//! Diagnostics: log level control and the exportable bug-report bundle.
//!
//! TRACES: UR-078 | DR-218
//!
//! The app used to forget everything it did the moment it exited. A user
//! reporting "the episode randomly restarted" was reporting the symptom of a
//! race whose evidence had been discarded microseconds later, and the only way
//! to recover it was to talk them through `adb logcat` — which is how several
//! bugs in this project's history actually got diagnosed.
//!
//! This module is the other half of that: the log is on disk, it survives a
//! crash, and the user can hand the whole thing over as one file.
//!
//! Everything written here has been through [`crate::utils::diagnostics::redact`]
//! twice — once in the log formatter, and again on the way into the archive, so
//! files written by a build that predates the formatter pass are covered too.

use std::fs;
use std::io::{Read, Write};
use std::path::{Path, PathBuf};

use log::{info, warn, LevelFilter};
use serde::{Deserialize, Serialize};
use tauri::{AppHandle, Manager};

use crate::utils::diagnostics::{redact, redact_server_url};

/// Where an export landed, so the UI can tell the user where to find it.
#[derive(Debug, Clone, Serialize, Deserialize, specta::Type)]
#[serde(rename_all = "camelCase")]
pub struct DiagnosticsBundle {
    /// Absolute path to the written archive.
    pub path: String,
    pub size_bytes: u64,
    /// How many log files went in, excluding the environment summary.
    pub file_count: usize,
}

/// Where logs live and how verbose they currently are.
#[derive(Debug, Clone, Serialize, Deserialize, specta::Type)]
#[serde(rename_all = "camelCase")]
pub struct DiagnosticsInfo {
    /// Directory holding the rotating log files.
    pub log_dir: String,
    /// Active level, lowercase: "error" | "warn" | "info" | "debug" | "trace".
    pub level: String,
    /// Total bytes currently held by log files.
    pub total_size_bytes: u64,
}

/// Name of the file holding the user's chosen level, in the app config dir.
const LEVEL_FILE: &str = "log-level";

/// Parse a stored/user-supplied level name.
///
/// Unknown values fall back to Info rather than erroring: this is read at
/// startup, and a corrupt one-line file must not stop the app from launching.
pub fn parse_level(raw: &str) -> LevelFilter {
    match raw.trim().to_ascii_lowercase().as_str() {
        "error" => LevelFilter::Error,
        "warn" => LevelFilter::Warn,
        "debug" => LevelFilter::Debug,
        "trace" => LevelFilter::Trace,
        _ => LevelFilter::Info,
    }
}

/// Read the persisted level, if the user has ever set one.
///
/// Persisted rather than session-only on purpose: somebody reproducing a bug
/// needs debug logging to survive *the restart that reproduces it*.
pub fn stored_level(config_dir: &Path) -> Option<LevelFilter> {
    fs::read_to_string(config_dir.join(LEVEL_FILE))
        .ok()
        .map(|raw| parse_level(&raw))
}

fn level_name(level: LevelFilter) -> &'static str {
    match level {
        LevelFilter::Off => "off",
        LevelFilter::Error => "error",
        LevelFilter::Warn => "warn",
        LevelFilter::Info => "info",
        LevelFilter::Debug => "debug",
        LevelFilter::Trace => "trace",
    }
}

/// Current log level and where the files are.
///
/// TRACES: UR-078 | DR-218
#[tauri::command]
#[specta::specta]
pub async fn diagnostics_get_info(app: AppHandle) -> Result<DiagnosticsInfo, String> {
    let log_dir = app
        .path()
        .app_log_dir()
        .map_err(|e| format!("no log directory: {e}"))?;

    let total_size_bytes = log_files(&log_dir)
        .iter()
        .filter_map(|p| fs::metadata(p).ok())
        .map(|m| m.len())
        .sum();

    Ok(DiagnosticsInfo {
        log_dir: log_dir.to_string_lossy().to_string(),
        level: level_name(log::max_level()).to_string(),
        total_size_bytes,
    })
}

