//! Objections « redit » / « contredit » (2026-10-31, lot F, L12, ADR 0010).
//!
//! The rules are the engine's (`ld_engine::objection`): the latest arrival of
//! the pair, never a version in force, is no longer votable while the objection
//! stands; its author answers (a substantive revision, or a proposal linked to
//! the objection — a revision of the other side answers too); the objector is
//! then asked, by a message, to lift or reiterate; without an answer within 3
//! days the objection is lifted (`due`, run by the sweeper and at start).
//!
//! Objections live in the table of the contradiction signals of before
//! (`signals`, migration 0008): an older image still reads them as signals, and
//! every lifting writes `lifted_at` / `lifted_by` as it did.

use crate::AppState;
use crate::adoption;
use crate::auth::{IdentityRow, User};
use crate::docs::{self, DocState, UnitRow};
use crate::error::{AppError, AppResult};
use crate::messages::{self, Topic};
use crate::proposals;
use crate::util;
use axum::Json;
use axum::extract::{Path, State};
use ld_engine::edit;
use ld_engine::objection::{
    self, Change, Effect, Event, Lift, ObjectionKind, Phase, Refusal, Side, Step, Touched, Who,
};
use serde::Deserialize;
use serde_json::{Value, json};
use std::collections::{HashMap, HashSet};

pub const MIN_REASON: usize = 10;
pub const MAX_REASON: usize = 600;

#[derive(Clone, Debug, sqlx::FromRow)]
pub struct ObjectionRow {
    pub id: String,
    /// The version the objection was raised from.
    pub proposal_id: String,
    /// The version it was raised against.
    pub target_proposal_id: String,
    pub reason: String,
    /// The objector.
    pub author_id: String,
    pub created_at: String,
    pub lifted_at: Option<String>,
    pub lifted_by: Option<String>,
    pub kind: String,
    /// The version held back (not votable).
    pub held_id: Option<String>,
    pub phase: String,
    pub cycle: i64,
    pub due_at: Option<String>,
    pub answered_at: Option<String>,
    pub answer: Option<String>,
    pub answer_id: Option<String>,
    pub lift: Option<String>,
}

const SELECT: &str = "SELECT id, proposal_id, target_proposal_id, reason, author_id, created_at, lifted_at, lifted_by,
    kind, held_id, phase, cycle, due_at, answered_at, answer, answer_id, lift FROM signals";

impl ObjectionRow {
    pub fn phase(&self) -> Phase {
        let cycle = u32::try_from(self.cycle).unwrap_or(1);
        match self.phase.as_str() {
            "objector" => Phase::Objector { cycle, due: self.due_at.clone().unwrap_or_default() },
            "lifted" => Phase::Lifted(self.lift.as_deref().and_then(Lift::parse).unwrap_or(Lift::Objector)),
            _ => Phase::Author { cycle },
        }
    }

    pub fn kind(&self) -> ObjectionKind {
        ObjectionKind::parse(&self.kind).unwrap_or(ObjectionKind::Contredit)
    }

    /// The version the held one is said to repeat or contradict.
    pub fn other_id(&self) -> &str {
        if self.held_id.as_deref() == Some(self.proposal_id.as_str()) {
            &self.target_proposal_id
        } else {
            &self.proposal_id
        }
    }

    fn touches(&self, id: &str) -> Option<Touched> {
        if self.held_id.as_deref() == Some(id) {
            Some(Touched::Target)
        } else if self.proposal_id == id || self.target_proposal_id == id {
            Some(Touched::Other)
        } else {
            None
        }
    }
}

async fn load(state: &AppState, id: &str) -> AppResult<ObjectionRow> {
    sqlx::query_as::<_, ObjectionRow>(&format!("{SELECT} WHERE id = ?"))
        .bind(id)
        .fetch_optional(&state.db)
        .await?
        .ok_or(AppError::NotFound)
}

