//! File I/O and directory traversal for ticket storage.
//!
//! Tickets are stored in `.nbd/tickets/` relative to the project root.
//! Each ticket is a single file named `{id}.{ext}`, where the extension
//! depends on the [`FileFormat`]:
//!
//! | Format | Extension | Description |
//! |---|---|---|
//! | [`FileFormat::Json`] | `.json` | Pretty-printed JSON (default) |
//! | [`FileFormat::Markdown`] | `.md` | Markdown body with TOML frontmatter |
//! | [`FileFormat::Toml`] | `.toml` | TOML |
//! | [`FileFormat::Jsonb`] | `.jsonb` | CBOR binary |
//!
//! The root is discovered by walking up from the current working directory
//! until a `.nbd/` directory is found, mirroring how `git` locates `.git/`.

use std::path::{Path, PathBuf};

use serde::{Deserialize, Serialize};
use tokio::fs;

use crate::filter::TicketFilter;
use crate::ticket::{Status, Ticket, TicketType};

/// Convenience alias for fallible operations in this module.
///
/// The error type is a heap-allocated trait object so that both `io::Error`
/// and `serde_json::Error` (and any other `std::error::Error` implementor)
/// can be returned with `?` without additional wrapping.
pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;

/// Convert a string message into a boxed error, with an unambiguous type.
fn msg_err(s: String) -> Box<dyn std::error::Error + Send + Sync> {
    s.into()
}

// ── FileFormat ────────────────────────────────────────────────────────────────

/// The on-disk serialisation format for a ticket file.
///
/// The format is determined by the file extension when reading, and must be
/// supplied explicitly when writing a new file. `Json` is the default.
///
/// # Examples
///
/// ```
/// use nbd::store::FileFormat;
/// assert_eq!(FileFormat::Json.extension(), "json");
/// assert_eq!(FileFormat::Markdown.extension(), "md");
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum FileFormat {
    /// Pretty-printed JSON (`.json`). The original and default format.
    #[default]
    Json,
    /// Markdown file with TOML frontmatter (`.md`).
    ///
    /// The ticket body is stored as the file content after the closing `+++`
    /// delimiter; all other fields live in the TOML frontmatter block.
    Markdown,
    /// TOML (`.toml`). All ticket fields except `id` are stored as TOML.
    Toml,
    /// CBOR binary encoding (`.jsonb`). Compact binary alternative to JSON.
    Jsonb,
}

impl FileFormat {
    /// The file extension associated with this format (without a leading dot).
    pub fn extension(self) -> &'static str {
        match self {
            FileFormat::Json => "json",
            FileFormat::Markdown => "md",
            FileFormat::Toml => "toml",
            FileFormat::Jsonb => "jsonb",
        }
    }

    /// Parse a [`FileFormat`] from a user-supplied string.
    ///
    /// Accepts `"json"`, `"md"`, `"toml"`, and `"jsonb"`.
    /// Returns `None` for unrecognised values.
    pub fn from_str(s: &str) -> Option<Self> {
        match s {
            "json" => Some(FileFormat::Json),
            "md" => Some(FileFormat::Markdown),
            "toml" => Some(FileFormat::Toml),
            "jsonb" => Some(FileFormat::Jsonb),
            _ => None,
        }
    }
}

impl std::fmt::Display for FileFormat {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.extension())
    }
}

/// File extensions recognised as ticket files, tried in this order on reads.
const KNOWN_EXTENSIONS: &[&str] = &["json", "md", "toml", "jsonb"];

/// Detect the [`FileFormat`] from a file path's extension.
///
/// Falls back to [`FileFormat::Json`] for absent or unrecognised extensions.
pub fn detect_format(path: &Path) -> FileFormat {
    match path.extension().and_then(|e| e.to_str()) {
        Some("json") => FileFormat::Json,
        Some("md") => FileFormat::Markdown,
        Some("toml") => FileFormat::Toml,
        Some("jsonb") => FileFormat::Jsonb,
        _ => FileFormat::Json,
    }
}

// ── Markdown frontmatter helper ───────────────────────────────────────────────

