//! The quorum of an article (ADR 0013).
//!
//! Yvv, 2026-11-02: « C suit le cran, mais c'est une proposition par défaut, variable
//! modifiable par l'auteur initial du texte » — « L'auteur, avant le 1er vote ». Each
//! level has its quorum (`documents.quorums`); an article judged on another one holds
//! it in `units.quorum`, set here by the author of its first version (an administrator
//! for a text of the seed, `trustin_access::sets_quorum`), and only while no vote
//! exists on it (`voted_units`). From 2 to W; from 1 in the test group
//! (`ld_engine::inertia::quorum_bounds`). Each change is journaled (`quorum_changes`).
//! An article's own quorum is not published: `document.json` carries the quorums by level.

use crate::AppState;
use crate::auth::{IdentityRow, User};
use crate::docs::{self, DocState, UnitRow};
use crate::error::{AppError, AppResult};
use crate::util;
use axum::Json;
use axum::extract::{Path, State};
use ld_engine::inertia::quorum_bounds;
use serde::Deserialize;
use serde_json::json;
use sqlx::SqliteConnection;
use std::collections::{HashMap, HashSet};

/// **« Un vote existe »** — the units of a document on which a vote exists: the one
/// place this is asked (ADR 0013; lot V extends it here, nowhere else).
///
/// A vote exists on an article when any version of it (its texts, a removal, a change
/// of its inertia; any revision) holds
/// - a vote that counts (`votes`): a vote of a managed group, a vote proven by the
///   chain, a **simulated** vote (ADR 0012);
/// - a line of a ballot — the buffer of the votes keeps their history (ADR 0012) —
///   of the chain or of the simulation: **an intention still pending** (signed, not yet
///   read on the chain: Yvv, 2026-11-03), or a ballot proven, **whatever became of its
///   line**: the voice that counts, a vote overtaken by a more recent one, a *for* set
///   aside by an objection, **a withdrawal** (`none`). A vote withdrawn on the chain or
///   in simulation, before any adoption, thus still says that someone voted. A ballot
///   the wallet never signed (let go at once), never seen on the chain in time, or
///   refused by the chain, is no vote;
/// - an adoption: a version that entered into force by the vote keeps that trace once
///   its votes are withdrawn.
///
/// Two limits, known. In a managed group there is no buffer: a vote of the server
/// withdrawn before any adoption leaves no row (`votes` keeps the last choice only),
/// and from then on no vote exists (ADR 0013). The act « supprime » that ends the
/// simulation (`simulation::discard`) takes the simulated ballots away with their
/// trace: an article voted in simulation only has no vote any more, unless an adoption
/// that holds on the proven votes stays.
pub async fn voted_units(conn: &mut SqliteConnection, doc_id: &str) -> sqlx::Result<HashSet<String>> {
    let ids: Vec<String> = sqlx::query_scalar(
        "SELECT p.unit_id FROM votes v
           JOIN proposals p ON p.id = v.proposal_id JOIN units u ON u.id = p.unit_id
          WHERE u.doc_id = ?1
         UNION
         -- Every ballot of the buffer, chain or simulated, pending or proven: its history.
         SELECT p.unit_id FROM ballot_lines l
           JOIN ballots b ON b.id = l.ballot_id
           JOIN proposals p ON p.id = l.proposal_id JOIN units u ON u.id = p.unit_id
          WHERE u.doc_id = ?1 AND b.status IN ('pending', 'confirmed')
         UNION
         SELECT a.unit_id FROM adoptions a WHERE a.doc_id = ?1",
    )
    .bind(doc_id)
    .fetch_all(&mut *conn)
    .await?;
    Ok(ids.into_iter().collect())
}

/// Does a vote exist on this unit (`voted_units`)?
pub async fn a_vote_exists(state: &AppState, unit_id: &str) -> AppResult<bool> {
    let doc_id = doc_of_unit(state, unit_id).await?;
    let mut conn = state.db.acquire().await?;
    Ok(voted_units(&mut conn, &doc_id).await?.contains(unit_id))
}

async fn doc_of_unit(state: &AppState, unit_id: &str) -> AppResult<String> {
    sqlx::query_scalar("SELECT doc_id FROM units WHERE id = ?")
        .bind(unit_id)
        .fetch_optional(&state.db)
        .await?
        .ok_or(AppError::NotFound)
}

