//! Modules — what a document decides besides its articles (ADR 0009).
//!
//! Yvv, 2026-10-30: « En fin de section, il y a un "module" qui permet de
//! changer l'ordre des "articles". Lui-même à (2) » ; « Le titre du doc à (4) »
//! — and, asked whether the title of an article is voted apart: « Non, titre et
//! texte ensemble ». So two modules, each a unit of its own kind:
//!
//! - the **title of the document** (`title`, level 4): its version in force is
//!   the title in the source language (`doc_title`);
//! - the **order of the articles of each section** (`order`, level 2): its
//!   version in force is the order the section reads in now (`order`).
//!
//! A module is voted like an article — unfolded, in the basket, on the Ğ1
//! chain — because its versions are proposals like any other: the same
//! threshold, the same margin over the version in force, the same seed a
//! minima at the start. What differs is only what entering into force does.
//!
//! A new document gets its modules from the seed (`modules` in the seed file);
//! an existing one, once, from what it holds (`module_amend`). Both go through
//! `create`, which reads the document as it is and touches no article and no
//! vote.

use crate::docs::{DocState, ProposalRow, UnitRow};
use crate::error::{AppError, AppResult};
use crate::seed::SeedModules;
use crate::util;
use crate::{doc_title, order};
use ld_engine::inertia::InertiaLevel;
use sqlx::SqliteConnection;

/// The code of the title module of a document.
pub const TITLE_CODE: &str = "titre";

/// The code of the order module of a section.
pub fn order_code(section: &str) -> String {
    format!("ordre.{section}")
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ModuleKind {
    Title,
    Order,
}

impl ModuleKind {
    /// `units.kind`; an article is no module.
    pub fn parse(raw: &str) -> Option<Self> {
        match raw {
            "title" => Some(Self::Title),
            "order" => Some(Self::Order),
            _ => None,
        }
    }

    pub fn as_str(self) -> &'static str {
        match self {
            Self::Title => "title",
            Self::Order => "order",
        }
    }
}

/// The levels a document's modules start at; `None`: no such module.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct Levels {
    pub title: Option<InertiaLevel>,
    pub order: Option<InertiaLevel>,
}

impl From<&SeedModules> for Levels {
    fn from(m: &SeedModules) -> Self {
        Self { title: m.title.as_ref().map(|t| t.inertia), order: m.order.as_ref().map(|o| o.inertia) }
    }
}

/// A version of a module, written directly in force (a seed a minima) or open.
pub(crate) struct NewVersion<'a> {
    pub unit_id: &'a str,
    pub kind: ModuleKind,
    pub title: &'a str,
    pub body: &'a str,
    pub author: Option<&'a str>,
    pub in_force: bool,
    pub now: &'a str,
}

pub(crate) async fn insert_version(conn: &mut SqliteConnection, v: NewVersion<'_>) -> sqlx::Result<String> {
    let id = util::id();
    let (status, origin) = if v.in_force { ("in_force", "seed") } else { ("open", "member") };
    sqlx::query(
        "INSERT INTO proposals (id, unit_id, kind, title, body, status, origin, label, author_id, revision,
           created_at, updated_at, submitted_at)
         VALUES (?, ?, ?, ?, ?, ?, ?, NULL, ?, 1, ?, ?, ?)",
    )
    .bind(&id)
    .bind(v.unit_id)
    .bind(v.kind.as_str())
    .bind(v.title)
    .bind(v.body)
    .bind(status)
    .bind(origin)
    .bind(v.author)
    .bind(v.now)
    .bind(v.now)
    .bind(v.now)
    .execute(&mut *conn)
    .await?;
    sqlx::query(
        "INSERT INTO revisions (proposal_id, revision, kind, title, body, author_id, created_at)
         VALUES (?, 1, 'initial', ?, ?, ?, ?)",
    )
    .bind(&id)
    .bind(v.title)
    .bind(v.body)
    .bind(v.author)
    .bind(v.now)
    .execute(&mut *conn)
    .await?;
    if v.in_force {
        sqlx::query("UPDATE units SET in_force_id = ? WHERE id = ?")
            .bind(&id)
            .bind(v.unit_id)
            .execute(&mut *conn)
            .await?;
    }
    Ok(id)
}