/// Ticket metadata stored in TOML frontmatter for `.md` files.
///
/// The `body` field is intentionally absent here: in the markdown format the
/// body is the file content that follows the closing `+++` delimiter.
#[derive(Serialize, Deserialize)]
struct MarkdownFrontmatter {
    title: String,
    priority: u8,
    status: Status,
    ticket_type: TicketType,
    dependencies: Vec<String>,
}

// ── Serialisation helpers ─────────────────────────────────────────────────────

/// Serialise `ticket` to a pretty-printed JSON string.
fn serialize_json(ticket: &Ticket) -> Result<String> {
    Ok(serde_json::to_string_pretty(ticket)?)
}

/// Serialise `ticket` to a TOML string.
fn serialize_toml(ticket: &Ticket) -> Result<String> {
    Ok(toml::to_string(ticket)?)
}

/// Serialise `ticket` to a markdown document with TOML frontmatter.
///
/// Format:
/// ```text
/// +++
/// title = "..."
/// priority = 5
/// ...
/// +++
/// Body content here.
/// ```
fn serialize_markdown(ticket: &Ticket) -> Result<String> {
    let fm = MarkdownFrontmatter {
        title: ticket.title.clone(),
        priority: ticket.priority,
        status: ticket.status.clone(),
        ticket_type: ticket.ticket_type.clone(),
        dependencies: ticket.dependencies.clone(),
    };
    let toml_str = toml::to_string(&fm)?;
    Ok(format!("+++\n{toml_str}+++\n{}", ticket.body))
}

/// Serialise `ticket` to CBOR binary.
fn serialize_jsonb(ticket: &Ticket) -> Result<Vec<u8>> {
    let mut buf = Vec::new();
    ciborium::ser::into_writer(ticket, &mut buf)
        .map_err(|e| msg_err(format!("CBOR serialization error: {e}")))?;
    Ok(buf)
}

// ── Deserialisation helpers ───────────────────────────────────────────────────

/// Deserialise a ticket from JSON bytes.
fn deserialize_json(bytes: &[u8]) -> Result<Ticket> {
    Ok(serde_json::from_slice(bytes)?)
}

/// Deserialise a ticket from TOML bytes.
fn deserialize_toml(bytes: &[u8]) -> Result<Ticket> {
    let s = std::str::from_utf8(bytes)?;
    Ok(toml::from_str(s)?)
}

/// Deserialise a ticket from a markdown document with TOML frontmatter.
///
/// The document must begin with `+++\n`, contain a closing `\n+++\n`, and
/// have TOML key-value pairs between the two delimiters. Everything after the
/// closing delimiter becomes the ticket body.
fn deserialize_markdown(bytes: &[u8]) -> Result<Ticket> {
    let content = std::str::from_utf8(bytes)?;

    let after_open = content
        .strip_prefix("+++\n")
        .ok_or("markdown ticket must start with '+++\\n'")?;

    let (fm_str, body) = after_open
        .split_once("\n+++\n")
        .ok_or("markdown ticket is missing a closing '+++' delimiter")?;

    let fm: MarkdownFrontmatter = toml::from_str(fm_str)?;

    Ok(Ticket {
        id: String::new(),
        title: fm.title,
        body: body.to_string(),
        priority: fm.priority,
        status: fm.status,
        ticket_type: fm.ticket_type,
        dependencies: fm.dependencies,
    })
}

/// Deserialise a ticket from CBOR binary bytes.
fn deserialize_jsonb(bytes: &[u8]) -> Result<Ticket> {
    ciborium::de::from_reader(bytes)
        .map_err(|e| msg_err(format!("CBOR deserialization error: {e}")))
}

/// Deserialise `bytes` using the detected `format`.
fn deserialize_by_format(bytes: &[u8], format: FileFormat) -> Result<Ticket> {
    match format {
        FileFormat::Json => deserialize_json(bytes),
        FileFormat::Markdown => deserialize_markdown(bytes),
        FileFormat::Toml => deserialize_toml(bytes),
        FileFormat::Jsonb => deserialize_jsonb(bytes),
    }
}

