use bevy_ecs::prelude::Resource;
use glam::UVec2;
use image::GenericImageView;
use serde::{Deserialize, Serialize};
use std::fs;
use tracing::{debug, info};

use crate::game::territory::get_idx;
use crate::game::tilemap::TileMap;

/// Calculate terrain color using pastel theme formulas
fn calculate_theme_color(color_base: &str, color_variant: u8) -> [u8; 3] {
    let i = color_variant as i32;

    match color_base {
        "grass" => {
            // rgb(238 - 2 * i, 238 - 2 * i, 190 - i)
            [(238 - 2 * i).clamp(0, 255) as u8, (238 - 2 * i).clamp(0, 255) as u8, (190 - i).clamp(0, 255) as u8]
        }
        "mountain" => {
            // rgb(250 - 2 * i, 250 - 2 * i, 220 - i)
            [(250 - 2 * i).clamp(0, 255) as u8, (250 - 2 * i).clamp(0, 255) as u8, (220 - i).clamp(0, 255) as u8]
        }
        "water" => {
            // rgb(172 - 2 * i, 225 - 2 * i, 249 - 3 * i)
            [(172 - 2 * i).clamp(0, 255) as u8, (225 - 2 * i).clamp(0, 255) as u8, (249 - 3 * i).clamp(0, 255) as u8]
        }
        _ => {
            // Default fallback color (gray)
            [128, 128, 128]
        }
    }
}

/// Helper structs for loading World.json format
#[derive(Deserialize)]
struct WorldMapJson {
    tiles: Vec<WorldTileDef>,
}

#[derive(Deserialize)]
struct WorldTileDef {
    color: String,
    name: String,
    #[serde(default, rename = "colorBase")]
    color_base: Option<String>,
    #[serde(default, rename = "colorVariant")]
    color_variant: Option<u32>,
    conquerable: bool,
    navigable: bool,
    #[serde(default, rename = "expansionCost")]
    expansion_cost: Option<u32>,
    #[serde(default, rename = "expansionTime")]
    expansion_time: Option<u32>,
}

/// Parse hex color string (#RRGGBB) to RGB bytes
fn parse_hex_rgb(s: &str) -> Option<[u8; 3]> {
    let s = s.trim_start_matches('#');
    if s.len() != 6 {
        return None;
    }
    let r = u8::from_str_radix(&s[0..2], 16).ok()?;
    let g = u8::from_str_radix(&s[2..4], 16).ok()?;
    let b = u8::from_str_radix(&s[4..6], 16).ok()?;
    Some([r, g, b])
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TileType {
    pub name: String,
    pub color_base: String,
    pub color_variant: u8,
    pub conquerable: bool,
    pub navigable: bool,
    pub expansion_time: u8,
    pub expansion_cost: u8,
}

/// Map manifest structure
#[derive(Debug, Clone, Deserialize, Serialize)]
pub struct MapManifest {
    pub map: MapMetadata,
    pub name: String,
    pub nations: Vec<NationSpawn>,
}

/// Map size metadata
#[derive(Debug, Clone, Deserialize, Serialize)]
pub struct MapMetadata {
    pub width: usize,
    pub height: usize,
    pub num_land_tiles: usize,
}

/// Nation spawn point
#[derive(Debug, Clone, Deserialize, Serialize)]
pub struct NationSpawn {
    pub coordinates: [usize; 2],
    pub flag: String,
    pub name: String,
    pub strength: u32,
}

/// Loaded map data
#[derive(Debug, Clone, Resource)]
pub struct TerrainData {
    pub _manifest: MapManifest,
    /// Legacy terrain data (for backward compatibility)
    pub terrain_data: TileMap<u8>,
    /// Tile type indices (new format)
    pub tiles: Vec<u8>,
    /// Tile type definitions
    pub tile_types: Vec<TileType>,
}

impl TerrainData {
    /// Load the World map from embedded assets
    pub fn load_world_map() -> Result<Self, Box<dyn std::error::Error>> {
        const MAP_JSON: &[u8] = include_bytes!("../../assets/maps/World.json");
        const MAP_PNG: &[u8] = include_bytes!("../../assets/maps/World.png");

        // Parse JSON tile definitions
        let map_json: WorldMapJson = serde_json::from_slice(MAP_JSON)?;

        // Load PNG image
        let png = image::load_from_memory(MAP_PNG)?;
        let (width, height) = png.dimensions();

        info!("Loading World map: {}x{}", width, height);

        // Build color-to-index lookup table
        let color_to_index: Vec<([u8; 3], usize)> = map_json.tiles.iter().enumerate().filter_map(|(idx, t)| parse_hex_rgb(&t.color).map(|rgb| (rgb, idx))).collect();

        let mut tiles = vec![0u8; (width * height) as usize];
        let mut terrain_data_raw = vec![0u8; (width * height) as usize];

        // Match each pixel to nearest tile type by color
        for y in 0..height {
            for x in 0..width {
                let pixel = png.get_pixel(x, y).0;
                let rgb = [pixel[0], pixel[1], pixel[2]];

