//! TRACES: FR-EXP-10 | FR-EXP-6 | FR-CAT-7
//! Albums: named export folders, and which photographs went into each.
//!
//! An album is where finished pictures go — a folder of JPEGs somebody else
//! looks at — as opposed to a collection, which is a set of originals the
//! photographer works on. The folder holds only the exported files. What the
//! catalog adds is the link back: each export is recorded against the image
//! it was rendered from, so opening an album in the library shows the RAWs
//! behind its JPEGs, and re-exporting after an edit is one selection away.
//!
//! # Where the folder is, and why that is two tables
//!
//! An album's folder is either on the library's server or on this device.
//!
//! A **server folder** is one path on the account, the same from every device
//! signed in to it, so it lives on the album row and syncs with it.
//!
//! A **local folder** — a filesystem path on a desktop, a Storage Access
//! Framework tree on Android — means nothing on any other device. It lives in
//! `album_folders`, which the merge never reads and the upload snapshot drops
//! ([`crate::sync::snapshot_for_upload`]). An album made on the desktop with a
//! local folder therefore reaches the tablet as an album with no folder there
//! yet, which is true, and which the tablet can fix by choosing one.
//!
//! # Created on first use, not by a migration
//!
//! A new schema version makes every older build refuse this catalog's
//! snapshot at sync (`crate::sync::remote_is_mergeable`), so the tablet would
//! stop merging collections, keywords and people until it was updated — for
//! a feature it does not have. The tables are created by [`ensure_tables`]
//! instead, the way `dedup_probes` is; an older build that meets them ignores
//! them, and its merge keeps working.
//!
//! # Sync
//!
//! Albums merge by uuid and revision with tombstones, and their exports as a
//! set union keyed on the image's server file id — the rules
//! [`crate::merge`] applies to collections, for the same reasons.

use rusqlite::{Connection, OptionalExtension};

use dr_types::ImageId;

use crate::error::CatalogError;

/// Identifies an album within one catalog. Local, like every integer id here;
/// the uuid is what crosses devices.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct AlbumId(pub u64);

/// Where an album's files go.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Place {
    /// A folder on the library's server, relative to the account root, with no
    /// leading slash. The same on every device.
    Server(String),
    /// A folder on this device: a filesystem path, or on Android a SAF tree
    /// URI. Never synced.
    Local(String),
}

/// One album, as the sidebar and the export sheet show it.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Album {
    pub id: AlbumId,
    pub uuid: String,
    pub name: String,
    /// Where exports go from this device, or `None` for an album whose folder
    /// is local to another device and has not been chosen here.
    pub place: Option<Place>,
    /// Distinct photographs exported into it — what the grid shows when the
    /// album is opened.
    pub sources: usize,
}

/// Create the album tables if this catalog does not have them yet.
///
/// Cheap when they exist: `IF NOT EXISTS` is answered from the schema, and
/// every function below calls this first so no caller has to remember to.
pub fn ensure_tables(conn: &Connection) -> Result<(), CatalogError> {
    conn.execute_batch(
        "CREATE TABLE IF NOT EXISTS albums (
             id          INTEGER PRIMARY KEY,
             -- The merge identity; the integer id is local.
             uuid        TEXT    NOT NULL UNIQUE,
             name        TEXT    NOT NULL,
             -- A folder on the server, relative to the account root. NULL for
             -- an album whose folder is local to some device.
             server_path TEXT,
             created     INTEGER NOT NULL,
             revision    INTEGER NOT NULL DEFAULT 1,
             modified    INTEGER NOT NULL,
             deleted     INTEGER NOT NULL DEFAULT 0
         );
         -- One row per file written into an album. Keyed on the file, not the
         -- image: a photograph exported twice — two crops, or once before an
         -- edit and once after — is two files in the folder and two rows here.
         CREATE TABLE IF NOT EXISTS album_exports (
             album_id    INTEGER NOT NULL REFERENCES albums(id) ON DELETE CASCADE,
             file_name   TEXT    NOT NULL,
             image_id    INTEGER NOT NULL REFERENCES images(id) ON DELETE CASCADE,
             exported_at INTEGER NOT NULL,
             PRIMARY KEY (album_id, file_name)
         );
         CREATE INDEX IF NOT EXISTS album_exports_image ON album_exports(image_id);
         -- This device's folder for an album. Never merged, never uploaded.
         CREATE TABLE IF NOT EXISTS album_folders (
             album_id INTEGER PRIMARY KEY REFERENCES albums(id) ON DELETE CASCADE,
             folder   TEXT    NOT NULL
         );",
    )?;
    Ok(())
}