// ── Directory helpers ─────────────────────────────────────────────────────────

/// Walk upward from `start` until a directory containing `.nbd/` is found.
///
/// Returns the first ancestor path (inclusive of `start`) that contains a
/// `.nbd/` subdirectory, or an error if the filesystem root is reached without
/// finding one.
///
/// This is the low-level, testable variant. Most callers should use
/// [`find_nbd_root`], which starts from the current working directory.
///
/// # Errors
///
/// Returns an error if no `.nbd/` directory exists in `start` or any of its
/// ancestors.
pub fn find_nbd_root_from(start: &Path) -> Result<PathBuf> {
    let mut dir = start;
    loop {
        if dir.join(".nbd").is_dir() {
            return Ok(dir.to_path_buf());
        }
        match dir.parent() {
            Some(parent) => dir = parent,
            None => break,
        }
    }
    Err(
        "could not find .nbd/ directory; create `.nbd/tickets/` in your project root to initialise"
            .into(),
    )
}

/// Walk upward from the current working directory until a `.nbd/` directory is
/// found.
///
/// This is the primary entry point used by all CLI commands. Internally
/// delegates to [`find_nbd_root_from`].
///
/// # Errors
///
/// Returns an error if the current working directory cannot be determined, or
/// if no `.nbd/` directory exists in it or any of its ancestors.
pub fn find_nbd_root() -> Result<PathBuf> {
    let cwd = std::env::current_dir()?;
    find_nbd_root_from(&cwd)
}

/// Return the path to the tickets directory within a project root.
///
/// This is a pure path computation — it does not check whether the directory
/// exists.
pub fn tickets_dir(root: &Path) -> PathBuf {
    root.join(".nbd").join("tickets")
}

/// Create `.nbd/tickets/` under `root` if it does not already exist.
///
/// All intermediate directories (including `.nbd/`) are created as needed.
/// This should only be called by the `create` command; other commands can
/// assume the directory already exists.
///
/// # Errors
///
/// Propagates any I/O error returned by the filesystem.
pub async fn ensure_tickets_dir(root: &Path) -> Result<()> {
    let dir = tickets_dir(root);
    fs::create_dir_all(dir).await?;
    Ok(())
}

// ── Path helpers ──────────────────────────────────────────────────────────────

/// Return the path to a specific ticket file for the given `format`.
///
/// This is a pure path computation — it does not check whether the file
/// exists.
pub fn ticket_path(root: &Path, id: &str, format: FileFormat) -> PathBuf {
    tickets_dir(root).join(format!("{id}.{}", format.extension()))
}

/// Find and return the actual on-disk path of a ticket, trying each known
/// extension in order.
///
/// # Errors
///
/// Returns an error if no file with a known extension exists for `id`.
pub async fn find_ticket_path(root: &Path, id: &str) -> Result<PathBuf> {
    let dir = tickets_dir(root);
    for ext in KNOWN_EXTENSIONS {
        let path = dir.join(format!("{id}.{ext}"));
        if path.is_file() {
            return Ok(path);
        }
    }
    Err(format!("ticket '{id}' not found").into())
}

// ── CRUD operations ───────────────────────────────────────────────────────────

/// Serialise `ticket` and write it to `.nbd/tickets/{id}.{ext}` using
/// `format` to determine both the extension and the serialisation.
///
/// Overwrites any existing file at the same path. The tickets directory must
/// already exist; call [`ensure_tickets_dir`] before calling this for a new
/// ticket.
///
/// # Errors
///
/// Returns an error if serialisation fails or if the file cannot be written.
pub async fn write_ticket(root: &Path, ticket: &Ticket, format: FileFormat) -> Result<()> {
    let path = ticket_path(root, &ticket.id, format);
    match format {
        FileFormat::Json => {
            let json = serialize_json(ticket)?;
            fs::write(path, json).await?;
        }
        FileFormat::Markdown => {
            let content = serialize_markdown(ticket)?;
            fs::write(path, content).await?;
        }
        FileFormat::Toml => {
            let content = serialize_toml(ticket)?;
            fs::write(path, content).await?;
        }
        FileFormat::Jsonb => {
            let bytes = serialize_jsonb(ticket)?;
            fs::write(path, bytes).await?;
        }
    }
    Ok(())
}

