//! Generate snapshot fixtures from the Gauntlet test world (D-030 full pipeline).
//!
//! Runs the full Gauntlet simulation pipeline — same code path as --test-mode —
//! then serializes ObserverSnapshots to both MessagePack (wire format) and JSON
//! (human-readable debug) for client-side visual testing.
//!
//! The .msgpack files are the actual wire-format bytes the server sends over IPC.
//! Client visual tests load them via Protocol.decode_snapshot() → GameState.apply_snapshot(),
//! exercising the exact same pipeline as the live game.
//!
//! The .json files are for human inspection only.
//!
//! Run with: cargo test --test gen_gauntlet_fixtures -- --ignored
//! Or:       make fixtures-gauntlet
//!
//! Output: tests/fixtures/gauntlet/*.{msgpack,json} (relative to repo root)

use settled_reach_server::bridge::types::*;
use settled_reach_server::bridge::{BridgePlugin, SnapshotBuffer};
use settled_reach_server::knowledge::KnowledgePlugin;
use settled_reach_server::npc::NpcPlugin;
use settled_reach_server::perception::vision_cone::Facing;
use settled_reach_server::simulation::movement::{PlayerCharacter, TilePosition};
use settled_reach_server::simulation::rng::SimRng;
use settled_reach_server::simulation::SimulationPlugin;
use settled_reach_server::test_world;

use bevy_app::prelude::*;
use bevy_ecs::prelude::*;
use serde_json::Value;
use std::collections::BTreeMap;
use std::fs;
use std::path::Path;

const SEED: u64 = 42;
const FIXTURE_DIR: &str = "../tests/fixtures/gauntlet";

/// Build a deterministic Gauntlet simulation app.
/// Identical to what the server runs in --test-mode.
fn build_gauntlet(seed: u64) -> App {
    let mut app = App::new();
    app.add_plugins(SimulationPlugin);
    app.add_plugins(BridgePlugin);
    app.add_plugins(KnowledgePlugin);
    app.add_plugins(NpcPlugin);
    app.insert_resource(SimRng::new(seed));

    test_world::setup_gauntlet(
        &mut app,
        settled_reach_server::bridge::types::CharacterArchetype::default(),
    );

    app
}

/// Teleport the player to a specific position and facing.
/// Directly modifies ECS components — same effect as PlayerAction::Teleport
/// but without needing a target room action.
fn teleport_player(app: &mut App, pos: TilePosition, facing: Facing) {
    let player = {
        let mut query = app
            .world_mut()
            .query_filtered::<Entity, With<PlayerCharacter>>();
        query.single(app.world()).expect("player entity must exist")
    };
    app.world_mut().entity_mut(player).insert((pos, facing));
}

/// Run N ticks, feeding inputs each tick, return the last snapshot.
fn run_ticks(app: &mut App, inputs: &[Vec<PlayerInput>]) -> ObserverSnapshot {
    let mut last_snapshot: Option<ObserverSnapshot> = None;

    for tick_inputs in inputs {
        {
            let mut queue = app
                .world_mut()
                .resource_mut::<settled_reach_server::simulation::input::InputQueue>();
            for input in tick_inputs {
                queue.push(input.clone());
            }
        }

        app.update();

        let buffer = app.world().resource::<SnapshotBuffer>();
        if let Some(snapshot) = &buffer.snapshot {
            last_snapshot = Some(snapshot.clone());
        }
    }

    last_snapshot.expect("no snapshot produced")
}

/// Recursively sort all object keys for deterministic JSON output.
fn sort_json_keys(value: &Value) -> Value {
    match value {
        Value::Object(map) => {
            let sorted: BTreeMap<String, Value> = map
                .iter()
                .map(|(k, v)| (k.clone(), sort_json_keys(v)))
                .collect();
            Value::Object(sorted.into_iter().collect())
        }
        Value::Array(arr) => Value::Array(arr.iter().map(sort_json_keys).collect()),
        other => other.clone(),
    }
}

fn write_fixture(name: &str, snapshot: &ObserverSnapshot) {
    let dir = Path::new(env!("CARGO_MANIFEST_DIR")).join(FIXTURE_DIR);
    fs::create_dir_all(&dir).expect("create fixture dir");

    // MessagePack — exact wire-format bytes the server sends over IPC.
    // Client visual tests load these via Protocol.decode_snapshot().
    let msgpack = rmp_serde::to_vec_named(snapshot).expect("serialize to MessagePack");
    let msgpack_path = dir.join(format!("{}.msgpack", name));
    fs::write(&msgpack_path, &msgpack).expect("write msgpack fixture");

    // JSON — human-readable debug companion (not loaded by tests).
    let value: Value = serde_json::to_value(snapshot).expect("serialize to JSON");
    let sorted = sort_json_keys(&value);
    let json = serde_json::to_string_pretty(&sorted).expect("format JSON") + "\n";
    let json_path = dir.join(format!("{}.json", name));
    fs::write(&json_path, &json).expect("write json fixture");

    eprintln!(
        "Wrote {} ({} bytes msgpack, {} bytes json, {} visible_tiles, {} entities)",
        name,
        msgpack.len(),
        json.len(),
        snapshot.visible_tiles.len(),
        snapshot.entities.len(),
    );
}

#[test]
#[ignore] // Run manually: cargo test --test gen_gauntlet_fixtures -- --ignored
fn generate_gauntlet_snapshot_fixtures() {
    // --- Hub (default spawn position) ---
    // Player at (50, 58) facing North — tests fog rendering at the starting location.
    // This is the exact state a new player sees on connect.
    {
        let mut app = build_gauntlet(SEED);
        // Run 3 idle ticks to stabilize (cognitive delay, vision cone init)
        let inputs: Vec<Vec<PlayerInput>> = vec![vec![], vec![], vec![]];
        let snapshot = run_ticks(&mut app, &inputs);
        write_fixture("hub_spawn", &snapshot);
    }

    // --- Fog Theater (observer position) ---
    // Player at (56, 18) facing South — large open room with NPCs at varying distances.
    // Tests visibility cone, fog layers, and distance-based fog rendering.
    {
        let mut app = build_gauntlet(SEED);
        let fog_theater = test_world::constants::FOG_THEATER;
        teleport_player(&mut app, fog_theater.observer, fog_theater.observer_facing);
        let inputs: Vec<Vec<PlayerInput>> = vec![vec![], vec![], vec![]];
        let snapshot = run_ticks(&mut app, &inputs);
        write_fixture("fog_theater", &snapshot);
    }

    // --- Hub after movement (explored tiles + visible tiles differ) ---
    // Player moves south from hub, creating a mix of explored-but-not-visible
    // and currently-visible tiles — the exact fog boundary condition.
    {
        let mut app = build_gauntlet(SEED);
        let inputs: Vec<Vec<PlayerInput>> = vec![
            vec![],
            vec![PlayerInput {
                tick: 1,
                action: PlayerAction::MoveSouth,
            }],
            vec![PlayerInput {
                tick: 2,
                action: PlayerAction::MoveSouth,
            }],
            vec![PlayerInput {
                tick: 3,
                action: PlayerAction::MoveSouth,
            }],
            vec![], // idle — snapshot has explored + visible tiles that differ
        ];
        let snapshot = run_ticks(&mut app, &inputs);
        write_fixture("hub_after_movement", &snapshot);
    }
}