/// Standing objections touching one version, either side.
async fn standing_around(state: &AppState, proposal_id: &str) -> AppResult<Vec<ObjectionRow>> {
    Ok(sqlx::query_as::<_, ObjectionRow>(&format!(
        "{SELECT} WHERE phase <> 'lifted' AND (proposal_id = ?1 OR target_proposal_id = ?1) ORDER BY created_at, rowid"
    ))
    .bind(proposal_id)
    .fetch_all(&state.db)
    .await?)
}

/// For a document: the versions held back by a standing objection (never one in
/// force), and how many standing objections touch each version.
pub async fn held(
    state: &AppState,
    doc_id: &str,
    units: &[UnitRow],
) -> AppResult<(HashSet<String>, HashMap<String, i64>)> {
    let rows = sqlx::query_as::<_, ObjectionRow>(&format!(
        "{SELECT} WHERE phase <> 'lifted' AND proposal_id IN
           (SELECT p.id FROM proposals p JOIN units u ON u.id = p.unit_id WHERE u.doc_id = ?)"
    ))
    .bind(doc_id)
    .fetch_all(&state.db)
    .await?;
    let in_force: HashSet<&str> = units.iter().filter_map(|u| u.in_force_id.as_deref()).collect();
    let mut held = HashSet::new();
    let mut counts: HashMap<String, i64> = HashMap::new();
    for o in &rows {
        *counts.entry(o.proposal_id.clone()).or_default() += 1;
        *counts.entry(o.target_proposal_id.clone()).or_default() += 1;
        if let Some(h) = &o.held_id
            && !objection::votable(h, in_force.contains(h.as_str()), &[h.as_str()])
        {
            held.insert(h.clone());
        }
    }
    Ok((held, counts))
}

/// The order a version arrived in: its submission (or creation), then the order it was written in.
async fn arrival(state: &AppState, p: &docs::ProposalRow) -> AppResult<(String, i64)> {
    let seq: i64 =
        sqlx::query_scalar("SELECT rowid FROM proposals WHERE id = ?").bind(&p.id).fetch_one(&state.db).await?;
    Ok((p.submitted_at.clone().unwrap_or_else(|| p.created_at.clone()), seq))
}

fn is_in_force(st: &DocState, id: &str) -> bool {
    st.units.iter().any(|u| u.in_force_id.as_deref() == Some(id))
}

fn who(user: &IdentityRow, objector: &str) -> Who {
    let me = user.to_identity();
    if trustin_access::reiterates_objection(&me, objector) {
        Who::Objector
    } else if trustin_access::lifts_objection(&me, objector) {
        Who::Admin
    } else {
        Who::Other
    }
}

fn refused(r: Refusal) -> AppError {
    match r {
        Refusal::Lifted => AppError::Conflict("lifted"),
        Refusal::NotYours => AppError::Forbidden,
        Refusal::NothingToReiterate => AppError::Conflict("nothing_to_reiterate"),
    }
}

async fn author_of(state: &AppState, proposal_id: &str) -> AppResult<Option<String>> {
    Ok(sqlx::query_scalar::<_, Option<String>>("SELECT author_id FROM proposals WHERE id = ?")
        .bind(proposal_id)
        .fetch_optional(&state.db)
        .await?
        .flatten())
}