/// Make an album.
///
/// The name is trimmed and must not be empty; two albums may share one, as
/// two collections may, because the uuid is the identity and refusing a
/// duplicate name here would refuse it on one device and not another.
pub fn create(conn: &Connection, name: &str, place: &Place) -> Result<AlbumId, CatalogError> {
    ensure_tables(conn)?;
    let name = name.trim();
    if name.is_empty() {
        return Err(CatalogError::EmptyName);
    }
    let now = now_secs();
    let tx = conn.unchecked_transaction()?;
    tx.execute(
        "INSERT INTO albums(uuid, name, server_path, created, revision, modified)
         VALUES (?1, ?2, ?3, ?4, 1, ?4)",
        rusqlite::params![
            crate::collections::new_uuid(),
            name,
            server_path(place),
            now
        ],
    )?;
    let id = AlbumId(tx.last_insert_rowid() as u64);
    if let Place::Local(folder) = place {
        tx.execute(
            "INSERT INTO album_folders(album_id, folder) VALUES (?1, ?2)",
            rusqlite::params![id.0 as i64, folder],
        )?;
    }
    tx.commit()?;
    Ok(id)
}

/// Rename an album. The folder keeps its name: the album is what the
/// photographer calls it, the folder is what is already out there.
pub fn rename(conn: &Connection, id: AlbumId, name: &str) -> Result<(), CatalogError> {
    ensure_tables(conn)?;
    let name = name.trim();
    if name.is_empty() {
        return Err(CatalogError::EmptyName);
    }
    let n = conn.execute(
        "UPDATE albums SET name = ?2, revision = revision + 1, modified = ?3
          WHERE id = ?1 AND deleted = 0",
        rusqlite::params![id.0 as i64, name, now_secs()],
    )?;
    if n == 0 {
        return Err(CatalogError::NoSuchAlbum(id.0));
    }
    Ok(())
}

/// Point an album at a different folder, from this device.
///
/// A server folder replaces the synced path, and bumps the revision so the
/// move reaches every device. A local folder is recorded for this device
/// only; it also clears a server path, because an album goes to one place and
/// the photographer has just said which.
pub fn set_place(conn: &Connection, id: AlbumId, place: &Place) -> Result<(), CatalogError> {
    ensure_tables(conn)?;
    let tx = conn.unchecked_transaction()?;
    let n = tx.execute(
        "UPDATE albums SET server_path = ?2, revision = revision + 1, modified = ?3
          WHERE id = ?1 AND deleted = 0",
        rusqlite::params![id.0 as i64, server_path(place), now_secs()],
    )?;
    if n == 0 {
        return Err(CatalogError::NoSuchAlbum(id.0));
    }
    match place {
        Place::Local(folder) => tx.execute(
            "INSERT INTO album_folders(album_id, folder) VALUES (?1, ?2)
             ON CONFLICT(album_id) DO UPDATE SET folder = excluded.folder",
            rusqlite::params![id.0 as i64, folder],
        )?,
        Place::Server(_) => tx.execute(
            "DELETE FROM album_folders WHERE album_id = ?1",
            [id.0 as i64],
        )?,
    };
    tx.commit()?;
    Ok(())
}

/// Delete an album, leaving a tombstone. The files in its folder are not
/// touched: they are finished work somebody may already have been sent a
/// link to, and the album was only ever this catalog's note of them.
pub fn delete(conn: &Connection, id: AlbumId) -> Result<(), CatalogError> {
    ensure_tables(conn)?;
    let tx = conn.unchecked_transaction()?;
    let n = tx.execute(
        "UPDATE albums SET deleted = 1, revision = revision + 1, modified = ?2
          WHERE id = ?1 AND deleted = 0",
        rusqlite::params![id.0 as i64, now_secs()],
    )?;
    if n == 0 {
        return Err(CatalogError::NoSuchAlbum(id.0));
    }
    tx.execute(
        "DELETE FROM album_exports WHERE album_id = ?1",
        [id.0 as i64],
    )?;
    tx.execute(
        "DELETE FROM album_folders WHERE album_id = ?1",
        [id.0 as i64],
    )?;
    tx.commit()?;
    Ok(())
}