/// The author of each unit's first version (`None`: a text of the seed, without author).
/// A first version is a text — of an article or a module —, never a removal or a change
/// of inertia, whatever became of it since.
pub async fn first_authors(state: &AppState, doc_id: &str) -> AppResult<HashMap<String, Option<String>>> {
    let rows: Vec<(String, Option<String>)> = sqlx::query_as(
        "SELECT p.unit_id, p.author_id FROM proposals p JOIN units u ON u.id = p.unit_id
          WHERE u.doc_id = ? AND p.kind NOT IN ('remove', 'inertia') ORDER BY p.created_at, p.rowid",
    )
    .bind(doc_id)
    .fetch_all(&state.db)
    .await?;
    let mut out = HashMap::new();
    for (unit, author) in rows {
        out.entry(unit).or_insert(author);
    }
    Ok(out)
}

/// What a person may do with the quorums of a document, read once for its view.
pub struct Rights {
    first_authors: HashMap<String, Option<String>>,
    voted: HashSet<String>,
}

impl Rights {
    pub async fn of(state: &AppState, doc_id: &str) -> AppResult<Self> {
        let first_authors = first_authors(state, doc_id).await?;
        let mut conn = state.db.acquire().await?;
        let voted = voted_units(&mut conn, doc_id).await?;
        Ok(Self { first_authors, voted })
    }

    fn first_author(&self, unit: &UnitRow) -> Option<&str> {
        self.first_authors.get(&unit.id).and_then(|a| a.as_deref())
    }

    /// May `user` set the quorum of `unit` now (`trustin_access::sets_quorum`)?
    pub fn sets(&self, user: &IdentityRow, unit: &UnitRow) -> bool {
        trustin_access::sets_quorum(&user.to_identity(), self.first_author(unit), self.voted.contains(&unit.id))
    }
}

/// The quorum of a unit, as its view says it: its own (`null`: its level's), its level's,
/// and whether `user` may set it.
pub fn unit_json(st: &DocState, rights: &Rights, user: &IdentityRow, unit: &UnitRow) -> serde_json::Value {
    json!({
        "quorum": unit.own_quorum(), "quorumDefault": st.quorum_default(unit), "canSetQuorum": rights.sets(user, unit),
    })
}

#[derive(Deserialize)]
pub struct QuorumBody {
    /// A whole number of voters; `null`: back to the quorum of its level.
    quorum: Option<i64>,
}

/// `PUT /units/{id}/quorum`, body `{ "quorum": n | null }`.
pub async fn set(
    State(state): State<AppState>,
    User(user): User,
    Path(unit_id): Path<String>,
    Json(b): Json<QuorumBody>,
) -> AppResult<Json<serde_json::Value>> {
    let doc_id = doc_of_unit(&state, &unit_id).await?;
    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)?;
    let authors = first_authors(&state, &doc_id).await?;
    let first = authors.get(&unit.id).and_then(|a| a.as_deref());
    let identity = user.to_identity();
    if !trustin_access::sets_quorum(&identity, first, false) {
        return Err(AppError::Forbidden);
    }
    let (lowest, highest) = quorum_bounds(st.electorate, st.group.slug == trustin_access::TEST_GROUP);
    let to = match b.quorum {
        None => None,
        Some(q) if q >= i64::from(lowest) && q <= i64::from(highest) => Some(q),
        Some(_) => return Err(AppError::Invalid("quorum")),
    };
    let mut tx = state.db.begin().await?;
    // Asked within the writing transaction: a vote that arrives first wins.
    let voted = voted_units(&mut tx, &doc_id).await?.contains(&unit.id);
    if !trustin_access::sets_quorum(&identity, first, voted) {
        return Err(AppError::Conflict("voted"));
    }
    if unit.quorum != to {
        let now = util::now();
        sqlx::query("UPDATE units SET quorum = ? WHERE id = ?").bind(to).bind(&unit.id).execute(&mut *tx).await?;
        sqlx::query(
            "INSERT INTO quorum_changes (unit_id, doc_id, from_quorum, to_quorum, identity_id, at) VALUES (?, ?, ?, ?, ?, ?)",
        )
        .bind(&unit.id)
        .bind(&doc_id)
        .bind(unit.quorum)
        .bind(to)
        .bind(&user.id)
        .bind(&now)
        .execute(&mut *tx)
        .await?;
        tracing::info!(doc = %doc_id, unit = %unit.code, from = ?unit.quorum, to = ?to, by = %user.id, "quorum set");
    }
    tx.commit().await?;
    Ok(Json(json!({ "quorum": to, "quorumDefault": st.quorum_default(unit), "canSetQuorum": true })))
}