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

/// Stores a step, only over the phase it was computed from (two people acting at
/// once: the second gets a conflict), then does its effects. Returns false when
/// the phase had changed meanwhile.
async fn store(
    state: &AppState,
    o: &ObjectionRow,
    step: &Step,
    by: &str,
    extra: Option<(&str, &str)>,
) -> AppResult<bool> {
    let now = state.clock.now();
    let (phase, cycle, due, lift) = match &step.phase {
        Phase::Author { cycle } => ("author", i64::from(*cycle), None, None),
        Phase::Objector { cycle, due } => ("objector", i64::from(*cycle), Some(due.clone()), None),
        Phase::Lifted(l) => ("lifted", o.cycle, None, Some(*l)),
    };
    let (answer, answer_id) =
        extra.map_or((o.answer.clone(), o.answer_id.clone()), |(a, id)| (Some(a.into()), Some(id.into())));
    let answered_at = if extra.is_some() { Some(now.clone()) } else { o.answered_at.clone() };
    let done = sqlx::query(
        "UPDATE signals SET phase = ?, cycle = ?, due_at = ?, lift = ?, answer = ?, answer_id = ?, answered_at = ?,
           lifted_at = CASE WHEN ? = 'lifted' THEN ? ELSE lifted_at END,
           lifted_by = CASE WHEN ? = 'lifted' THEN ? ELSE lifted_by END
         WHERE id = ? AND phase = ? AND cycle = ?",
    )
    .bind(phase)
    .bind(cycle)
    .bind(&due)
    .bind(lift.map(Lift::as_str))
    .bind(&answer)
    .bind(&answer_id)
    .bind(&answered_at)
    .bind(phase)
    .bind(&now)
    .bind(phase)
    .bind(by)
    .bind(&o.id)
    .bind(&o.phase)
    .bind(o.cycle)
    .execute(&state.db)
    .await?;
    if done.rows_affected() != 1 {
        return Ok(false);
    }
    let doc_id = doc_of(state, &o.proposal_id).await?;
    let held_author = match &o.held_id {
        Some(h) => author_of(state, h).await?,
        None => None,
    };
    for effect in &step.effects {
        match effect {
            Effect::AskObjector => {
                // The author's question of this cycle is answered.
                messages::close(
                    state,
                    Topic::Objection,
                    &o.id,
                    Some(&["objection_raised", "objection_reiterated"]),
                    "answered",
                )
                .await?;
                if held_author.as_deref() != Some(o.author_id.as_str()) {
                    messages::notify(
                        state,
                        &o.author_id,
                        &doc_id,
                        Topic::Objection,
                        &o.id,
                        "objection_answered",
                        cycle,
                        due.as_deref(),
                    )
                    .await?;
                }
            }
            Effect::TellAuthor => {
                messages::close(state, Topic::Objection, &o.id, Some(&["objection_answered"]), "reiterated").await?;
                if let Some(author) = held_author.as_deref().filter(|a| *a != o.author_id) {
                    messages::notify(
                        state,
                        author,
                        &doc_id,
                        Topic::Objection,
                        &o.id,
                        "objection_reiterated",
                        cycle,
                        None,
                    )
                    .await?;
                }
            }
            Effect::Ended => {
                let outcome = match lift {
                    Some(Lift::Admin) => "admin",
                    Some(Lift::Deadline) => "deadline",
                    Some(Lift::Withdrawn) => "withdrawn",
                    _ => "lifted",
                };
                messages::close(state, Topic::Objection, &o.id, None, outcome).await?;
            }
        }
    }
    Ok(true)
}

// ---------------------------------------------------------------------------
// Raise, lift, reiterate
// ---------------------------------------------------------------------------

#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct RaiseBody {
    other_id: String,
    kind: String,
    reason: String,
}