/// Every live album, by name, with how many photographs each holds.
///
/// One statement: the counts are aggregated from `album_exports` first and
/// joined to the (few) albums, not counted per row.
pub fn list(conn: &Connection) -> Result<Vec<Album>, CatalogError> {
    ensure_tables(conn)?;
    let mut stmt = conn.prepare(
        "SELECT a.id, a.uuid, a.name, a.server_path, f.folder, coalesce(e.n, 0)
           FROM albums a
           LEFT JOIN album_folders f ON f.album_id = a.id
           LEFT JOIN (SELECT album_id, count(DISTINCT image_id) AS n
                        FROM album_exports GROUP BY album_id) e
                  ON e.album_id = a.id
          WHERE a.deleted = 0
          ORDER BY a.name COLLATE NOCASE, a.id",
    )?;
    let rows = stmt
        .query_map([], album_from_row)?
        .collect::<Result<Vec<_>, _>>()?;
    Ok(rows)
}

/// One album, or `None` if it is gone.
pub fn get(conn: &Connection, id: AlbumId) -> Result<Option<Album>, CatalogError> {
    ensure_tables(conn)?;
    Ok(conn
        .query_row(
            "SELECT a.id, a.uuid, a.name, a.server_path, f.folder,
                    (SELECT count(DISTINCT image_id) FROM album_exports WHERE album_id = a.id)
               FROM albums a
               LEFT JOIN album_folders f ON f.album_id = a.id
              WHERE a.id = ?1 AND a.deleted = 0",
            [id.0 as i64],
            album_from_row,
        )
        .optional()?)
}

/// The album with this uuid, if this catalog holds it live.
pub fn id_for_uuid(conn: &Connection, uuid: &str) -> Result<Option<AlbumId>, CatalogError> {
    ensure_tables(conn)?;
    Ok(conn
        .query_row(
            "SELECT id FROM albums WHERE uuid = ?1 AND deleted = 0",
            [uuid],
            |r| r.get::<_, i64>(0),
        )
        .optional()?
        .map(|id| AlbumId(id as u64)))
}

/// Record the files one export wrote into an album, and which image each
/// came from. One transaction for the batch, however many files it placed.
///
/// A file name already recorded is re-pointed at the image that wrote it
/// last: an export that overwrote `IMG_0001.jpg` replaced the picture in the
/// folder, and the link must say what is there now.
pub fn record_exports(
    conn: &Connection,
    id: AlbumId,
    files: &[(ImageId, String)],
) -> Result<(), CatalogError> {
    ensure_tables(conn)?;
    if files.is_empty() {
        return Ok(());
    }
    let tx = conn.unchecked_transaction()?;
    let now = now_secs();
    {
        let mut insert = tx.prepare(
            "INSERT INTO album_exports(album_id, file_name, image_id, exported_at)
             VALUES (?1, ?2, ?3, ?4)
             ON CONFLICT(album_id, file_name) DO UPDATE SET
                 image_id = excluded.image_id, exported_at = excluded.exported_at",
        )?;
        for (image, name) in files {
            insert.execute(rusqlite::params![id.0 as i64, name, image.0 as i64, now])?;
        }
    }
    tx.commit()?;
    Ok(())
}

/// Every file name an album records, for an export choosing a name to know
/// what it would land on.
///
/// A server album cannot be asked while the export is queued offline, and
/// the names this app put there are the ones a second export of the same
/// photographs will collide with. One read of the album's rows, not one per
/// candidate name.
pub fn file_names(
    conn: &Connection,
    id: AlbumId,
) -> Result<std::collections::HashSet<String>, CatalogError> {
    ensure_tables(conn)?;
    let mut stmt = conn.prepare("SELECT file_name FROM album_exports WHERE album_id = ?1")?;
    let rows = stmt
        .query_map([id.0 as i64], |r| r.get(0))?
        .collect::<Result<_, _>>()?;
    Ok(rows)
}

