//! Manga persistence.
//!
//! Plain async functions over `&PgPool` rather than a repository struct —
//! each function is easy to test in isolation with `#[sqlx::test]`, and
//! handlers depend only on `sqlx::PgPool`, not on a trait object. Swap to
//! a trait + impl if a second backend ever becomes necessary.

use serde::Deserialize;
use sqlx::{PgConnection, PgExecutor, PgPool};
use uuid::Uuid;

use crate::domain::manga::{Manga, MangaCard, MangaDetail};
use crate::error::{AppError, AppResult};
use crate::repo;

/// Status values mirror the CHECK constraint in 0009. Centralized so
/// the API layer can validate uploads against the same vocabulary.
pub const STATUSES: &[&str] = &["ongoing", "completed"];
pub const DEFAULT_STATUS: &str = "ongoing";

#[derive(Debug, Clone, Copy, Default, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ListSort {
    /// Newest first (default).
    #[default]
    Recent,
    /// A→Z by title (case-insensitive).
    Title,
}

#[derive(Debug, Clone, Default)]
pub struct ListQuery {
    pub search: Option<String>,
    pub status: Option<String>,
    pub author_ids: Vec<Uuid>,
    pub genre_ids: Vec<Uuid>,
    pub tag_ids: Vec<Uuid>,
    pub limit: i64,
    pub offset: i64,
    pub sort: ListSort,
}

const SELECT_COLS: &str =
    "id, title, status, alt_titles, description, cover_image_path, created_at, updated_at";

/// Shared WHERE used by both the rows and the count queries. Filters
/// are AND across facets: every supplied author_id (or genre, or tag)
/// must be attached to the manga for it to match. Empty arrays mean
/// "no filter" because `NOT EXISTS` over an empty unnest is vacuously
/// true.
const FILTER_WHERE: &str = r#"
    ($1::text IS NULL
     OR title ILIKE '%' || $1 || '%'
     OR title % $1
     OR EXISTS (
            SELECT 1 FROM manga_authors ma
              JOIN authors a ON a.id = ma.author_id
             WHERE ma.manga_id = mangas.id
               AND (a.name ILIKE '%' || $1 || '%' OR a.name % $1)
        )
    )
    AND ($2::text IS NULL OR status = $2)
    AND NOT EXISTS (
        SELECT 1 FROM unnest($3::uuid[]) AS req(id)
         WHERE NOT EXISTS (
                SELECT 1 FROM manga_authors ma
                 WHERE ma.manga_id = mangas.id AND ma.author_id = req.id
             )
    )
    AND NOT EXISTS (
        SELECT 1 FROM unnest($4::uuid[]) AS req(id)
         WHERE NOT EXISTS (
                SELECT 1 FROM manga_genres mg
                 WHERE mg.manga_id = mangas.id AND mg.genre_id = req.id
             )
    )
    AND NOT EXISTS (
        SELECT 1 FROM unnest($5::uuid[]) AS req(id)
         WHERE NOT EXISTS (
                SELECT 1 FROM manga_tags mt
                 WHERE mt.manga_id = mangas.id AND mt.tag_id = req.id
             )
    )
"#;

/// Returns the page of mangas matching `query` plus the unfiltered total
/// count for the same filter. The trigram GIN indexes (see 0005_search.sql
/// and 0009_manga_metadata.sql) keep both queries cheap as the library
/// grows.
pub async fn list(pool: &PgPool, query: &ListQuery) -> AppResult<(Vec<Manga>, i64)> {
    // `order_by` is interpolated from a hard-coded enum, never from request
    // input, so this is not a SQL injection seam.
    let order_by = match query.sort {
        ListSort::Recent => "created_at DESC, id",
        ListSort::Title => "lower(title) ASC, id",
    };

    let search = query.search.as_deref();
    let status = query.status.as_deref();

    let list_sql = format!(
        r#"
        SELECT {SELECT_COLS}
        FROM mangas
        WHERE {FILTER_WHERE}
        ORDER BY {order_by}
        LIMIT $6 OFFSET $7
        "#
    );

    let rows = sqlx::query_as::<_, Manga>(&list_sql)
        .bind(search)
        .bind(status)
        .bind(&query.author_ids)
        .bind(&query.genre_ids)
        .bind(&query.tag_ids)
        .bind(query.limit)
        .bind(query.offset)
        .fetch_all(pool)
        .await?;

    let count_sql = format!(
        r#"
        SELECT count(*) FROM mangas
        WHERE {FILTER_WHERE}
        "#
    );
    let (total,): (i64,) = sqlx::query_as(&count_sql)
        .bind(search)
        .bind(status)
        .bind(&query.author_ids)
        .bind(&query.genre_ids)
        .bind(&query.tag_ids)
        .fetch_one(pool)
        .await?;

