//! The title of a document, a module (ADR 0009, level 4).
//!
//! Its version in force is the title in the source language, the one that
//! holds. `documents.title` keeps the title as every list and the publication
//! read it: the source language from the version in force, the other languages
//! from its editorial translations (`sync`).
//!
//! When another title enters into force, the document changes title in the
//! source language. Its translations stay editorial (Yvv, 2026-10-21: the
//! French is voted, the translations are not): the new version takes those of
//! the title it replaces, pinned to that title's text, so they read « à
//! revoir » until a member translates the new one.

use crate::AppState;
use crate::auth::User;
use crate::docs::{self, ProposalRow, UnitRow};
use crate::error::{AppError, AppResult};
use crate::modules::{self, ModuleKind, NewVersion};
use crate::util::{self, LangMap};
use axum::Json;
use axum::extract::{Path, State};
use ld_engine::edit;
use serde::Deserialize;
use serde_json::{Value, json};
use sqlx::SqliteConnection;

/// The longest title, as for an article.
const MAX_TITLE: usize = 120;

/// The translations of the title a document starts with, from its seed or its row.
pub async fn seed_translations(
    conn: &mut SqliteConnection,
    proposal_id: &str,
    title: &str,
    titles: &LangMap,
    src: &str,
    now: &str,
) -> sqlx::Result<()> {
    let hash = util::source_hash(title, "");
    for lang in util::LANGS.iter().filter(|l| **l != src) {
        let Some(t) = titles.get(*lang).filter(|t| !t.trim().is_empty()) else { continue };
        sqlx::query(
            "INSERT INTO translations (proposal_id, lang, title, body, source_hash, origin, updated_by, updated_at)
             VALUES (?, ?, ?, '', ?, 'seed', NULL, ?)",
        )
        .bind(proposal_id)
        .bind(lang)
        .bind(t)
        .bind(&hash)
        .bind(now)
        .execute(&mut *conn)
        .await?;
    }
    Ok(())
}

/// `documents.title` from the title in force and its translations; a language
/// the version in force does not translate keeps the title it had.
pub async fn sync_conn(conn: &mut SqliteConnection, doc_id: &str) -> sqlx::Result<()> {
    let row: Option<(String, String, String, String)> = sqlx::query_as(
        "SELECT p.id, p.title, d.title, d.source_lang FROM units u
           JOIN proposals p ON p.id = u.in_force_id JOIN documents d ON d.id = u.doc_id
          WHERE u.doc_id = ? AND u.kind = 'title'",
    )
    .bind(doc_id)
    .fetch_optional(&mut *conn)
    .await?;
    let Some((pid, title, raw, src)) = row else { return Ok(()) };
    let mut titles = util::parse_lang(&raw);
    titles.insert(src, title);
    let translated: Vec<(String, String)> =
        sqlx::query_as("SELECT lang, title FROM translations WHERE proposal_id = ?")
            .bind(&pid)
            .fetch_all(&mut *conn)
            .await?;
    for (lang, t) in translated {
        titles.insert(lang, t);
    }
    let next = util::lang_json(&titles);
    if next != raw {
        sqlx::query("UPDATE documents SET title = ? WHERE id = ?").bind(&next).bind(doc_id).execute(&mut *conn).await?;
    }
    Ok(())
}

/// After any change to a text in force (a typo, a translation, an entry): the
/// document's title follows its title in force.
pub async fn sync(state: &AppState, doc_id: &str) -> sqlx::Result<()> {
    let mut conn = state.db.acquire().await?;
    sync_conn(&mut conn, doc_id).await
}

/// Another title enters into force: it takes the translations of the one it
/// replaces where it has none — « à revoir », pinned to the former title — and
/// becomes the document's title.
pub async fn enter(conn: &mut SqliteConnection, doc_id: &str, unit: &UnitRow, p: &ProposalRow) -> AppResult<()> {
    if let Some(before) = unit.in_force_id.as_deref().filter(|b| *b != p.id) {
        sqlx::query(
            "INSERT INTO translations (proposal_id, lang, title, body, source_hash, origin, updated_by, updated_at)
             SELECT ?1, t.lang, t.title, t.body, t.source_hash, t.origin, t.updated_by, t.updated_at
               FROM translations t
              WHERE t.proposal_id = ?2
                AND NOT EXISTS (SELECT 1 FROM translations n WHERE n.proposal_id = ?1 AND n.lang = t.lang)",
        )
        .bind(&p.id)
        .bind(before)
        .execute(&mut *conn)
        .await?;
    }
    sync_conn(conn, doc_id).await?;
    tracing::info!(doc = %doc_id, proposal = %p.id, "title of the document in force");
    Ok(())
}

#[derive(Deserialize)]
pub struct TitleBody {
    title: String,
}

/// Propose another title for the document. An open proposal of the same title
/// is given back rather than doubled.
pub async fn propose(
    State(state): State<AppState>,
    User(user): User,
    Path(unit_id): Path<String>,
    Json(b): Json<TitleBody>,
) -> AppResult<Json<Value>> {
    let doc_id: String = sqlx::query_scalar("SELECT doc_id FROM units WHERE id = ?")
        .bind(&unit_id)
        .fetch_optional(&state.db)
        .await?
        .ok_or(AppError::NotFound)?;
    let st = docs::load_state(&state, &doc_id).await?;
    docs::require_open(&state, &user, &st.group).await?;
    let unit = st.units.iter().find(|u| u.id == unit_id).ok_or(AppError::NotFound)?;
    if st.module_of(&unit.id) != Some(ModuleKind::Title) {
        return Err(AppError::Invalid("not_a_title"));
    }
    if edit::has_hidden_controls(&b.title) {
        return Err(AppError::Invalid("hidden_characters"));
    }
    let title = b.title.trim();
    if title.is_empty() || title.chars().count() > MAX_TITLE || title.contains(['\n', '\r']) {
        return Err(AppError::Invalid("title"));
    }
    let in_force = unit.in_force_id.as_deref().and_then(|id| st.proposals.iter().find(|p| p.id == id));
    if in_force.is_some_and(|p| p.title == title) {
        return Err(AppError::Invalid("same_title"));
    }
    if let Some(existing) = st.proposals.iter().find(|p| {
        p.unit_id == unit.id && p.status == "open" && p.kind == ModuleKind::Title.as_str() && p.title == title
    }) {
        return Ok(Json(json!({ "id": existing.id, "existing": true })));
    }
    let now = util::now();
    let mut conn = state.db.acquire().await?;
    let id = modules::insert_version(
        &mut conn,
        NewVersion {
            unit_id: &unit.id,
            kind: ModuleKind::Title,
            title,
            body: "",
            author: Some(&user.id),
            in_force: false,
            now: &now,
        },
    )
    .await?;
    Ok(Json(json!({ "id": id, "existing": false })))
}