/// A file the upload had to give another name: the server held one by the
/// name the export recorded, put there by something this catalog never
/// saw. The album row follows the file to the name it was given.
///
/// By the album's server folder, because that is all an outbox entry knows.
/// `folder` is spelled as [`Place::Server`] spells it, without slashes at
/// either end.
pub fn rename_export(
    conn: &Connection,
    folder: &str,
    from: &str,
    to: &str,
) -> Result<(), CatalogError> {
    ensure_tables(conn)?;
    conn.execute(
        "UPDATE OR REPLACE album_exports SET file_name = ?3
          WHERE file_name = ?2
            AND album_id IN (SELECT id FROM albums WHERE server_path = ?1 AND deleted = 0)",
        rusqlite::params![folder.trim_matches('/'), from, to],
    )?;
    Ok(())
}

/// The photographs behind an album's files, most recently exported first —
/// what the grid shows when the album is opened.
pub fn sources(conn: &Connection, id: AlbumId) -> Result<Vec<ImageId>, CatalogError> {
    ensure_tables(conn)?;
    let mut stmt = conn.prepare(
        "SELECT image_id FROM album_exports
          WHERE album_id = ?1
          GROUP BY image_id
          ORDER BY max(exported_at) DESC, image_id",
    )?;
    let rows = stmt
        .query_map([id.0 as i64], |r| r.get::<_, i64>(0))?
        .map(|r| r.map(|i| ImageId(i as u64)))
        .collect::<Result<Vec<_>, _>>()?;
    Ok(rows)
}

/// The names of the files an image left in an album — the "which JPEG is
/// this" half of the link.
pub fn files_of(
    conn: &Connection,
    id: AlbumId,
    image: ImageId,
) -> Result<Vec<String>, CatalogError> {
    ensure_tables(conn)?;
    let mut stmt = conn.prepare(
        "SELECT file_name FROM album_exports
          WHERE album_id = ?1 AND image_id = ?2
          ORDER BY exported_at DESC, file_name",
    )?;
    let rows = stmt
        .query_map(rusqlite::params![id.0 as i64, image.0 as i64], |r| r.get(0))?
        .collect::<Result<Vec<_>, _>>()?;
    Ok(rows)
}

fn album_from_row(r: &rusqlite::Row<'_>) -> rusqlite::Result<Album> {
    let server: Option<String> = r.get(3)?;
    let local: Option<String> = r.get(4)?;
    Ok(Album {
        id: AlbumId(r.get::<_, i64>(0)? as u64),
        uuid: r.get(1)?,
        name: r.get(2)?,
        // A server path wins: `set_place` clears the local folder when it
        // sets one, so both being present means a merge brought a server
        // path in over a local choice — and the newer revision decided that.
        place: server.map(Place::Server).or(local.map(Place::Local)),
        sources: r.get::<_, i64>(5)? as usize,
    })
}

fn server_path(place: &Place) -> Option<&str> {
    match place {
        Place::Server(p) => Some(p.trim_matches('/')),
        Place::Local(_) => None,
    }
}

fn now_secs() -> i64 {
    std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0)
}

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

    /// A catalog, and the connection to it. The `Catalog` has to outlive the
    /// connection it hands out, so tests hold both.
    fn catalog() -> crate::Catalog {
        let cat = crate::Catalog::in_memory().unwrap();
        cat.connection()
            .execute(
                "INSERT INTO roots(id, kind, label) VALUES (1, 'local', 'lib')",
                [],
            )
            .unwrap();
        cat
    }

    fn image(conn: &Connection, path: &str) -> ImageId {
        conn.execute(
            "INSERT INTO images(root_id, source_ref, added_at) VALUES (1, ?1, 0)",
            [path],
        )
        .unwrap();
        ImageId(conn.last_insert_rowid() as u64)
    }

    #[test]
    fn an_album_lists_with_its_place_and_no_photographs() {
        let cat = catalog();
        let conn = cat.connection();
        let web = create(conn, " Web ", &Place::Server("Shared/Web/".into())).unwrap();
        let print = create(conn, "Print", &Place::Local("/mnt/print".into())).unwrap();

        let all = list(conn).unwrap();
        assert_eq!(all.len(), 2);
        assert_eq!(all[0].id, print, "sorted by name");
        assert_eq!(all[0].place, Some(Place::Local("/mnt/print".into())));
        assert_eq!(all[1].id, web);
        assert_eq!(all[1].name, "Web", "trimmed");
        assert_eq!(all[1].place, Some(Place::Server("Shared/Web".into())));
        assert_eq!(all[1].sources, 0);
    }

