// Input processing system
// Timestamped player input events for deterministic simulation (D-010 principle 4)
// PlayerInput: semantic actions (MoveNorth, Interact, UsePerceptionMode, ToggleStance)

use crate::bridge::types::{PlayerAction, PlayerInput};
use crate::perception::vision_cone::{facing_from_delta, Facing};
use crate::simulation::movement::{MoveIntent, PlayerCharacter, TilePosition};
use crate::simulation::stance::{PlayerMoveCooldown, Stance};
use crate::simulation::time::{SimulationTime, TickRate};
use bevy_ecs::prelude::*;
use std::collections::VecDeque;

/// Queue of pending player inputs, ordered by tick
#[derive(Resource, Debug, Default)]
pub struct InputQueue {
    queue: VecDeque<PlayerInput>,
}

impl InputQueue {
    /// Add a new input to the queue.
    /// Inputs must be pushed in tick order for deterministic processing.
    /// Panics in debug builds if tick ordering is violated.
    pub fn push(&mut self, input: PlayerInput) {
        debug_assert!(
            self.queue.back().is_none_or(|last| last.tick <= input.tick),
            "InputQueue: tick ordering violated (last={}, new={})",
            self.queue.back().map_or(0, |last| last.tick),
            input.tick,
        );
        self.queue.push_back(input);
    }

    /// Drain all inputs for ticks <= the given tick
    /// Returns inputs in FIFO order
    pub fn drain_for_tick(&mut self, tick: u64) -> Vec<PlayerInput> {
        let mut result = Vec::new();
        while let Some(front) = self.queue.front() {
            if front.tick <= tick {
                result.push(self.queue.pop_front().unwrap());
            } else {
                break;
            }
        }
        result
    }

    /// Get the current queue length
    pub fn len(&self) -> usize {
        self.queue.len()
    }

    /// Check if the queue is empty
    pub fn is_empty(&self) -> bool {
        self.queue.is_empty()
    }
}

/// Drains InputQueue for the current tick, converts PlayerActions to ECS components.
/// Handles stance toggling (D-053) and movement cooldown based on current stance.
#[allow(clippy::type_complexity)]
pub fn process_player_input(
    mut input_queue: ResMut<InputQueue>,
    mut time: ResMut<SimulationTime>,
    mut commands: Commands,
    mut player_query: Query<
        (Entity, &TilePosition, Option<&mut Stance>, Option<&mut PlayerMoveCooldown>),
        With<PlayerCharacter>,
    >,
) {
    let current_tick = time.tick;
    let inputs = input_queue.drain_for_tick(current_tick);

    // Track whether any movement was attempted this tick (for cooldown tick advance)
    let mut move_attempted = false;

    for input in inputs {
        match input.action {
            PlayerAction::MoveNorth => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, 0, -1);
            }
            PlayerAction::MoveSouth => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, 0, 1);
            }
            PlayerAction::MoveEast => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, 1, 0);
            }
            PlayerAction::MoveWest => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, -1, 0);
            }
            PlayerAction::MoveNortheast => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, 1, -1);
            }
            PlayerAction::MoveNorthwest => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, -1, -1);
            }
            PlayerAction::MoveSoutheast => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, 1, 1);
            }
            PlayerAction::MoveSouthwest => {
                move_attempted = true;
                apply_move(&mut player_query, &mut commands, -1, 1);
            }
            PlayerAction::ToggleStanceUp => {
                if let Ok((_, _, Some(mut stance), _)) = player_query.single_mut() {
                    let new_stance = stance.0.step_up();
                    if new_stance != stance.0 {
                        tracing::debug!("Stance up: {:?} -> {:?}", stance.0, new_stance);
                        stance.0 = new_stance;
                    }
                }
            }
            PlayerAction::ToggleStanceDown => {
                if let Ok((_, _, Some(mut stance), _)) = player_query.single_mut() {
                    let new_stance = stance.0.step_down();
                    if new_stance != stance.0 {
                        tracing::debug!("Stance down: {:?} -> {:?}", stance.0, new_stance);
                        stance.0 = new_stance;
                    }
                }
            }
            PlayerAction::Pause => {
                time.tick_rate = TickRate::Paused;
                tracing::debug!("Simulation paused by player input");
            }
            PlayerAction::Unpause => {
                time.tick_rate = TickRate::Full;
                tracing::debug!("Simulation unpaused by player input");
            }
            PlayerAction::SetTickRate(rate) => {
                time.tick_rate = rate;
                tracing::debug!("Tick rate set to {:?} by player input", rate);
            }
            PlayerAction::Interact { target_entity_id, verb } => {
                tracing::info!(
                    "Interact: target={:?}, verb={:?} — logged only, dialogue dispatch future scope (#415)",
                    target_entity_id,
                    verb,
                );
            }
            PlayerAction::UsePerceptionMode(ref mode) => {
                tracing::trace!("UsePerceptionMode({}) — no-op for Sprint 1", mode);
            }
        }
    }

