//! Inertia amendments — a starting level of the seed raised in an existing base.
//!
//! Yvv, 2026-10-30: « Tu mets par défaut au milieu (3) pour toutes les
//! propositions, (4) pour les 2 engagements structurels » — Unicité du compte
//! (E1) and Réciprocité (E2). New bases get level 4 from the seed. An existing
//! base, where both are in force at the starting level (`standard`, now 3),
//! gets it through an amendment listed here, and **only if no vote ever
//! changed the article's inertia**:
//!
//! - no adoption of a change of inertia on the article (`adoptions`, and the
//!   journal `inertia_changes`);
//! - its level is still the one the amendment raises (the seed's 3).
//!
//! An open proposal to change the inertia does not stop it (orch, 2026-10-30:
//! two such proposals exist in production, I1 → 5 and E1 → 5, at zero votes):
//! it stays open, with its target, and is voted at the article's new level,
//! since a change of inertia inherits it (ADR 0007).
//!
//! Like the seed amendments (`seed_amend`), each document is decided once, at
//! the first start that knows the amendment; the decision is kept in
//! `inertia_amendments` (applied, refused and why, or present) and in the
//! logs. Applied, the level is written in one transaction with a line in
//! `inertia_changes` (the article says so) and, where the document publishes,
//! a row in the publication queue (`document.json` carries the levels).
//!
//! Since 2026-11-02 the seed gives E1 and E2 another starting level: put forward
//! as seed proposals, they start low (ADR 0011, `seed_proposal_amend`). The two
//! amendments of 30/10 are then superseded: decided in production, they decide
//! nothing more, and say so only in the debug logs.

use crate::AppState;
use crate::seed::SeedDoc;
use crate::util;
use ld_engine::inertia::InertiaLevel;
use sqlx::SqliteConnection;

/// One starting level to raise, in every document instantiated from a seed.
pub struct InertiaAmendment {
    /// Stable identifier: each document's decision is kept under it.
    pub id: &'static str,
    /// Slug of the seed document.
    pub doc: &'static str,
    /// Code of the article.
    pub unit: &'static str,
    /// The level it must still hold.
    pub from: u8,
    /// The level it gets: the seed's today, which must say so.
    pub to: u8,
    /// Reason given to the publication queue, and so to the commit of the texts.
    pub reason: &'static str,
    /// The later decision whose level the seed gives instead, if any: this one then
    /// decides nothing more, without an error.
    pub superseded_by: Option<&'static str>,
}

pub const AMENDMENTS: &[InertiaAmendment] = &[
    InertiaAmendment {
        id: "2026-10-30-e1-inertie-4",
        doc: "acte-engagement-certification",
        unit: "E1",
        from: 3,
        to: 4,
        reason: "inertie de départ relevée : E1, 3 → 4",
        superseded_by: Some("2026-11-02-e1-proposition-seed"),
    },
    InertiaAmendment {
        id: "2026-10-30-e2-inertie-4",
        doc: "acte-engagement-certification",
        unit: "E2",
        from: 3,
        to: 4,
        reason: "inertie de départ relevée : E2, 3 → 4",
        superseded_by: Some("2026-11-02-e2-proposition-seed"),
    },
];

/// What the database says of the article.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct Facts {
    /// `units.inertia` as written.
    pub raw: String,
    /// Changes of its inertia that a vote brought into force.
    pub voted_changes: i64,
    /// Open proposals to change its inertia (they stay open; told in the logs).
    pub open_proposals: i64,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Verdict {
    Apply,
    /// The level is already there: nothing to do.
    Present,
    Refuse(&'static str),
}

/// The rule, apart from the database: a vote on the inertia keeps it.
pub fn verdict(facts: Option<&Facts>, a: &InertiaAmendment) -> Verdict {
    let Some(f) = facts else { return Verdict::Refuse("no_article") };
    let Some(level) = InertiaLevel::parse(&f.raw) else { return Verdict::Refuse("level_unreadable") };
    if level.get() == a.to {
        return Verdict::Present;
    }
    if f.voted_changes > 0 {
        Verdict::Refuse("changed_by_vote")
    } else if level.get() != a.from {
        Verdict::Refuse("level_differs")
    } else {
        Verdict::Apply
    }
}

