    }
    for (name, binary, kind) in PROBES {
        let path = found
            .lines()
            .map(str::trim)
            .find(|line| line.rsplit('/').next() == Some(*binary));
        let Some(path) = path else {
            continue;
        };
        providers.push(ProviderConfig {
            name: (*name).to_string(),
            kind: *kind,
            command: Some(path.to_string()),
            models: match kind {
                DriverKind::ClaudeCli => CLAUDE_MODELS.iter().map(|m| (*m).to_string()).collect(),
                _ => Vec::new(),
            },
        });
    }
    Ok(providers)
}

fn explain(err: anyhow::Error) -> anyhow::Error {
    let message = format!("{err:#}");
    if message.contains("Host key verification failed") {
        return anyhow::anyhow!(
            "{message} This machine has not been connected to before, so its key is not \
             trusted yet. Ssh to it once from the backend -- that is where the decision to \
             trust a key belongs -- and try again.",
        );
    }
    if message.contains("Permission denied") {
        return anyhow::anyhow!(
            "{message} The key named here has to be authorized on that machine, and the path \
             is read on the backend rather than on the phone.",
        );
    }
    err
}

/// A short, stable, filename-safe id derived from a label. Derived once when a
/// setup is added and then fixed, so the label stays editable. Collisions are
/// resolved by the caller, which is the only place that knows what exists.
pub fn id_from(label: &str) -> String {
    let slug: String = label
        .chars()
        .map(|c| {
            if c.is_ascii_alphanumeric() {
                c.to_ascii_lowercase()
            } else {
                '-'
            }
        })
        .collect();
    let slug = slug.trim_matches('-').replace("--", "-");
    if slug.is_empty() {
        crate::session::random_hex()
    } else {
        slug.chars().take(32).collect()
    }
}

pub fn tidy(value: &str) -> Option<String> {
    let value = value.trim();
    if value.is_empty() {
        return None;
    }
    Some(match value.strip_prefix("~/") {
        Some(rest) => match std::env::home_dir() {
            Some(home) => home.join(rest).to_string_lossy().into_owned(),
            None => value.to_string(),
        },
        None => value.to_string(),
    })
}

pub fn shorten_home(path: &str) -> String {
    let Some(home) = std::env::home_dir() else {
        return path.to_string();
    };
    let home = home.to_string_lossy();
    match path.strip_prefix(home.as_ref()) {
        Some("") => "~".to_string(),
        Some(rest) if rest.starts_with('/') => format!("~{rest}"),
        _ => path.to_string(),
    }
}

/// The common case of [`Transport::capture_with_input`]: nothing on stdin, a
/// failure reported as the machine's own words (ssh's "Permission denied" is the
/// useful half of why a setup cannot be reached), and the output read as text
/// because every caller here is asking a question whose answer is words.
impl Transport {
    pub async fn capture(&self, launch: &Launch) -> Result<String> {
        let captured = self
            .capture_with_input(launch, super::session::transport::Input::None)
            .await?;
        Ok(String::from_utf8_lossy(&captured.ok()?).into_owned())
    }
}

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

    #[test]
    fn a_home_path_shortens_and_expands_back() {
        let Some(home) = std::env::home_dir() else {
            return;
        };
        let full = home.join("repos/ai-app-2");
        let full = full.to_string_lossy();
        assert_eq!(shorten_home(&full), "~/repos/ai-app-2");
        assert_eq!(shorten_home(&home.to_string_lossy()), "~");
        assert_eq!(tidy("~/repos/ai-app-2").as_deref(), Some(full.as_ref()));

        let sibling = format!("{}-backup/notes", home.to_string_lossy());
        assert_eq!(shorten_home(&sibling), sibling);
        assert_eq!(shorten_home("/etc/hosts"), "/etc/hosts");
    }
}