    Ok((rows, total))
}

/// Same filter as `list`, but wraps each row with its authors + genres
/// in a single batched round-trip. Tags are intentionally not loaded
/// here — see `MangaCard` in the domain layer.
pub async fn list_cards(
    pool: &PgPool,
    query: &ListQuery,
) -> AppResult<(Vec<MangaCard>, i64)> {
    let (rows, total) = list(pool, query).await?;
    let ids: Vec<Uuid> = rows.iter().map(|m| m.id).collect();
    let mut authors = repo::author::load_for_mangas(pool, &ids).await?;
    let mut genres = repo::genre::load_for_mangas(pool, &ids).await?;
    let cards = rows
        .into_iter()
        .map(|manga| MangaCard {
            authors: authors.remove(&manga.id).unwrap_or_default(),
            genres: genres.remove(&manga.id).unwrap_or_default(),
            manga,
        })
        .collect();
    Ok((cards, total))
}

pub async fn get(pool: &PgPool, id: Uuid) -> AppResult<Manga> {
    sqlx::query_as::<_, Manga>(&format!(
        "SELECT {SELECT_COLS} FROM mangas WHERE id = $1"
    ))
    .bind(id)
    .fetch_optional(pool)
    .await?
    .ok_or(AppError::NotFound)
}

pub async fn get_detail(pool: &PgPool, id: Uuid) -> AppResult<MangaDetail> {
    let manga = get(pool, id).await?;
    let authors = repo::author::list_for_manga(pool, id).await?;
    let genres = repo::genre::list_for_manga(pool, id).await?;
    let tags = repo::tag::list_for_manga(pool, id).await?;
    Ok(MangaDetail { manga, authors, genres, tags })
}

/// Insert just the manga row. Relations (authors, genres) are written
/// by the caller via `repo::author::set_for_manga` etc. in the same
/// transaction. `status` is taken as a validated string — the handler
/// is responsible for defaulting/validating it.
///
/// `uploaded_by` records who created the manga and feeds the per-user
/// upload history. `None` means "historical / no associated user" —
/// historic rows from before the uploader columns were added carry
/// NULL.
pub async fn create<'e, E: PgExecutor<'e>>(
    executor: E,
    title: &str,
    status: &str,
    description: Option<&str>,
    alt_titles: &[String],
    uploaded_by: Option<Uuid>,
) -> AppResult<Manga> {
    let row = sqlx::query_as::<_, Manga>(&format!(
        r#"
        INSERT INTO mangas (title, status, description, alt_titles, uploaded_by)
        VALUES ($1, $2, $3, $4, $5)
        RETURNING {SELECT_COLS}
        "#
    ))
    .bind(title)
    .bind(status)
    .bind(description)
    .bind(alt_titles)
    .bind(uploaded_by)
    .fetch_one(executor)
    .await?;
    Ok(row)
}

/// Patch the inline columns. Each `Option` argument leaves the field
/// untouched when `None`. `description` uses two binds — a `provided`
/// boolean and the new value — so callers can distinguish "leave
/// alone" from "set to NULL" (both look the same in a plain
/// `Option<&str>` because serde collapses missing and explicit-null).
pub async fn update_basics(
    conn: &mut PgConnection,
    id: Uuid,
    title: Option<&str>,
    status: Option<&str>,
    description_provided: bool,
    description: Option<&str>,
    alt_titles: Option<&[String]>,
) -> AppResult<Manga> {
    let row = sqlx::query_as::<_, Manga>(&format!(
        r#"
        UPDATE mangas
           SET title       = COALESCE($2, title),
               status      = COALESCE($3, status),
               description = CASE WHEN $4::boolean THEN $5 ELSE description END,
               alt_titles  = COALESCE($6, alt_titles),
               updated_at  = now()
         WHERE id = $1
        RETURNING {SELECT_COLS}
        "#
    ))
    .bind(id)
    .bind(title)
    .bind(status)
    .bind(description_provided)
    .bind(description)
    .bind(alt_titles)
    .fetch_optional(&mut *conn)
    .await?
    .ok_or(AppError::NotFound)?;
    Ok(row)
}

pub async fn set_cover_image_path<'e, E: PgExecutor<'e>>(
    executor: E,
    id: Uuid,
    key: &str,
) -> AppResult<()> {
    sqlx::query("UPDATE mangas SET cover_image_path = $1, updated_at = now() WHERE id = $2")
        .bind(key)
        .bind(id)
        .execute(executor)
        .await?;
    Ok(())
}

pub async fn clear_cover_image_path<'e, E: PgExecutor<'e>>(
    executor: E,
    id: Uuid,
) -> AppResult<()> {
    sqlx::query("UPDATE mangas SET cover_image_path = NULL, updated_at = now() WHERE id = $1")
        .bind(id)
        .execute(executor)
        .await?;
    Ok(())
}

pub async fn exists(pool: &PgPool, id: Uuid) -> AppResult<bool> {
    let (exists,): (bool,) =
        sqlx::query_as("SELECT EXISTS(SELECT 1 FROM mangas WHERE id = $1)")
            .bind(id)
            .fetch_one(pool)
            .await?;
    Ok(exists)
}