/// A decision taken at this start.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Outcome {
    pub amendment: &'static str,
    pub group: String,
    pub verdict: Verdict,
}

/// Decides every amendment not yet decided, document by document.
pub async fn apply(state: &AppState, seeds: &[SeedDoc], list: &[InertiaAmendment]) -> anyhow::Result<Vec<Outcome>> {
    let mut out = Vec::new();
    for a in list {
        if !seed_says(seeds, a) {
            continue;
        }
        let docs: Vec<(String, String, Option<String>)> =
            sqlx::query_as("SELECT id, group_slug, publish_path FROM documents WHERE slug = ? ORDER BY group_slug")
                .bind(a.doc)
                .fetch_all(&state.db)
                .await?;
        for (doc_id, group, publish_path) in docs {
            let Some((v, open)) = decide(state, a, &doc_id, publish_path.is_some()).await? else { continue };
            match v {
                Verdict::Apply => tracing::info!(
                    amendment = a.id, %group, unit = a.unit, from = a.from, to = a.to, open_inertia_proposals = open,
                    "inertia amendment applied"
                ),
                Verdict::Present => {
                    tracing::info!(amendment = a.id, %group, unit = a.unit, "inertia amendment: level already there")
                }
                Verdict::Refuse(why) => tracing::warn!(
                    amendment = a.id, %group, unit = a.unit, reason = why,
                    "inertia amendment refused: the article keeps its inertia"
                ),
            }
            if v == Verdict::Apply && publish_path.is_some() {
                state.publish_wake.notify_one();
            }
            out.push(Outcome { amendment: a.id, group, verdict: v });
        }
    }
    Ok(out)
}

/// The seed must hold the level the amendment gives: a seed edited later never
/// reaches a base by this way.
fn seed_says(seeds: &[SeedDoc], a: &InertiaAmendment) -> bool {
    let level = seeds.iter().find(|s| s.slug == a.doc).and_then(|s| s.units.iter().find(|u| u.code == a.unit));
    match level {
        Some(u) if u.level().get() == a.to => true,
        Some(u) if a.superseded_by.is_some() => {
            tracing::debug!(
                amendment = a.id,
                unit = a.unit,
                seed_level = u.level().get(),
                superseded_by = a.superseded_by,
                "inertia amendment superseded: nothing decided"
            );
            false
        }
        _ => {
            tracing::error!(
                amendment = a.id,
                doc = a.doc,
                unit = a.unit,
                "inertia amendment: the seed does not give this level, nothing decided"
            );
            false
        }
    }
}

async fn facts(conn: &mut SqliteConnection, unit_id: &str, raw: String) -> anyhow::Result<Facts> {
    let voted_changes: i64 = sqlx::query_scalar(
        "SELECT (SELECT COUNT(*) FROM adoptions WHERE unit_id = ?1 AND kind = 'inertia')
              + (SELECT COUNT(*) FROM inertia_changes WHERE unit_id = ?1 AND cause = 'vote')",
    )
    .bind(unit_id)
    .fetch_one(&mut *conn)
    .await?;
    let open_proposals: i64 =
        sqlx::query_scalar("SELECT COUNT(*) FROM proposals WHERE unit_id = ? AND kind = 'inertia' AND status = 'open'")
            .bind(unit_id)
            .fetch_one(&mut *conn)
            .await?;
    Ok(Facts { raw, voted_changes, open_proposals })
}