/// `POST /api/proposals/{id}/objections` — « this version repeats (or
/// contradicts) that one ». The latest arrival of the two is held back.
pub async fn raise(
    State(state): State<AppState>,
    User(user): User,
    Path(id): Path<String>,
    Json(b): Json<RaiseBody>,
) -> AppResult<Json<Value>> {
    let (p, st) = proposals::guarded(&state, &user, &id).await?;
    let reason = b.reason.trim();
    if reason.chars().count() < MIN_REASON || reason.chars().count() > MAX_REASON || edit::has_hidden_controls(reason) {
        return Err(AppError::Invalid("reason"));
    }
    let kind = ObjectionKind::parse(&b.kind).ok_or(AppError::Invalid("kind"))?;
    let other = st.proposals.iter().find(|x| x.id == b.other_id).ok_or(AppError::Invalid("other"))?;
    let voted = |x: &docs::ProposalRow| matches!(x.status.as_str(), "open" | "in_force") && x.kind == "text";
    if other.id == p.id || !voted(other) || !voted(&p) {
        return Err(AppError::Invalid("other"));
    }
    if other.unit_id == p.unit_id {
        // Rivals on one article never stand together anyway.
        return Err(AppError::Invalid("same_unit"));
    }
    let (pa, oa) = (arrival(&state, &p).await?, arrival(&state, other).await?);
    let held = objection::target(
        &Side { id: &p.id, arrived_at: &pa.0, seq: pa.1, in_force: is_in_force(&st, &p.id) },
        &Side { id: &other.id, arrived_at: &oa.0, seq: oa.1, in_force: is_in_force(&st, &other.id) },
    )
    .map_err(|e| match e {
        objection::PairError::BothInForce => AppError::Invalid("both_in_force"),
        objection::PairError::Same => AppError::Invalid("other"),
    })?
    .to_owned();
    let exists: i64 = sqlx::query_scalar(
        "SELECT COUNT(*) FROM signals WHERE phase <> 'lifted' AND author_id = ?
           AND ((proposal_id = ?2 AND target_proposal_id = ?3) OR (proposal_id = ?3 AND target_proposal_id = ?2))",
    )
    .bind(&user.id)
    .bind(&p.id)
    .bind(&other.id)
    .fetch_one(&state.db)
    .await?;
    if exists > 0 {
        return Err(AppError::Conflict("objection_exists"));
    }
    let oid = util::id();
    sqlx::query(
        "INSERT INTO signals (id, proposal_id, target_proposal_id, reason, author_id, created_at, kind, held_id, phase, cycle)
         VALUES (?, ?, ?, ?, ?, ?, ?, ?, 'author', 1)",
    )
    .bind(&oid)
    .bind(&p.id)
    .bind(&other.id)
    .bind(reason)
    .bind(&user.id)
    .bind(state.clock.now())
    .bind(kind.as_str())
    .bind(&held)
    .execute(&state.db)
    .await?;
    if let Some(author) = author_of(&state, &held).await?.filter(|a| *a != user.id) {
        messages::notify(&state, &author, &st.doc.id, Topic::Objection, &oid, "objection_raised", 1, None).await?;
    }
    tracing::info!(objection = %oid, held = %held, kind = kind.as_str(), "objection raised");
    Ok(Json(json!({ "id": oid, "heldId": held })))
}

async fn act(state: &AppState, user: &IdentityRow, id: &str, lift: bool) -> AppResult<ObjectionRow> {
    let o = load(state, id).await?;
    proposals::guarded(state, user, &o.proposal_id).await?;
    let event = if lift { Event::Lift(who(user, &o.author_id)) } else { Event::Reiterate(who(user, &o.author_id)) };
    let step = objection::step(&o.phase(), &event).map_err(refused)?.ok_or(AppError::Conflict("lifted"))?;
    if !store(state, &o, &step, &user.id, None).await? {
        return Err(AppError::Conflict("changed"));
    }
    messages::read_subject(state, &user.id, Topic::Objection, &o.id).await?;
    tracing::info!(objection = %o.id, lift, by = %user.id, "objection lifted or reiterated");
    Ok(o)
}

/// `POST /api/objections/{id}/lift` — by the objector, or an administrator.
pub async fn lift(State(state): State<AppState>, User(user): User, Path(id): Path<String>) -> AppResult<Json<Value>> {
    let o = act(&state, &user, &id, true).await?;
    let entered = adoption::run(&state, &doc_of(&state, &o.proposal_id).await?).await?;
    Ok(Json(json!({ "entered": entered })))
}

/// `POST /api/objections/{id}/reiterate` — by the objector only, once the author answered.
pub async fn reiterate(
    State(state): State<AppState>,
    User(user): User,
    Path(id): Path<String>,
) -> AppResult<Json<Value>> {
    act(&state, &user, &id, false).await?;
    Ok(Json(json!({ "ok": true })))
}

// ---------------------------------------------------------------------------
// What answers an objection
// ---------------------------------------------------------------------------

