//! Author persistence. Same plain-function style as the other repos.
//!
//! Names are stored with the casing of the first submission; lookups go
//! through the case-insensitive unique index on `lower(name)` so
//! "Kentaro Miura" and "kentaro miura" share one row.

use std::collections::BTreeMap;

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

use crate::domain::author::{Author, AuthorRef, AuthorWithCount};
use crate::domain::manga::Manga;
use crate::error::{AppError, AppResult};

/// Insert-or-find by name. Returns the canonical row whether or not
/// this call created it. The `ON CONFLICT … DO UPDATE` no-op is what
/// makes `RETURNING` come back even on the existing-row path.
pub async fn upsert_by_name<'e, E: PgExecutor<'e>>(
    executor: E,
    name: &str,
) -> AppResult<Author> {
    let trimmed = name.trim();
    if trimmed.is_empty() {
        return Err(AppError::ValidationFailed {
            message: "author name cannot be empty".into(),
            details: serde_json::json!({ "authors": "non-empty names required" }),
        });
    }
    let row = sqlx::query_as::<_, Author>(
        r#"
        INSERT INTO authors (name)
        VALUES ($1)
        ON CONFLICT (lower(name)) DO UPDATE SET name = authors.name
        RETURNING id, name, created_at
        "#,
    )
    .bind(trimmed)
    .fetch_one(executor)
    .await?;
    Ok(row)
}

pub async fn find_by_id(pool: &PgPool, id: Uuid) -> AppResult<Author> {
    sqlx::query_as::<_, Author>(
        "SELECT id, name, created_at FROM authors WHERE id = $1",
    )
    .bind(id)
    .fetch_optional(pool)
    .await?
    .ok_or(AppError::NotFound)
}

pub async fn find_with_count(pool: &PgPool, id: Uuid) -> AppResult<AuthorWithCount> {
    sqlx::query_as::<_, AuthorWithCount>(
        r#"
        SELECT a.id,
               a.name,
               a.created_at,
               (SELECT count(*) FROM manga_authors ma WHERE ma.author_id = a.id) AS manga_count
          FROM authors a
         WHERE a.id = $1
        "#,
    )
    .bind(id)
    .fetch_optional(pool)
    .await?
    .ok_or(AppError::NotFound)
}

/// Autocomplete-friendly: substring + trigram match on `name`, ordered
/// most-similar first when a search term is present.
pub async fn list(
    pool: &PgPool,
    search: Option<&str>,
    limit: i64,
    offset: i64,
) -> AppResult<Vec<Author>> {
    let rows = sqlx::query_as::<_, Author>(
        r#"
        SELECT id, name, created_at
          FROM authors
         WHERE $1::text IS NULL
            OR name ILIKE '%' || $1 || '%'
            OR name % $1
         ORDER BY CASE WHEN $1::text IS NULL THEN 0 ELSE similarity(name, $1) END DESC,
                  lower(name) ASC
         LIMIT $2 OFFSET $3
        "#,
    )
    .bind(search)
    .bind(limit)
    .bind(offset)
    .fetch_all(pool)
    .await?;
    Ok(rows)
}

/// Atomically replace the set of authors on a manga. Caller passes a
/// `&mut PgConnection` (`&mut *tx` works) so the delete+upserts run in
/// one transaction with whatever called us.
///
/// Note: `crawler::repo::sync_authors` does a similar replace with the
/// same semantics on names. The duplication is intentional — handler
/// callers want the `Vec<AuthorRef>` for the API response; the
/// crawler doesn't need it and stays inside its own transaction.
pub async fn set_for_manga(
    conn: &mut PgConnection,
    manga_id: Uuid,
    names: &[String],
) -> AppResult<Vec<AuthorRef>> {
    sqlx::query("DELETE FROM manga_authors WHERE manga_id = $1")
        .bind(manga_id)
        .execute(&mut *conn)
        .await?;

    let mut refs = Vec::with_capacity(names.len());
    for (position, name) in names.iter().enumerate() {
        let author = upsert_by_name(&mut *conn, name).await?;
        sqlx::query(
            "INSERT INTO manga_authors (manga_id, author_id, position) VALUES ($1, $2, $3)
             ON CONFLICT (manga_id, author_id) DO NOTHING",
        )
        .bind(manga_id)
        .bind(author.id)
        .bind(position as i32)
        .execute(&mut *conn)
        .await?;
        refs.push(AuthorRef { id: author.id, name: author.name });
    }
    Ok(refs)
}

pub async fn list_for_manga(pool: &PgPool, manga_id: Uuid) -> AppResult<Vec<AuthorRef>> {
    let rows = sqlx::query_as::<_, AuthorRef>(
        r#"
        SELECT a.id, a.name
          FROM manga_authors ma
          JOIN authors a ON a.id = ma.author_id
         WHERE ma.manga_id = $1
         ORDER BY ma.position, lower(a.name)
        "#,
    )
    .bind(manga_id)
    .fetch_all(pool)
    .await?;
    Ok(rows)
}

/// Batch-load authors for a list of manga ids and group by manga. Used
/// by the list endpoint to avoid N+1 round-trips.
pub async fn load_for_mangas(
    pool: &PgPool,
    manga_ids: &[Uuid],
) -> AppResult<BTreeMap<Uuid, Vec<AuthorRef>>> {
    if manga_ids.is_empty() {
        return Ok(BTreeMap::new());
    }
    let rows: Vec<(Uuid, Uuid, String)> = sqlx::query_as(
        r#"
        SELECT ma.manga_id, a.id, a.name
          FROM manga_authors ma
          JOIN authors a ON a.id = ma.author_id
         WHERE ma.manga_id = ANY($1)
         ORDER BY ma.manga_id, ma.position, lower(a.name)
        "#,
    )
    .bind(manga_ids)
    .fetch_all(pool)
    .await?;
    let mut grouped: BTreeMap<Uuid, Vec<AuthorRef>> = BTreeMap::new();
    for (manga_id, author_id, name) in rows {
        grouped
            .entry(manga_id)
            .or_default()
            .push(AuthorRef { id: author_id, name });
    }
    Ok(grouped)
}

pub async fn list_mangas_for_author(
    pool: &PgPool,
    author_id: Uuid,
    limit: i64,
    offset: i64,
) -> AppResult<(Vec<Manga>, i64)> {
    let rows = sqlx::query_as::<_, Manga>(
        r#"
        SELECT m.id, m.title, m.status, m.alt_titles, m.description,
               m.cover_image_path, m.created_at, m.updated_at
          FROM manga_authors ma
          JOIN mangas m ON m.id = ma.manga_id
         WHERE ma.author_id = $1
         ORDER BY m.created_at DESC, m.id
         LIMIT $2 OFFSET $3
        "#,
    )
    .bind(author_id)
    .bind(limit)
    .bind(offset)
    .fetch_all(pool)
    .await?;
    let (total,): (i64,) = sqlx::query_as(
        "SELECT count(*) FROM manga_authors WHERE author_id = $1",
    )
    .bind(author_id)
    .fetch_one(pool)
    .await?;
    Ok((rows, total))
}
