//! Map construction and building functionality.
use crate::constants::{MapTile, BOARD_CELL_SIZE, CELL_SIZE};
use crate::map::direction::Direction;
use crate::map::graph::{Graph, Node, TraversalFlags};
use crate::map::parser::MapTileParser;
use crate::systems::{NodeId, Position};
use bevy_ecs::resource::Resource;
use glam::{I8Vec2, IVec2, Vec2};
use std::collections::{HashMap, VecDeque};
use tracing::debug;

use crate::error::{GameResult, MapError};

/// Predefined spawn locations for all game entities within the navigation graph.
///
/// These positions are determined during map parsing and graph construction.
pub struct NodePositions {
    /// Pac-Man's starting position in the lower section of the maze
    pub pacman: NodeId,
    /// Blinky starts at the ghost house entrance
    pub blinky: NodeId,
    /// Pinky starts in the left area of the ghost house
    pub pinky: NodeId,
    /// Inky starts in the right area of the ghost house
    pub inky: NodeId,
    /// Clyde starts in the center of the ghost house
    pub clyde: NodeId,
    /// Fruit spawn location directly below the ghost house
    pub fruit_spawn: Position,
}

/// Complete maze representation combining visual layout with navigation pathfinding.
///
/// Transforms the ASCII board layout into a fully connected navigation graph
/// while preserving tile-based collision and rendering data. The graph enables
/// smooth entity movement with proper pathfinding, while the grid mapping allows
/// efficient spatial queries and debug visualization.
#[derive(Resource)]
pub struct Map {
    /// Connected graph of navigable positions.
    pub graph: Graph,
    /// Bidirectional mapping between 2D grid coordinates and graph node indices.
    pub grid_to_node: HashMap<I8Vec2, NodeId>,
    /// Predetermined spawn locations for all game entities
    pub start_positions: NodePositions,
    /// 2D array of tile types for collision detection and rendering
    tiles: [[MapTile; BOARD_CELL_SIZE.y as usize]; BOARD_CELL_SIZE.x as usize],
}

impl Map {
    /// Creates a new `Map` instance from a raw board layout.
    ///
    /// This constructor initializes the map tiles based on the provided character layout
    /// and then generates a navigation graph from the walkable areas.
    ///
    /// # Panics
    ///
    /// This function will panic if the board layout contains unknown characters or if
    /// the house door is not defined by exactly two '=' characters.
    pub fn new(raw_board: [&str; BOARD_CELL_SIZE.y as usize]) -> GameResult<Map> {
        debug!("Starting map construction from character layout");
        let parsed_map = MapTileParser::parse_board(raw_board)?;

        let map = parsed_map.tiles;
        let house_door = parsed_map.house_door;
        let tunnel_ends = parsed_map.tunnel_ends;
        debug!(
            house_door_count = house_door.len(),
            tunnel_ends_count = tunnel_ends.len(),
            "Parsed map special locations"
        );

        let mut graph = Graph::new();
        let mut grid_to_node = HashMap::new();

        let cell_offset = Vec2::splat(CELL_SIZE as f32 / 2.0);

        // Find a starting point for the graph generation, preferably Pac-Man's position.
        let start_pos = parsed_map
            .pacman_start
            .ok_or_else(|| MapError::InvalidConfig("Pac-Man's starting position not found".to_string()))?;

        // Add the starting position to the graph/queue
        let mut queue = VecDeque::new();
        queue.push_back(start_pos);
        let pos = Vec2::new(
            (start_pos.x as i32 * CELL_SIZE as i32) as f32,
            (start_pos.y as i32 * CELL_SIZE as i32) as f32,
        ) + cell_offset;
        let node_id = graph.add_node(Node { position: pos });
        grid_to_node.insert(start_pos, node_id);

        // Iterate over the queue, adding nodes to the graph and connecting them to their neighbors
        while let Some(source_position) = queue.pop_front() {
            for dir in Direction::DIRECTIONS {
                let new_position = source_position + dir.as_ivec2();

                // Skip if the new position is out of bounds
                if new_position.x < 0
                    || new_position.x as i32 >= BOARD_CELL_SIZE.x as i32
                    || new_position.y < 0
                    || new_position.y as i32 >= BOARD_CELL_SIZE.y as i32
                {
                    continue;
                }