/// Resolve a full 6-character ticket ID from an exact ID or a unique prefix.
///
/// If `id_or_prefix` is already an exact match for a ticket on disk (in any
/// supported format), it is returned unchanged. Otherwise all ticket filenames
/// whose stem starts with `id_or_prefix` are collected and:
///
/// - **0 matches** → error: `"no ticket found matching '{prefix}'"`
/// - **1 match**  → the full 6-character ID is returned
/// - **2+ matches** → error: `"ambiguous prefix '{prefix}' matches: {id1}, {id2}, ..."`
///
/// # Errors
///
/// Returns an error if no match is found, the prefix is ambiguous, or the
/// tickets directory cannot be read.
pub async fn resolve_id(root: &Path, id_or_prefix: &str) -> Result<String> {
    let dir = tickets_dir(root);

    // Fast path: if exactly 6 chars, check all known extensions.
    if id_or_prefix.len() == 6 {
        for ext in KNOWN_EXTENSIONS {
            if dir.join(format!("{id_or_prefix}.{ext}")).is_file() {
                return Ok(id_or_prefix.to_string());
            }
        }
    }

    // Scan directory for prefix matches across all known formats.
    if !dir.is_dir() {
        return Err(format!("no ticket found matching '{id_or_prefix}'").into());
    }

    let mut entries = fs::read_dir(&dir).await?;
    let mut matches: Vec<String> = Vec::new();

    while let Some(entry) = entries.next_entry().await? {
        // Construct a std::path::PathBuf so it's compatible with Path helpers.
        let path: PathBuf = dir.join(entry.file_name());
        let ext = path
            .extension()
            .and_then(|e| e.to_str())
            .unwrap_or_default();
        if !KNOWN_EXTENSIONS.contains(&ext) {
            continue;
        }
        if let Some(stem) = path.file_stem().and_then(|s| s.to_str()) {
            if stem.starts_with(id_or_prefix) && !matches.contains(&stem.to_string()) {
                matches.push(stem.to_string());
            }
        }
    }

    match matches.len() {
        0 => Err(format!("no ticket found matching '{id_or_prefix}'").into()),
        1 => Ok(matches.remove(0)),
        _ => {
            matches.sort();
            Err(format!(
                "ambiguous prefix '{id_or_prefix}' matches: {}",
                matches.join(", ")
            )
            .into())
        }
    }
}

/// Read and deserialise the ticket with the given `id` from disk.
///
/// Extensions are tried in the order defined by [`KNOWN_EXTENSIONS`]. The
/// first matching file is used. The `id` is not stored inside the file; it
/// is injected from the `id` parameter after deserialisation, making the
/// filename stem the authoritative source of truth.
///
/// # Errors
///
/// Returns a descriptive error message if no file is found for `id`.
/// Propagates any other I/O or deserialisation error unchanged.
pub async fn read_ticket(root: &Path, id: &str) -> Result<Ticket> {
    let dir = tickets_dir(root);
    for ext in KNOWN_EXTENSIONS {
        let path = dir.join(format!("{id}.{ext}"));
        match fs::read(&path).await {
            Ok(bytes) => {
                let format = detect_format(&path);
                let mut ticket = deserialize_by_format(&bytes, format)?;
                ticket.id = id.to_string();
                return Ok(ticket);
            }
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => continue,
            Err(e) => return Err(e.into()),
        }
    }
    Err(format!("ticket '{id}' not found").into())
}

/// Report produced by [`migrate_tickets`].
///
/// Summarises how many ticket files were updated, were already current,
/// were skipped by the filter, or could not be parsed.
#[derive(Debug)]
pub struct MigrateReport {
    /// Number of files that were re-serialised (had stale content).
    pub updated: usize,
    /// Number of files that were already in the current schema format.
    pub already_current: usize,
    /// Number of files excluded by the caller-supplied [`TicketFilter`].
    pub skipped: usize,
    /// Files that could not be deserialised. Each entry is `(filename, error)`.
    pub errors: Vec<(String, String)>,
}