/// One document, in one transaction: `None` when it was decided at an earlier start.
async fn decide(
    state: &AppState,
    a: &InertiaAmendment,
    doc_id: &str,
    publishes: bool,
) -> anyhow::Result<Option<(Verdict, i64)>> {
    let mut tx = state.db.begin().await?;
    let decided: i64 =
        sqlx::query_scalar("SELECT COUNT(*) FROM inertia_amendments WHERE amendment_id = ? AND doc_id = ?")
            .bind(a.id)
            .bind(doc_id)
            .fetch_one(&mut *tx)
            .await?;
    if decided > 0 {
        return Ok(None);
    }
    let unit: Option<(String, String)> = sqlx::query_as("SELECT id, inertia FROM units WHERE doc_id = ? AND code = ?")
        .bind(doc_id)
        .bind(a.unit)
        .fetch_optional(&mut *tx)
        .await?;
    let found = match &unit {
        Some((id, raw)) => Some(facts(&mut tx, id, raw.clone()).await?),
        None => None,
    };
    let mut v = verdict(found.as_ref(), a);
    let now = util::now();
    let to = InertiaLevel::new(a.to).map(InertiaLevel::as_db).unwrap_or_default();
    if let (Verdict::Apply, Some((unit_id, raw))) = (v, &unit) {
        // Written only over the level that was judged.
        let done = sqlx::query("UPDATE units SET inertia = ? WHERE id = ? AND inertia = ?")
            .bind(&to)
            .bind(unit_id)
            .bind(raw)
            .execute(&mut *tx)
            .await?;
        if done.rows_affected() == 1 {
            sqlx::query(
                "INSERT INTO inertia_changes (unit_id, doc_id, from_level, to_level, cause, amendment_id, at)
                 VALUES (?, ?, ?, ?, 'amendment', ?, ?)",
            )
            .bind(unit_id)
            .bind(doc_id)
            .bind(a.from.to_string())
            .bind(&to)
            .bind(a.id)
            .bind(&now)
            .execute(&mut *tx)
            .await?;
            if publishes {
                sqlx::query("INSERT INTO outbox (doc_id, reason, created_at, next_at) VALUES (?, ?, ?, ?)")
                    .bind(doc_id)
                    .bind(a.reason)
                    .bind(&now)
                    .bind(&now)
                    .execute(&mut *tx)
                    .await?;
            }
        } else {
            v = Verdict::Refuse("changed");
        }
    }
    let (outcome, reason) = match v {
        Verdict::Apply => ("applied", None),
        Verdict::Present => ("present", None),
        Verdict::Refuse(why) => ("refused", Some(why)),
    };
    sqlx::query(
        "INSERT INTO inertia_amendments (amendment_id, doc_id, unit_code, from_level, to_level, outcome, reason, at)
         VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
    )
    .bind(a.id)
    .bind(doc_id)
    .bind(a.unit)
    .bind(unit.as_ref().map(|(_, raw)| raw.clone()))
    .bind(&to)
    .bind(outcome)
    .bind(reason)
    .bind(&now)
    .execute(&mut *tx)
    .await?;
    tx.commit().await?;
    Ok(Some((v, found.map_or(0, |f| f.open_proposals))))
}

#[cfg(test)]
mod tests {
    use super::*;

    const A: InertiaAmendment = InertiaAmendment {
        id: "test",
        doc: "doc",
        unit: "E1",
        from: 3,
        to: 4,
        reason: "inertie de départ relevée",
        superseded_by: None,
    };

    fn at(raw: &str) -> Facts {
        Facts { raw: raw.into(), ..Facts::default() }
    }

    #[test]
    fn the_starting_level_is_raised() {
        assert_eq!(verdict(Some(&at("3")), &A), Verdict::Apply);
        // The word of before, if an older image wrote it.
        assert_eq!(verdict(Some(&at("standard")), &A), Verdict::Apply);
    }

    #[test]
    fn an_open_change_of_inertia_does_not_stop_it() {
        let f = Facts { open_proposals: 1, ..at("3") };
        assert_eq!(verdict(Some(&f), &A), Verdict::Apply);
    }

    #[test]
    fn the_level_already_there_is_left_as_it_is() {
        assert_eq!(verdict(Some(&at("4")), &A), Verdict::Present);
        assert_eq!(verdict(Some(&at("high")), &A), Verdict::Present);
    }

    #[test]
    fn a_vote_on_the_inertia_keeps_it() {
        let cases = [
            (None, "no_article"),
            (Some(Facts { voted_changes: 1, ..at("3") }), "changed_by_vote"),
            (Some(at("5")), "level_differs"),
            (Some(at("2")), "level_differs"),
            (Some(at("haute")), "level_unreadable"),
        ];
        for (facts, reason) in cases {
            assert_eq!(verdict(facts.as_ref(), &A), Verdict::Refuse(reason), "{facts:?}");
        }
    }
}