    // If no movement was attempted this tick, still advance cooldown counter
    if !move_attempted {
        if let Ok((_, _, _, Some(mut cooldown))) = player_query.single_mut() {
            cooldown.tick();
        }
    }
}

/// Apply a movement action with stance-based cooldown enforcement.
/// If the player has a Stance and PlayerMoveCooldown, movement is throttled
/// according to the stance's ticks_per_move. Without these components,
/// movement is unrestricted (backward compatibility).
#[allow(clippy::type_complexity)]
fn apply_move(
    player_query: &mut Query<
        (Entity, &TilePosition, Option<&mut Stance>, Option<&mut PlayerMoveCooldown>),
        With<PlayerCharacter>,
    >,
    commands: &mut Commands,
    dx: i32,
    dy: i32,
) {
    let (entity, pos, stance_opt, cooldown_opt) = player_query
        .single_mut()
        .expect("PlayerCharacter entity must exist when processing input");

    let stance = stance_opt.map(|s| s.0).unwrap_or_default();

    // Check cooldown if present
    if let Some(mut cooldown) = cooldown_opt {
        if !cooldown.try_move(stance) {
            tracing::trace!("Movement throttled by stance {:?} cooldown", stance);
            return;
        }
    }

    commands.entity(entity).insert(MoveIntent {
        target: TilePosition::new(pos.x + dx, pos.y + dy, pos.z),
    });
    // Update facing direction based on movement (D-015 vision cone)
    commands
        .entity(entity)
        .insert(Facing(facing_from_delta(dx, dy)));
}

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

    #[test]
    fn drain_returns_inputs_up_to_tick() {
        let mut queue = InputQueue::default();
        queue.push(PlayerInput {
            tick: 1,
            action: PlayerAction::MoveNorth,
        });
        queue.push(PlayerInput {
            tick: 2,
            action: PlayerAction::MoveSouth,
        });
        queue.push(PlayerInput {
            tick: 5,
            action: PlayerAction::Interact { target_entity_id: None, verb: None },
        });
        let inputs = queue.drain_for_tick(3);
        assert_eq!(inputs.len(), 2);
        assert_eq!(queue.len(), 1);
    }

    #[test]
    fn drain_empty_queue_returns_empty() {
        let mut queue = InputQueue::default();
        let inputs = queue.drain_for_tick(10);
        assert!(inputs.is_empty());
    }

    #[test]
    #[should_panic(expected = "tick ordering violated")]
    fn push_rejects_out_of_order_in_debug() {
        let mut queue = InputQueue::default();
        queue.push(PlayerInput {
            tick: 5,
            action: PlayerAction::MoveNorth,
        });
        queue.push(PlayerInput {
            tick: 2,
            action: PlayerAction::MoveSouth,
        });
    }

    #[test]
    fn process_input_move_creates_intent() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        let player = world
            .spawn((PlayerCharacter, TilePosition::new(5, 5, 0)))
            .id();

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);
        schedule.run(&mut world);

        let intent = world.get::<MoveIntent>(player).unwrap();
        assert_eq!(intent.target, TilePosition::new(5, 4, 0));
    }

    #[test]
    fn process_input_pause_sets_paused() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::Pause,
        });

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);
        schedule.run(&mut world);

        assert_eq!(world.resource::<SimulationTime>().tick_rate, TickRate::Paused);
    }

    #[test]
    fn process_input_set_tick_rate() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::SetTickRate(TickRate::Half),
        });