/// A version changed (by `by`): the objections around it whose author it
/// answers move on; the messages of the one who answered are read.
pub async fn on_change(state: &AppState, proposal_id: &str, substantive: bool, by: &str) -> AppResult<()> {
    for o in standing_around(state, proposal_id).await? {
        let Some(side) = o.touches(proposal_id) else { continue };
        let change = if substantive { Change::Revision(side) } else { Change::Typo(side) };
        if !objection::answers(change) {
            continue;
        }
        let due = state.clock.in_days(objection::ANSWER_DAYS);
        if let Some(step) = objection::step(&o.phase(), &Event::Answered { due: &due }).map_err(refused)? {
            let answer = if side == Touched::Target { "revision" } else { "other" };
            if store(state, &o, &step, proposal_id, Some((answer, proposal_id))).await? {
                messages::read_subject(state, by, Topic::Objection, &o.id).await?;
            }
        }
    }
    Ok(())
}

/// May this person write a proposal linked to this objection, on this article?
pub async fn check_link(state: &AppState, user: &IdentityRow, objection_id: &str, unit_id: &str) -> AppResult<()> {
    let o = load(state, objection_id).await.map_err(|_| AppError::Invalid("link"))?;
    let held = o.held_id.as_deref().ok_or(AppError::Invalid("link"))?;
    let unit_of = |id: String| async move {
        sqlx::query_scalar::<_, String>("SELECT unit_id FROM proposals WHERE id = ?")
            .bind(id)
            .fetch_one(&state.db)
            .await
    };
    let (held_unit, other_unit) = (unit_of(held.to_owned()).await?, unit_of(o.other_id().to_owned()).await?);
    let author = author_of(state, held).await?;
    if !o.phase().standing()
        || !objection::may_link(author.as_deref(), &user.id)
        || !objection::link_fits(unit_id, &held_unit, &other_unit)
    {
        return Err(AppError::Invalid("link"));
    }
    Ok(())
}

/// A proposal linked to an objection was submitted (by `by`): it answers the objection.
pub async fn on_linked(state: &AppState, objection_id: &str, proposal_id: &str, by: &str) -> AppResult<()> {
    let o = load(state, objection_id).await?;
    if !objection::answers(Change::LinkedProposal) {
        return Ok(());
    }
    let due = state.clock.in_days(objection::ANSWER_DAYS);
    if let Some(step) = objection::step(&o.phase(), &Event::Answered { due: &due }).map_err(refused)?
        && store(state, &o, &step, proposal_id, Some(("proposal", proposal_id))).await?
    {
        messages::read_subject(state, by, Topic::Objection, &o.id).await?;
    }
    Ok(())
}

/// A version was withdrawn: the objections around it end.
pub async fn on_withdrawn(state: &AppState, proposal_id: &str, by: &str) -> AppResult<()> {
    for o in standing_around(state, proposal_id).await? {
        if let Some(step) = objection::step(&o.phase(), &Event::Withdrawn).map_err(refused)? {
            store(state, &o, &step, by, None).await?;
        }
    }
    Ok(())
}

/// The objections whose deadline passed are lifted by themselves; returns how
/// many, and the documents touched.
pub async fn due(state: &AppState) -> AppResult<(usize, Vec<String>)> {
    let now = state.clock.now();
    let rows = sqlx::query_as::<_, ObjectionRow>(&format!("{SELECT} WHERE phase = 'objector' AND due_at <= ?"))
        .bind(&now)
        .fetch_all(&state.db)
        .await?;
    let mut docs = Vec::new();
    let mut lifted = 0;
    for o in rows {
        if let Some(step) = objection::step(&o.phase(), &Event::Tick { now: &now }).map_err(refused)?
            && store(state, &o, &step, "deadline", None).await?
        {
            tracing::info!(objection = %o.id, "objection lifted at its deadline");
            lifted += 1;
            let doc = doc_of(state, &o.proposal_id).await?;
            if !docs.contains(&doc) {
                docs.push(doc);
            }
        }
    }
    Ok((lifted, docs))
}