/// Re-serialise every ticket file through the current serde schema.
///
/// For each ticket file in `.nbd/tickets/` (any supported format):
/// - Deserialise into [`Ticket`], injecting the `id` from the filename stem.
/// - If the ticket does not match `filter`, count it as skipped and continue.
/// - Re-serialise in the same format.
/// - If the bytes differ, write the new content (unless `dry_run` is `true`).
/// - If the bytes are identical, count the file as already current.
/// - If deserialisation fails, record the error and leave the file untouched.
///
/// When `dry_run` is `true`, no files are written; the report describes what
/// *would* have changed. The function always returns `Ok` — individual file
/// errors are collected in [`MigrateReport::errors`] rather than aborting early.
///
/// # Errors
///
/// Returns an error only if the tickets directory itself cannot be read.
pub async fn migrate_tickets(
    root: &Path,
    dry_run: bool,
    filter: &TicketFilter,
) -> Result<MigrateReport> {
    let dir = tickets_dir(root);
    let mut report = MigrateReport {
        updated: 0,
        already_current: 0,
        skipped: 0,
        errors: Vec::new(),
    };

    if !dir.is_dir() {
        return Ok(report);
    }

    let mut entries = fs::read_dir(&dir).await?;
    while let Some(entry) = entries.next_entry().await? {
        // Construct a std::path::PathBuf so it's compatible with Path helpers.
        let path: PathBuf = dir.join(entry.file_name());

        let ext = path
            .extension()
            .and_then(|e| e.to_str())
            .unwrap_or_default();
        if !KNOWN_EXTENSIONS.contains(&ext) {
            continue;
        }

        let filename = path
            .file_name()
            .and_then(|n| n.to_str())
            .unwrap_or("")
            .to_string();
        let stem = path
            .file_stem()
            .and_then(|s| s.to_str())
            .unwrap_or("")
            .to_string();

        let raw = match fs::read(&path).await {
            Ok(b) => b,
            Err(e) => {
                report.errors.push((filename, e.to_string()));
                continue;
            }
        };

        let format = detect_format(&path);
        let mut ticket: Ticket = match deserialize_by_format(&raw, format) {
            Ok(t) => t,
            Err(e) => {
                report.errors.push((filename, e.to_string()));
                continue;
            }
        };
        ticket.id = stem;

        // Apply caller-supplied filter; skip non-matching tickets.
        if !filter.matches(&ticket) {
            report.skipped += 1;
            continue;
        }

        // Re-serialise in the same format to normalise the schema.
        let new_bytes: Vec<u8> = match format {
            FileFormat::Json => match serialize_json(&ticket) {
                Ok(s) => s.into_bytes(),
                Err(e) => {
                    report.errors.push((filename, e.to_string()));
                    continue;
                }
            },
            FileFormat::Markdown => match serialize_markdown(&ticket) {
                Ok(s) => s.into_bytes(),
                Err(e) => {
                    report.errors.push((filename, e.to_string()));
                    continue;
                }
            },
            FileFormat::Toml => match serialize_toml(&ticket) {
                Ok(s) => s.into_bytes(),
                Err(e) => {
                    report.errors.push((filename, e.to_string()));
                    continue;
                }
            },
            FileFormat::Jsonb => match serialize_jsonb(&ticket) {
                Ok(b) => b,
                Err(e) => {
                    report.errors.push((filename, e.to_string()));
                    continue;
                }
            },
        };

        if raw == new_bytes {
            report.already_current += 1;
        } else if dry_run {
            report.updated += 1;
        } else {
            if let Err(e) = fs::write(&path, &new_bytes).await {
                report.errors.push((filename, e.to_string()));
                continue;
            }
            report.updated += 1;
        }
    }