    #[test]
    fn an_empty_name_is_refused() {
        let cat = catalog();
        let conn = cat.connection();
        assert!(matches!(
            create(conn, "  ", &Place::Local("/x".into())),
            Err(CatalogError::EmptyName)
        ));
    }

    #[test]
    fn exports_link_files_back_to_their_images() {
        let cat = catalog();
        let conn = cat.connection();
        let album = create(conn, "Web", &Place::Local("/out".into())).unwrap();
        let a = image(conn, "a.cr3");
        let b = image(conn, "b.cr3");

        record_exports(
            conn,
            album,
            &[
                (a, "a.jpg".into()),
                (a, "a (1).jpg".into()),
                (b, "b.jpg".into()),
            ],
        )
        .unwrap();

        let got = get(conn, album).unwrap().unwrap();
        assert_eq!(got.sources, 2, "two photographs, three files");
        let mut s = sources(conn, album).unwrap();
        s.sort();
        assert_eq!(s, vec![a, b]);
        assert_eq!(files_of(conn, album, a).unwrap().len(), 2);
    }

    #[test]
    fn an_overwritten_file_points_at_what_wrote_it_last() {
        let cat = catalog();
        let conn = cat.connection();
        let album = create(conn, "Web", &Place::Local("/out".into())).unwrap();
        let a = image(conn, "a.cr3");
        let b = image(conn, "b.cr3");
        record_exports(conn, album, &[(a, "x.jpg".into())]).unwrap();
        record_exports(conn, album, &[(b, "x.jpg".into())]).unwrap();
        assert_eq!(sources(conn, album).unwrap(), vec![b]);
    }

    #[test]
    fn a_renamed_upload_moves_the_row_of_the_server_album_only() {
        let cat = catalog();
        let conn = cat.connection();
        let web = create(conn, "Web", &Place::Server("Albums/Web".into())).unwrap();
        let other = create(conn, "Other", &Place::Server("Albums/Other".into())).unwrap();
        let a = image(conn, "a.cr3");
        record_exports(conn, web, &[(a, "a.jpg".into())]).unwrap();
        record_exports(conn, other, &[(a, "a.jpg".into())]).unwrap();

        rename_export(conn, "/Albums/Web", "a.jpg", "a-1.jpg").unwrap();

        assert_eq!(
            file_names(conn, web).unwrap(),
            ["a-1.jpg".to_string()].into()
        );
        assert_eq!(
            file_names(conn, other).unwrap(),
            ["a.jpg".to_string()].into()
        );
    }

    #[test]
    fn moving_to_the_server_forgets_the_local_folder() {
        let cat = catalog();
        let conn = cat.connection();
        let album = create(conn, "Web", &Place::Local("/out".into())).unwrap();
        set_place(conn, album, &Place::Server("Web".into())).unwrap();
        assert_eq!(
            get(conn, album).unwrap().unwrap().place,
            Some(Place::Server("Web".into()))
        );
        set_place(conn, album, &Place::Local("/again".into())).unwrap();
        assert_eq!(
            get(conn, album).unwrap().unwrap().place,
            Some(Place::Local("/again".into()))
        );
    }

    #[test]
    fn a_deleted_album_is_gone_and_its_uuid_no_longer_resolves() {
        let cat = catalog();
        let conn = cat.connection();
        let album = create(conn, "Web", &Place::Local("/out".into())).unwrap();
        let uuid = get(conn, album).unwrap().unwrap().uuid;
        let a = image(conn, "a.cr3");
        record_exports(conn, album, &[(a, "a.jpg".into())]).unwrap();

        delete(conn, album).unwrap();
        assert!(list(conn).unwrap().is_empty());
        assert_eq!(id_for_uuid(conn, &uuid).unwrap(), None);
        assert!(matches!(
            rename(conn, album, "Again"),
            Err(CatalogError::NoSuchAlbum(_))
        ));
    }

    #[test]
    fn a_rename_bumps_the_revision_the_merge_compares() {
        let cat = catalog();
        let conn = cat.connection();
        let album = create(conn, "Web", &Place::Local("/out".into())).unwrap();
        rename(conn, album, "Website").unwrap();
        let rev: i64 = conn
            .query_row(
                "SELECT revision FROM albums WHERE id = ?1",
                [album.0 as i64],
                |r| r.get(0),
            )
            .unwrap();
        assert_eq!(rev, 2);
    }
}