/// Transaction API routes.
///
/// POST /tx/apply              — apply a command
/// POST /tx/rollback/{id}      — roll back a command
/// GET  /tx/history?since={ms} — command history
/// GET  /tx/chain/{id}         — causal chain for a command
use axum::{
    extract::{Path, Query, State},
    http::StatusCode,
    Json,
};
use engram_tx::{Command, CommandResult};
use serde::{Deserialize, Serialize};
use std::sync::Arc;
use uuid::Uuid;

use crate::state::AppState;

// ── POST /tx/apply ────────────────────────────────────────────────────────────

pub async fn tx_apply(
    State(state): State<Arc<AppState>>,
    Json(cmd): Json<Command>,
) -> Result<Json<CommandResult>, StatusCode> {
    let mut engine = state
        .tx_engine
        .lock()
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    let result = engine
        .apply(cmd)
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    Ok(Json(result))
}

// ── POST /tx/rollback/{command_id} ───────────────────────────────────────────

#[derive(Serialize)]
pub struct RollbackResponse {
    pub rollback_command_id: Uuid,
    pub status: String,
}

pub async fn tx_rollback(
    State(state): State<Arc<AppState>>,
    Path(command_id): Path<Uuid>,
) -> Result<Json<RollbackResponse>, StatusCode> {
    let mut engine = state
        .tx_engine
        .lock()
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    let rb = engine
        .rollback(command_id)
        .map_err(|e| {
            tracing::warn!("rollback failed: {}", e);
            StatusCode::BAD_REQUEST
        })?;
    Ok(Json(RollbackResponse {
        rollback_command_id: rb.id,
        status: format!("{:?}", rb.status),
    }))
}

// ── GET /tx/history ───────────────────────────────────────────────────────────

#[derive(Deserialize)]
pub struct HistoryParams {
    pub since: Option<i64>,
}

#[derive(Serialize)]
pub struct HistoryResponse {
    pub commands: Vec<Command>,
}

pub async fn tx_history(
    State(state): State<Arc<AppState>>,
    Query(params): Query<HistoryParams>,
) -> Result<Json<HistoryResponse>, StatusCode> {
    let engine = state
        .tx_engine
        .lock()
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    let since = params.since.unwrap_or(0);
    let commands = engine
        .history(since)
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    Ok(Json(HistoryResponse { commands }))
}

// ── GET /tx/chain/{command_id} ────────────────────────────────────────────────

#[derive(Serialize)]
pub struct CausalChainResponse {
    pub chain: Vec<Command>,
}

pub async fn tx_causal_chain(
    State(state): State<Arc<AppState>>,
    Path(command_id): Path<Uuid>,
) -> Result<Json<CausalChainResponse>, StatusCode> {
    let engine = state
        .tx_engine
        .lock()
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    let chain = engine
        .causal_chain(command_id)
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    Ok(Json(CausalChainResponse { chain }))
}