    Ok(report)
}

/// Read every ticket file in the tickets directory and return them sorted by
/// priority descending (highest priority first).
///
/// All supported file formats (`.json`, `.md`, `.toml`, `.jsonb`) are scanned.
/// If the tickets directory does not exist, an empty `Vec` is returned.
///
/// # Errors
///
/// Returns an error if the directory listing fails, if any ticket file cannot
/// be read, or if any ticket's content cannot be deserialised.
pub async fn list_tickets(root: &Path) -> Result<Vec<Ticket>> {
    let dir = tickets_dir(root);

    if !dir.is_dir() {
        return Ok(Vec::new());
    }

    let mut entries = fs::read_dir(&dir).await?;
    let mut tickets = Vec::new();
    // Guard against the same logical ticket appearing in multiple formats.
    let mut seen_ids: std::collections::HashSet<String> = std::collections::HashSet::new();

    while let Some(entry) = entries.next_entry().await? {
        // Construct a std::path::PathBuf so it's compatible with Path helpers.
        let path: PathBuf = dir.join(entry.file_name());
        let ext = path
            .extension()
            .and_then(|e| e.to_str())
            .unwrap_or_default();
        if !KNOWN_EXTENSIONS.contains(&ext) {
            continue;
        }
        let stem = path
            .file_stem()
            .and_then(|s| s.to_str())
            .ok_or("ticket filename has no valid stem")?
            .to_string();
        if !seen_ids.insert(stem.clone()) {
            // Same ID already loaded from a different-extension file; skip.
            continue;
        }
        let bytes = fs::read(&path).await?;
        let format = detect_format(&path);
        let mut ticket = deserialize_by_format(&bytes, format)?;
        ticket.id = stem;
        tickets.push(ticket);
    }

    // Highest priority value first; ties preserve filesystem order.
    tickets.sort_by(|a, b| b.priority.cmp(&a.priority));
    Ok(tickets)
}

// ── Turso (libsql) cache ──────────────────────────────────────────────────────

/// Open (or create) the libsql cache database at `.nbd/cache.db`.
///
/// Runs the schema migration on every open so the table exists when needed.
/// The returned [`libsql::Connection`] is ready for queries.
///
/// # Errors
///
/// Returns an error if the database cannot be opened or the migration fails.
async fn open_cache(root: &Path) -> Result<libsql::Connection> {
    let db_path = root.join(".nbd").join("cache.db");
    let db = libsql::Builder::new_local(db_path)
        .build()
        .await
        .map_err(|e| msg_err(format!("libsql open error: {e}")))?;
    let conn = db
        .connect()
        .map_err(|e| msg_err(format!("libsql connect error: {e}")))?;
    conn.execute(
        "CREATE TABLE IF NOT EXISTS tickets (
            id    TEXT    PRIMARY KEY,
            json  TEXT    NOT NULL,
            mtime INTEGER NOT NULL
        )",
        (),
    )
    .await
    .map_err(|e| msg_err(format!("libsql migrate error: {e}")))?;
    Ok(conn)
}

/// Like [`list_tickets`] but uses a libsql cache in `.nbd/cache.db` to skip
/// re-reading files whose modification time has not changed.
///
/// ## Cache strategy
///
/// 1. Scan `.nbd/tickets/` for files and their mtimes.
/// 2. For each file: if the cache row exists and the mtime matches, deserialise
///    the cached JSON; otherwise read the file, parse it, and upsert the cache.
/// 3. Delete rows for IDs that no longer exist on disk.
/// 4. Return tickets sorted by priority descending.
///
/// Falls back to [`list_tickets`] if the cache cannot be opened or any cache
/// operation fails, so the caller always gets a result.
///
/// # Errors
///
/// Only returns an error if [`list_tickets`] itself fails (the fallback path).
pub async fn list_tickets_cached(root: &Path) -> Result<Vec<Ticket>> {
    match list_tickets_cached_inner(root).await {
        Ok(tickets) => Ok(tickets),
        Err(_) => list_tickets(root).await,
    }
}

/// Inner implementation of the cached list; errors cause a fallback to the
/// uncached path in [`list_tickets_cached`].
async fn list_tickets_cached_inner(root: &Path) -> Result<Vec<Ticket>> {
    let dir = tickets_dir(root);

    if !dir.is_dir() {
        return Ok(Vec::new());
    }

    let conn = open_cache(root).await?;