                // Skip if the new position is already in the graph
                if grid_to_node.contains_key(&new_position) {
                    continue;
                }

                // Skip if the new position is not a walkable tile
                if matches!(
                    map[new_position.x as usize][new_position.y as usize],
                    MapTile::Pellet | MapTile::PowerPellet | MapTile::Empty | MapTile::Tunnel
                ) {
                    // Add the new position to the graph/queue
                    let pos = Vec2::new(
                        (new_position.x as i32 * CELL_SIZE as i32) as f32,
                        (new_position.y as i32 * CELL_SIZE as i32) as f32,
                    ) + cell_offset;
                    let new_node_id = graph.add_node(Node { position: pos });
                    grid_to_node.insert(new_position, new_node_id);
                    queue.push_back(new_position);

                    // Connect the new node to the source node
                    let source_node_id = grid_to_node
                        .get(&source_position)
                        .unwrap_or_else(|| panic!("Source node not found for {source_position}"));

                    // Connect the new node to the source node
                    graph
                        .connect(*source_node_id, new_node_id, false, None, dir)
                        .map_err(|e| MapError::InvalidConfig(format!("Failed to add edge: {e}")))?;
                }
            }
        }

        // While most nodes are already connected to their neighbors, some may not be, so we need to connect them
        for (grid_pos, &node_id) in &grid_to_node {
            for dir in Direction::DIRECTIONS {
                // If the node doesn't have an edge in this direction, look for a neighbor in that direction
                if graph.adjacency_list[node_id as usize].get(dir).is_none() {
                    let neighbor = grid_pos + dir.as_ivec2();
                    // If the neighbor exists, connect the node to it
                    if let Some(&neighbor_id) = grid_to_node.get(&neighbor) {
                        graph
                            .connect(node_id, neighbor_id, false, None, dir)
                            .map_err(|e| MapError::InvalidConfig(format!("Failed to add edge: {e}")))?;
                    }
                }
            }
        }

        // Build house structure
        let (house_entrance_node_id, left_center_node_id, center_center_node_id, right_center_node_id) =
            Self::build_house(&mut graph, &grid_to_node, &house_door)?;

        // Find fruit spawn location (directly below ghost house)
        let left_node_position = I8Vec2::new(13, 17);
        let left_node_id = grid_to_node.get(&left_node_position).unwrap();
        let right_node_position = I8Vec2::new(14, 17);
        let right_node_id = grid_to_node.get(&right_node_position).unwrap();

        let distance = graph
            .get_node(*right_node_id)
            .unwrap()
            .position
            .distance(graph.get_node(*left_node_id).unwrap().position);

        // interpolate between the two nodes
        let fruit_spawn_position: Position = Position::Moving {
            from: *left_node_id,
            to: *right_node_id,
            remaining_distance: distance / 2.0,
        };

        let start_positions = NodePositions {
            pacman: grid_to_node[&start_pos],
            blinky: house_entrance_node_id,
            pinky: left_center_node_id,
            inky: right_center_node_id,
            clyde: center_center_node_id,
            fruit_spawn: fruit_spawn_position,
        };

        // Build tunnel connections
        debug!("Building tunnel connections");
        Self::build_tunnels(&mut graph, &grid_to_node, &tunnel_ends)?;

        debug!(node_count = graph.nodes().count(), "Map construction completed successfully");
        Ok(Map {
            graph,
            grid_to_node,
            start_positions,
            tiles: map,
        })
    }

    pub fn iter_nodes(&self) -> impl Iterator<Item = (&NodeId, &MapTile)> {
        self.grid_to_node.iter().map(move |(pos, node_id)| {
            let tile = &self.tiles[pos.x as usize][pos.y as usize];
            (node_id, tile)
        })
    }

    /// Returns the `MapTile` at a given node id.
    pub fn tile_at_node(&self, node_id: NodeId) -> Option<MapTile> {
        // reverse lookup: node -> grid
        for (grid_pos, id) in &self.grid_to_node {
            if *id == node_id {
                return Some(self.tiles[grid_pos.x as usize][grid_pos.y as usize]);
            }
        }
        None
    }