/// Set the log level, for this session and the next.
///
/// TRACES: UR-078 | DR-218
#[tauri::command]
#[specta::specta]
pub async fn diagnostics_set_level(app: AppHandle, level: String) -> Result<String, String> {
    let parsed = parse_level(&level);
    log::set_max_level(parsed);

    let config_dir = app
        .path()
        .app_config_dir()
        .map_err(|e| format!("no config directory: {e}"))?;
    fs::create_dir_all(&config_dir).map_err(|e| e.to_string())?;
    fs::write(config_dir.join(LEVEL_FILE), level_name(parsed)).map_err(|e| e.to_string())?;

    info!("[DIAG] log level set to {}", level_name(parsed));
    Ok(level_name(parsed).to_string())
}

/// Collect every log file in the log directory, newest first.
fn log_files(log_dir: &Path) -> Vec<PathBuf> {
    let Ok(entries) = fs::read_dir(log_dir) else {
        return Vec::new();
    };
    let mut files: Vec<PathBuf> = entries
        .filter_map(|e| e.ok())
        .map(|e| e.path())
        .filter(|p| p.is_file())
        .filter(|p| {
            p.extension()
                .is_some_and(|ext| ext == "log" || ext == "txt")
        })
        .collect();
    files.sort();
    files.reverse();
    files
}

/// A short, non-identifying description of the environment.
///
/// Deliberately excludes the token, the username, and any path outside the
/// app's own directories. The server URL is reduced to scheme and host, which is
/// diagnostic (https? LAN address? reverse proxy?) without being a credential.
fn environment_summary(app: &AppHandle, server_url: Option<&str>) -> String {
    let package = app.package_info();
    let mut out = String::new();
    out.push_str("JellyTau diagnostics\n");
    out.push_str("====================\n\n");
    out.push_str(&format!("app version:   {}\n", package.version));
    out.push_str(&format!("tauri version: {}\n", tauri::VERSION));
    out.push_str(&format!("os:            {}\n", std::env::consts::OS));
    out.push_str(&format!("arch:          {}\n", std::env::consts::ARCH));
    out.push_str(&format!("debug build:   {}\n", cfg!(debug_assertions)));
    out.push_str(&format!(
        "log level:     {}\n",
        level_name(log::max_level())
    ));
    out.push_str(&format!(
        "server:        {}\n",
        server_url.map_or("not configured".to_string(), redact_server_url)
    ));
    out.push_str("\nNo access token, password or username is included in this file.\n");
    out
}

/// Write a redacted diagnostics archive and return where it went.
///
/// # Blocking I/O
///
/// This reads and rewrites every log file. It is an `async` command so it does
/// not block the IPC thread, but it must never be called from a player event
/// callback — see the deadlock note in CLAUDE.md.
///
/// TRACES: UR-078 | DR-218
#[tauri::command]
#[specta::specta]
pub async fn diagnostics_export(
    app: AppHandle,
    server_url: Option<String>,
) -> Result<DiagnosticsBundle, String> {
    let log_dir = app
        .path()
        .app_log_dir()
        .map_err(|e| format!("no log directory: {e}"))?;

    // Written into the app's own data directory. Choosing an arbitrary
    // user-visible location would need a file dialog on desktop and a storage
    // permission on Android; the UI reports the path and can reveal it.
    let out_dir = app
        .path()
        .app_data_dir()
        .map_err(|e| format!("no data directory: {e}"))?;
    fs::create_dir_all(&out_dir).map_err(|e| e.to_string())?;

    let archive_path = out_dir.join("jellytau-diagnostics.zip");
    let file = fs::File::create(&archive_path).map_err(|e| e.to_string())?;
    let mut zip = zip::ZipWriter::new(file);
    let options: zip::write::FileOptions<'_, ()> =
        zip::write::FileOptions::default().compression_method(zip::CompressionMethod::Deflated);

    let files = log_files(&log_dir);
    let mut written = 0usize;

    for path in &files {
        let Some(name) = path.file_name().and_then(|n| n.to_str()) else {
            continue;
        };

        let mut contents = String::new();
        match fs::File::open(path).and_then(|mut f| f.read_to_string(&mut contents)) {
            Ok(_) => {}
            Err(e) => {
                // A log we cannot read is not a reason to produce no bundle.
                warn!("[DIAG] skipping unreadable log {name}: {e}");
                continue;
            }
        }