async fn insert_unit(
    conn: &mut SqliteConnection,
    doc_id: &str,
    kind: ModuleKind,
    code: &str,
    section: Option<&str>,
    level: InertiaLevel,
    now: &str,
) -> sqlx::Result<String> {
    let id = util::id();
    // Its place is not among the articles: the reader puts each module where it belongs.
    sqlx::query(
        "INSERT INTO units (id, doc_id, code, section, position, inertia, in_force_id, created_at, kind)
         VALUES (?, ?, ?, ?, 0, ?, NULL, ?, ?)",
    )
    .bind(&id)
    .bind(doc_id)
    .bind(code)
    .bind(section)
    .bind(level.as_db())
    .bind(now)
    .bind(kind.as_str())
    .execute(&mut *conn)
    .await?;
    Ok(id)
}

/// Creates the modules of a document from what it holds now — its title, and
/// the order each of its sections reads in — each in force as a seed a minima.
/// No article, no vote is touched. Returns the codes created.
pub async fn create(conn: &mut SqliteConnection, doc_id: &str, levels: Levels, now: &str) -> sqlx::Result<Vec<String>> {
    let mut created = Vec::new();
    if let Some(level) = levels.title {
        let (raw, src): (String, String) = sqlx::query_as("SELECT title, source_lang FROM documents WHERE id = ?")
            .bind(doc_id)
            .fetch_one(&mut *conn)
            .await?;
        let titles = util::parse_lang(&raw);
        let title = titles.get(&src).cloned().unwrap_or_default();
        let unit = insert_unit(conn, doc_id, ModuleKind::Title, TITLE_CODE, None, level, now).await?;
        let pid = insert_version(
            conn,
            NewVersion {
                unit_id: &unit,
                kind: ModuleKind::Title,
                title: &title,
                body: "",
                author: None,
                in_force: true,
                now,
            },
        )
        .await?;
        doc_title::seed_translations(conn, &pid, &title, &titles, &src, now).await?;
        created.push(TITLE_CODE.to_owned());
    }
    if let Some(level) = levels.order {
        for (section, members) in order::sections_now(conn, doc_id).await? {
            let code = order_code(&section);
            let unit = insert_unit(conn, doc_id, ModuleKind::Order, &code, Some(&section), level, now).await?;
            let body = ld_engine::order::canonical(&members);
            insert_version(
                conn,
                NewVersion {
                    unit_id: &unit,
                    kind: ModuleKind::Order,
                    title: &code,
                    body: &body,
                    author: None,
                    in_force: true,
                    now,
                },
            )
            .await?;
            created.push(code);
        }
    }
    Ok(created)
}

/// What entering into force does, besides the version taking its place: the
/// order of a section moves its articles, the title of a document becomes its
/// title. Returns the kind kept in `adoptions` (`text` for an article).
pub async fn on_entry(
    conn: &mut SqliteConnection,
    st: &DocState,
    unit: &UnitRow,
    p: &ProposalRow,
) -> AppResult<&'static str> {
    match st.module_of(&unit.id) {
        None => Ok("text"),
        Some(ModuleKind::Order) => {
            order::enter(conn, st, unit, p).await?;
            Ok("order")
        }
        Some(ModuleKind::Title) => {
            doc_title::enter(conn, &st.doc.id, unit, p).await?;
            Ok("title")
        }
    }
}

/// The generic writing of a version stops at a module: one proposes a module
/// through its own door (`order::propose`, `doc_title::propose`).
pub fn require_article(st: &DocState, unit_id: &str) -> AppResult<()> {
    if st.module_of(unit_id).is_some() { Err(AppError::Invalid("module")) } else { Ok(()) }
}

/// An order is never corrected nor translated: another order is another proposal.
pub fn require_text(p: &ProposalRow) -> AppResult<()> {
    if p.kind == ModuleKind::Order.as_str() { Err(AppError::Conflict("order_fixed")) } else { Ok(()) }
}