    /// Constructs the ghost house area with restricted access and internal navigation.
    ///
    /// Creates a multi-level ghost house with entrance control, internal movement
    /// areas, and starting positions for each ghost. The house entrance uses
    /// ghost-only traversal flags to prevent Pac-Man from entering while allowing
    /// ghosts to exit. Internal nodes are arranged in vertical lines to provide
    /// distinct starting areas for each ghost character.
    ///
    /// # Returns
    ///
    /// Tuple of node IDs: (house_entrance, left_center, center_center, right_center)
    /// representing the four key positions within the ghost house structure.
    fn build_house(
        graph: &mut Graph,
        grid_to_node: &HashMap<I8Vec2, NodeId>,
        house_door: &[Option<I8Vec2>; 2],
    ) -> GameResult<(NodeId, NodeId, NodeId, NodeId)> {
        // Calculate the position of the house entrance node
        let (house_entrance_node_id, house_entrance_node_position) = {
            // Translate the grid positions to the actual node ids
            let left_node = grid_to_node
                .get(
                    &(house_door[0]
                        .ok_or_else(|| MapError::InvalidConfig("First house door position not acquired".to_string()))?
                        + Direction::Left.as_ivec2()),
                )
                .ok_or_else(|| MapError::InvalidConfig("Left house door node not found".to_string()))?;
            let right_node = grid_to_node
                .get(
                    &(house_door[1]
                        .ok_or_else(|| MapError::InvalidConfig("Second house door position not acquired".to_string()))?
                        + Direction::Right.as_ivec2()),
                )
                .ok_or_else(|| MapError::InvalidConfig("Right house door node not found".to_string()))?;

            // Calculate the position of the house node
            let (node_id, node_position) = {
                let left_pos = graph
                    .get_node(*left_node)
                    .ok_or(MapError::NodeNotFound(*left_node as usize))?
                    .position;
                let right_pos = graph
                    .get_node(*right_node)
                    .ok_or(MapError::NodeNotFound(*right_node as usize))?
                    .position;
                let house_node = graph.add_node(Node {
                    position: left_pos.lerp(right_pos, 0.5),
                });
                (house_node, left_pos.lerp(right_pos, 0.5))
            };

            // Connect the house door to the left and right nodes
            graph
                .connect(node_id, *left_node, true, None, Direction::Left)
                .map_err(|e| MapError::InvalidConfig(format!("Failed to connect house door to left node: {e}")))?;
            graph
                .connect(node_id, *right_node, true, None, Direction::Right)
                .map_err(|e| MapError::InvalidConfig(format!("Failed to connect house door to right node: {e}")))?;

            (node_id, node_position)
        };

        // A helper function to help create the various 'lines' of nodes within the house
        let create_house_line = |graph: &mut Graph, center_pos: Vec2| -> GameResult<(NodeId, NodeId)> {
            // Place the nodes at, above, and below the center position
            let center_node_id = graph.add_node(Node { position: center_pos });
            let top_node_id = graph.add_node(Node {
                position: center_pos + IVec2::from(Direction::Up.as_ivec2()).as_vec2() * (CELL_SIZE as f32 / 2.0),
            });
            let bottom_node_id = graph.add_node(Node {
                position: center_pos + IVec2::from(Direction::Down.as_ivec2()).as_vec2() * (CELL_SIZE as f32 / 2.0),
            });

            // Connect the center node to the top and bottom nodes
            graph
                .connect(center_node_id, top_node_id, false, None, Direction::Up)
                .map_err(|e| MapError::InvalidConfig(format!("Failed to connect house line to top node: {e}")))?;
            graph
                .connect(center_node_id, bottom_node_id, false, None, Direction::Down)
                .map_err(|e| MapError::InvalidConfig(format!("Failed to connect house line to bottom node: {e}")))?;

            Ok((center_node_id, top_node_id))
        };

        // Calculate the position of the center line's center node
        let center_line_center_position =
            house_entrance_node_position + IVec2::from(Direction::Down.as_ivec2()).as_vec2() * (3.0 * CELL_SIZE as f32);

        // Create the center line
        let (center_center_node_id, center_top_node_id) = create_house_line(graph, center_line_center_position)?;