    // Scan the directory, collecting (id, path, mtime_secs) for each ticket file.
    let mut on_disk: Vec<(String, PathBuf, i64)> = Vec::new();
    let mut read_dir = fs::read_dir(&dir).await?;
    while let Some(entry) = read_dir.next_entry().await? {
        let path: PathBuf = dir.join(entry.file_name());
        let ext = path
            .extension()
            .and_then(|e| e.to_str())
            .unwrap_or_default();
        if !KNOWN_EXTENSIONS.contains(&ext) {
            continue;
        }
        let stem = match path.file_stem().and_then(|s| s.to_str()) {
            Some(s) => s.to_string(),
            None => continue,
        };
        let meta = fs::metadata(&path).await?;
        let mtime = meta
            .modified()
            .ok()
            .and_then(|t| {
                t.duration_since(std::time::UNIX_EPOCH)
                    .ok()
                    .map(|d| d.as_millis() as i64)
            })
            .unwrap_or(0);
        on_disk.push((stem, path, mtime));
    }

    // Deduplicate: keep only the first occurrence of each ID (same order as list_tickets).
    let mut seen_ids: std::collections::HashSet<String> = std::collections::HashSet::new();
    on_disk.retain(|(id, _, _)| seen_ids.insert(id.clone()));

    let disk_ids: std::collections::HashSet<String> =
        on_disk.iter().map(|(id, _, _)| id.clone()).collect();

    let mut tickets: Vec<Ticket> = Vec::with_capacity(on_disk.len());

    for (id, path, mtime) in &on_disk {
        // Query the cache for this id.
        let cached_json: Option<String> = {
            let mut rows = conn
                .query(
                    "SELECT json FROM tickets WHERE id = ?1 AND mtime = ?2",
                    libsql::params![id.as_str(), *mtime],
                )
                .await
                .map_err(|e| msg_err(format!("cache query error: {e}")))?;
            if let Some(row) = rows
                .next()
                .await
                .map_err(|e| msg_err(format!("cache row error: {e}")))?
            {
                Some(
                    row.get::<String>(0)
                        .map_err(|e| msg_err(format!("cache column error: {e}")))?,
                )
            } else {
                None
            }
        };

        let mut ticket = if let Some(json) = cached_json {
            serde_json::from_str::<Ticket>(&json)
                .map_err(|e| msg_err(format!("cache deserialise error: {e}")))?
        } else {
            // Cache miss: read file and upsert.
            let bytes = fs::read(path).await?;
            let format = detect_format(path);
            let t = deserialize_by_format(&bytes, format)?;
            // Store normalised JSON in the cache.
            let json = serde_json::to_string(&t)?;
            conn.execute(
                "INSERT OR REPLACE INTO tickets (id, json, mtime) VALUES (?1, ?2, ?3)",
                libsql::params![id.as_str(), json.as_str(), *mtime],
            )
            .await
            .map_err(|e| msg_err(format!("cache upsert error: {e}")))?;
            t
        };
        ticket.id = id.clone();
        tickets.push(ticket);
    }

    // Remove stale rows for IDs no longer on disk.
    // We fetch all cached IDs and delete anything not in `disk_ids`.
    let mut rows = conn
        .query("SELECT id FROM tickets", ())
        .await
        .map_err(|e| msg_err(format!("cache scan error: {e}")))?;
    let mut stale: Vec<String> = Vec::new();
    while let Some(row) = rows
        .next()
        .await
        .map_err(|e| msg_err(format!("cache row error: {e}")))?
    {
        let cached_id: String = row
            .get::<String>(0)
            .map_err(|e| msg_err(format!("cache column error: {e}")))?;
        if !disk_ids.contains(&cached_id) {
            stale.push(cached_id);
        }
    }
    for id in stale {
        conn.execute(
            "DELETE FROM tickets WHERE id = ?1",
            libsql::params![id.as_str()],
        )
        .await
        .map_err(|e| msg_err(format!("cache delete error: {e}")))?;
    }

    tickets.sort_by(|a, b| b.priority.cmp(&a.priority));
    Ok(tickets)
}