// ---------------------------------------------------------------------------
// What the screen shows
// ---------------------------------------------------------------------------

fn version_json(st: &DocState, id: &str) -> Value {
    let p = st.proposals.iter().find(|p| p.id == id);
    let unit = p.and_then(|p| st.units.iter().find(|u| u.id == p.unit_id));
    json!({
        "id": id, "title": p.map(|p| &p.title), "status": p.map(|p| &p.status), "unitId": p.map(|p| &p.unit_id),
        "code": unit.map(|u| &u.code), "author": p.and_then(|p| p.author_name.as_ref()),
        "authorId": p.and_then(|p| p.author_id.as_ref()),
    })
}

async fn name_of(state: &AppState, id: &str) -> AppResult<(Option<String>, bool)> {
    let row: Option<(String, bool)> =
        sqlx::query_as("SELECT display_name, kind = 'invite' FROM identities WHERE id = ?")
            .bind(id)
            .fetch_optional(&state.db)
            .await?;
    Ok(row.map_or((None, false), |(n, i)| (Some(n), i)))
}

/// One objection, as `viewer` sees it: who raised it, what it holds back, where
/// it stands, and what the viewer may do.
pub async fn view(state: &AppState, st: &DocState, viewer: &IdentityRow, o: &ObjectionRow) -> AppResult<Value> {
    let (objector, invited) = name_of(state, &o.author_id).await?;
    let phase = o.phase();
    let held_author = match &o.held_id {
        Some(h) => author_of(state, h).await?,
        None => None,
    };
    let me = viewer.to_identity();
    let standing = phase.standing();
    let i_answer = standing && o.held_id.is_some() && objection::may_link(held_author.as_deref(), &viewer.id);
    let asked = matches!(phase, Phase::Objector { .. });
    Ok(json!({
        "id": o.id, "kind": o.kind(), "reason": o.reason, "objector": objector, "objectorInvited": invited,
        "mine": o.author_id == viewer.id, "at": o.created_at,
        "phase": o.phase, "cycle": o.cycle, "dueAt": o.due_at, "answer": o.answer, "answerId": o.answer_id,
        "answeredAt": o.answered_at, "lift": o.lift, "liftedAt": o.lifted_at,
        "heldVersion": o.held_id.as_ref().map(|h| version_json(st, h)),
        "other": version_json(st, o.other_id()),
        "iAnswer": i_answer,
        "canLift": standing && trustin_access::lifts_objection(&me, &o.author_id),
        "canReiterate": asked && trustin_access::reiterates_objection(&me, &o.author_id),
    }))
}

/// The objections around one version, newest first, each as `viewer` sees it;
/// `held` tells whether this version is the one held back.
pub async fn around(state: &AppState, st: &DocState, viewer: &IdentityRow, proposal_id: &str) -> AppResult<Vec<Value>> {
    let rows = sqlx::query_as::<_, ObjectionRow>(&format!(
        "{SELECT} WHERE proposal_id = ?1 OR target_proposal_id = ?1 ORDER BY created_at DESC, rowid DESC"
    ))
    .bind(proposal_id)
    .fetch_all(&state.db)
    .await?;
    let mut out = Vec::with_capacity(rows.len());
    for o in rows {
        let mut v = view(state, st, viewer, &o).await?;
        v["held"] = json!(o.held_id.as_deref() == Some(proposal_id));
        out.push(v);
    }
    Ok(out)
}

/// An objection, for a message of its box: what it is about, and the gestures
/// the message offers now (none once dealt with).
pub async fn for_message(
    state: &AppState,
    viewer: &IdentityRow,
    subject_id: &str,
    kind: &str,
    cycle: i64,
) -> AppResult<Option<(Value, Vec<&'static str>)>> {
    let Ok(o) = load(state, subject_id).await else { return Ok(None) };
    let st = docs::load_state(state, &doc_of(state, &o.proposal_id).await?).await?;
    let v = view(state, &st, viewer, &o).await?;
    let current = o.cycle == cycle;
    let gestures = match (o.phase(), kind) {
        (Phase::Author { .. }, "objection_raised" | "objection_reiterated") if current => vec!["respond"],
        (Phase::Objector { .. }, "objection_answered") if current && o.author_id == viewer.id => {
            vec!["lift", "reiterate"]
        }
        _ => vec![],
    };
    Ok(Some((v, gestures)))
}