        // Create a ghost-only, two-way connection for the house door.
        // This prevents Pac-Man from entering or exiting through the door.
        graph
            .add_edge(
                house_entrance_node_id,
                center_top_node_id,
                false,
                None,
                Direction::Down,
                TraversalFlags::GHOST,
            )
            .map_err(|e| MapError::InvalidConfig(format!("Failed to create ghost-only entrance to house: {e}")))?;

        graph
            .add_edge(
                center_top_node_id,
                house_entrance_node_id,
                false,
                None,
                Direction::Up,
                TraversalFlags::GHOST,
            )
            .map_err(|e| MapError::InvalidConfig(format!("Failed to create ghost-only exit from house: {e}")))?;

        // Create the left line
        let (left_center_node_id, _) = create_house_line(
            graph,
            center_line_center_position + IVec2::from(Direction::Left.as_ivec2()).as_vec2() * (CELL_SIZE as f32 * 2.0),
        )?;

        // Create the right line
        let (right_center_node_id, _) = create_house_line(
            graph,
            center_line_center_position + IVec2::from(Direction::Right.as_ivec2()).as_vec2() * (CELL_SIZE as f32 * 2.0),
        )?;

        debug!("Left center node id: {left_center_node_id}");

        // Connect the center line to the left and right lines
        graph
            .connect(center_center_node_id, left_center_node_id, false, None, Direction::Left)
            .map_err(|e| MapError::InvalidConfig(format!("Failed to connect house entrance to left top line: {e}")))?;

        graph
            .connect(center_center_node_id, right_center_node_id, false, None, Direction::Right)
            .map_err(|e| MapError::InvalidConfig(format!("Failed to connect house entrance to right top line: {e}")))?;

        debug!("House entrance node id: {house_entrance_node_id}");

        Ok((
            house_entrance_node_id,
            left_center_node_id,
            center_center_node_id,
            right_center_node_id,
        ))
    }

    /// Creates horizontal tunnel portals for instant teleportation across the maze.
    ///
    /// Establishes the tunnel system that allows entities to instantly travel from the left edge of the maze to the right edge.
    /// Creates hidden intermediate nodes beyond the visible tunnel entrances and connects them with zero-distance edges for instantaneous traversal.
    fn build_tunnels(
        graph: &mut Graph,
        grid_to_node: &HashMap<I8Vec2, NodeId>,
        tunnel_ends: &[Option<I8Vec2>; 2],
    ) -> GameResult<()> {
        // Create the hidden tunnel nodes
        let left_tunnel_hidden_node_id = {
            let left_tunnel_entrance_node_id =
                grid_to_node[&tunnel_ends[0].ok_or_else(|| MapError::InvalidConfig("Left tunnel end not found".to_string()))?];
            let left_tunnel_entrance_node = graph
                .get_node(left_tunnel_entrance_node_id)
                .ok_or_else(|| MapError::InvalidConfig("Left tunnel entrance node not found".to_string()))?;

            graph
                .add_connected(
                    left_tunnel_entrance_node_id,
                    Direction::Left,
                    Node {
                        position: left_tunnel_entrance_node.position
                            + IVec2::from(Direction::Left.as_ivec2()).as_vec2() * (CELL_SIZE as f32 * 2.0),
                    },
                )
                .expect("Failed to connect left tunnel entrance to left tunnel hidden node")
        };

        // Create the right tunnel nodes
        let right_tunnel_hidden_node_id = {
            let right_tunnel_entrance_node_id =
                grid_to_node[&tunnel_ends[1].ok_or_else(|| MapError::InvalidConfig("Right tunnel end not found".to_string()))?];
            let right_tunnel_entrance_node = graph
                .get_node(right_tunnel_entrance_node_id)
                .ok_or_else(|| MapError::InvalidConfig("Right tunnel entrance node not found".to_string()))?;

            graph
                .add_connected(
                    right_tunnel_entrance_node_id,
                    Direction::Right,
                    Node {
                        position: right_tunnel_entrance_node.position
                            + IVec2::from(Direction::Right.as_ivec2()).as_vec2() * (CELL_SIZE as f32 * 2.0),
                    },
                )
                .expect("Failed to connect right tunnel entrance to right tunnel hidden node")
        };

        // Connect the left tunnel hidden node to the right tunnel hidden node
        graph
            .connect(
                left_tunnel_hidden_node_id,
                right_tunnel_hidden_node_id,
                false,
                Some(0.0),
                Direction::Left,
            )
            .expect("Failed to connect left tunnel hidden node to right tunnel hidden node");

        Ok(())
    }
}