        // Second redaction pass. The formatter already cleaned anything this
        // build wrote; this covers files left by an older build.
        let cleaned: String = contents.lines().map(redact).collect::<Vec<_>>().join("\n");

        zip.start_file(name, options).map_err(|e| e.to_string())?;
        zip.write_all(cleaned.as_bytes())
            .map_err(|e| e.to_string())?;
        written += 1;
    }

    zip.start_file("environment.txt", options)
        .map_err(|e| e.to_string())?;
    zip.write_all(environment_summary(&app, server_url.as_deref()).as_bytes())
        .map_err(|e| e.to_string())?;

    zip.finish().map_err(|e| e.to_string())?;

    let size_bytes = fs::metadata(&archive_path)
        .map_err(|e| e.to_string())?
        .len();
    info!(
        "[DIAG] exported {written} log file(s), {size_bytes} bytes -> {}",
        archive_path.display()
    );

    Ok(DiagnosticsBundle {
        path: archive_path.to_string_lossy().to_string(),
        size_bytes,
        file_count: written,
    })
}

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

    #[test]
    fn parses_every_level_name_case_insensitively() {
        assert_eq!(parse_level("debug"), LevelFilter::Debug);
        assert_eq!(parse_level("DEBUG"), LevelFilter::Debug);
        assert_eq!(parse_level("  warn\n"), LevelFilter::Warn);
        assert_eq!(parse_level("error"), LevelFilter::Error);
        assert_eq!(parse_level("trace"), LevelFilter::Trace);
    }

    #[test]
    fn unknown_level_falls_back_to_info_rather_than_failing() {
        // This is read at startup from a file on disk. A corrupt value must not
        // stop the app launching.
        assert_eq!(parse_level("banana"), LevelFilter::Info);
        assert_eq!(parse_level(""), LevelFilter::Info);
    }

    #[test]
    fn level_names_round_trip() {
        for name in ["error", "warn", "info", "debug", "trace"] {
            assert_eq!(level_name(parse_level(name)), name);
        }
    }

    #[test]
    fn stored_level_is_none_when_never_set() {
        let dir = std::env::temp_dir().join("jellytau-diag-test-empty");
        let _ = fs::create_dir_all(&dir);
        let _ = fs::remove_file(dir.join(LEVEL_FILE));
        assert!(stored_level(&dir).is_none());
    }

    #[test]
    fn stored_level_reads_back_what_was_written() {
        let dir = std::env::temp_dir().join("jellytau-diag-test-roundtrip");
        fs::create_dir_all(&dir).unwrap();
        fs::write(dir.join(LEVEL_FILE), "debug").unwrap();
        assert_eq!(stored_level(&dir), Some(LevelFilter::Debug));
        let _ = fs::remove_file(dir.join(LEVEL_FILE));
    }

    #[test]
    fn log_files_ignores_non_log_files() {
        let dir = std::env::temp_dir().join("jellytau-diag-test-listing");
        fs::create_dir_all(&dir).unwrap();
        fs::write(dir.join("jellytau.log"), "x").unwrap();
        fs::write(dir.join("notes.md"), "x").unwrap();
        fs::write(dir.join("jellytau.zip"), "x").unwrap();

        let found = log_files(&dir);
        let names: Vec<String> = found
            .iter()
            .filter_map(|p| p.file_name()?.to_str().map(String::from))
            .collect();

        assert!(names.contains(&"jellytau.log".to_string()));
        // The export archive itself lives elsewhere, but never re-zip a zip.
        assert!(!names.contains(&"jellytau.zip".to_string()));
        assert!(!names.contains(&"notes.md".to_string()));

        let _ = fs::remove_dir_all(&dir);
    }
}