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);
        schedule.run(&mut world);

        assert_eq!(world.resource::<SimulationTime>().tick_rate, TickRate::Half);
    }

    #[test]
    #[should_panic(expected = "PlayerCharacter entity must exist")]
    fn process_input_no_player_panics() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);
        schedule.run(&mut world);
    }

    #[test]
    fn process_input_future_tick_ignored() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        let player = world
            .spawn((PlayerCharacter, TilePosition::new(5, 5, 0)))
            .id();

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 5,
            action: PlayerAction::MoveNorth,
        });

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);
        schedule.run(&mut world);

        // No MoveIntent should be created (input for future tick)
        assert!(world.get::<MoveIntent>(player).is_none());
    }

    use crate::bridge::types::MovementStance;

    #[test]
    fn toggle_stance_up_changes_stance() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        world.spawn((
            PlayerCharacter,
            TilePosition::new(5, 5, 0),
            Stance::default(),
            PlayerMoveCooldown::default(),
        ));

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::ToggleStanceUp,
        });

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);
        schedule.run(&mut world);

        let mut query = world.query::<&Stance>();
        let stance = query.single(&world).unwrap();
        assert_eq!(stance.0, MovementStance::Sprint);
    }

    #[test]
    fn toggle_stance_down_changes_stance() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        world.spawn((
            PlayerCharacter,
            TilePosition::new(5, 5, 0),
            Stance::default(),
            PlayerMoveCooldown::default(),
        ));

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::ToggleStanceDown,
        });

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);
        schedule.run(&mut world);

        let mut query = world.query::<&Stance>();
        let stance = query.single(&world).unwrap();
        assert_eq!(stance.0, MovementStance::Careful);
    }

    #[test]
    fn walk_stance_throttles_movement_to_every_2_ticks() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        let player = world
            .spawn((
                PlayerCharacter,
                TilePosition::new(5, 5, 0),
                Stance::default(), // Walk
                PlayerMoveCooldown::default(),
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);

        // Tick 0: move north — should succeed (first move)
        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });
        schedule.run(&mut world);
        assert!(world.get::<MoveIntent>(player).is_some(), "first move should succeed");

        // Remove MoveIntent (simulating validate_movement consuming it)
        world.entity_mut(player).remove::<MoveIntent>();

        // Tick 0 again: move north — should be throttled (cooldown)
        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });
        schedule.run(&mut world);
        assert!(world.get::<MoveIntent>(player).is_none(), "second move should be throttled");

        // Tick 0 again: move north — should succeed (cooldown elapsed)
        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });
        schedule.run(&mut world);
        assert!(world.get::<MoveIntent>(player).is_some(), "third move should succeed after cooldown");
    }

    #[test]
    fn sprint_stance_allows_every_tick() {
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        let player = world
            .spawn((
                PlayerCharacter,
                TilePosition::new(5, 5, 0),
                Stance(MovementStance::Sprint),
                PlayerMoveCooldown::default(),
            ))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);

        // First move
        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });
        schedule.run(&mut world);
        assert!(world.get::<MoveIntent>(player).is_some());
        world.entity_mut(player).remove::<MoveIntent>();

        // Second move — sprint allows every tick
        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });
        schedule.run(&mut world);
        assert!(world.get::<MoveIntent>(player).is_some(), "sprint should allow every tick");
    }

    #[test]
    fn no_stance_component_moves_unrestricted() {
        // Backward compatibility: entities without Stance/Cooldown move freely
        let mut world = bevy_ecs::world::World::new();
        world.insert_resource(InputQueue::default());
        world.insert_resource(SimulationTime::default());

        let player = world
            .spawn((PlayerCharacter, TilePosition::new(5, 5, 0)))
            .id();

        let mut schedule = bevy_ecs::schedule::Schedule::default();
        schedule.add_systems(process_player_input);

        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });
        schedule.run(&mut world);
        assert!(world.get::<MoveIntent>(player).is_some());
        world.entity_mut(player).remove::<MoveIntent>();

        // Second move immediately — no throttle without components
        world.resource_mut::<InputQueue>().push(PlayerInput {
            tick: 0,
            action: PlayerAction::MoveNorth,
        });
        schedule.run(&mut world);
        assert!(world.get::<MoveIntent>(player).is_some());
    }
}