                // Find nearest tile by RGB distance
                let (tile_idx, _) = color_to_index
                    .iter()
                    .map(|(c, idx)| {
                        let dr = rgb[0] as i32 - c[0] as i32;
                        let dg = rgb[1] as i32 - c[1] as i32;
                        let db = rgb[2] as i32 - c[2] as i32;
                        let dist = (dr * dr + dg * dg + db * db) as u32;
                        (idx, dist)
                    })
                    .min_by_key(|(_, d)| *d)
                    .unwrap();

                let i = (y * width + x) as usize;
                tiles[i] = *tile_idx as u8;

                // Set bit 7 if conquerable (land)
                if map_json.tiles[*tile_idx].conquerable {
                    terrain_data_raw[i] |= 0x80;
                }
                // Lower 5 bits for terrain magnitude (unused for World map)
            }
        }

        // Convert to TileType format
        let tile_types = map_json.tiles.into_iter().map(|t| TileType { name: t.name, color_base: t.color_base.unwrap_or_default(), color_variant: t.color_variant.unwrap_or(0) as u8, conquerable: t.conquerable, navigable: t.navigable, expansion_cost: t.expansion_cost.unwrap_or(50) as u8, expansion_time: t.expansion_time.unwrap_or(50) as u8 }).collect();

        let num_land_tiles = terrain_data_raw.iter().filter(|&&b| b & 0x80 != 0).count();

        info!("World map loaded: {} land tiles", num_land_tiles);

        Ok(Self { _manifest: MapManifest { name: "World".to_string(), map: MapMetadata { width: width as usize, height: height as usize, num_land_tiles }, nations: vec![] }, terrain_data: TileMap::from_vec(width, height, terrain_data_raw), tiles, tile_types })
    }

    /// Load a map from the resources directory
    pub fn load(map_name: &str) -> Result<Self, Box<dyn std::error::Error>> {
        let base_path = format!("resources/maps/{}", map_name);

        // Load manifest
        let manifest_path = format!("{}/manifest.json", base_path);
        let manifest_json = fs::read_to_string(&manifest_path)?;
        let manifest: MapManifest = serde_json::from_str(&manifest_json)?;

        // Load binary map data
        let map_path = format!("{}/map.bin", base_path);
        let terrain_data_raw = fs::read(&map_path)?;

        let width = manifest.map.width as u32;
        let height = manifest.map.height as u32;

        // Verify data size
        if terrain_data_raw.len() != (width * height) as usize {
            return Err(format!("Map data size mismatch: expected {} bytes, got {}", width * height, terrain_data_raw.len()).into());
        }

        info!("Loaded map '{}' ({}x{})", manifest.name, width, height);
        debug!("Land tiles: {}/{}", manifest.map.num_land_tiles, width * height);

        // Create default tile types for legacy format
        let tile_types = vec![TileType { name: "water".to_string(), color_base: "water".to_string(), color_variant: 0, conquerable: false, navigable: true, expansion_time: 255, expansion_cost: 255 }, TileType { name: "land".to_string(), color_base: "grass".to_string(), color_variant: 0, conquerable: true, navigable: false, expansion_time: 50, expansion_cost: 50 }];

        // Convert legacy format to tile indices
        let tiles: Vec<u8> = terrain_data_raw.iter().map(|&byte| if byte & 0x80 != 0 { 1 } else { 0 }).collect();

        // Create TileMap from terrain data
        let terrain_data = TileMap::from_vec(width, height, terrain_data_raw);

        Ok(Self { _manifest: manifest, terrain_data, tiles, tile_types })
    }

    /// Get the size of the map
    pub fn size(&self) -> UVec2 {
        UVec2::new(self.terrain_data.width(), self.terrain_data.height())
    }

    pub fn get_value<T: Into<UVec2>>(&self, pos: T) -> u8 {
        self.terrain_data[get_idx(pos, self.terrain_data.width())]
    }

    /// Check if a tile is land (bit 7 set)
    pub fn is_land<T: Into<UVec2>>(&self, pos: T) -> bool {
        self.get_value(pos) & 0x80 != 0
    }

    /// Get terrain magnitude (bits 0-4)
    pub fn terrain_magnitude<T: Into<UVec2>>(&self, pos: T) -> u8 {
        self.get_value(pos) & 0b00011111
    }

    /// Get tile type at position
    pub fn get_tile_type<T: Into<UVec2>>(&self, pos: T) -> &TileType {
        let idx = get_idx(pos, self.terrain_data.width());
        &self.tile_types[self.tiles[idx] as usize]
    }

    /// Check if a tile is conquerable
    pub fn is_conquerable<T: Into<UVec2>>(&self, pos: T) -> bool {
        self.get_tile_type(pos).conquerable
    }

    /// Check if a tile is navigable (water)
    pub fn is_navigable<T: Into<UVec2>>(&self, pos: T) -> bool {
        self.get_tile_type(pos).navigable
    }

    /// Get expansion time for a tile
    pub fn get_expansion_time<T: Into<UVec2>>(&self, pos: T) -> u8 {
        self.get_tile_type(pos).expansion_time
    }

    /// Get expansion cost for a tile
    pub fn get_expansion_cost<T: Into<UVec2>>(&self, pos: T) -> u8 {
        self.get_tile_type(pos).expansion_cost
    }

    /// Get tile type IDs for rendering (each position maps to a tile type)
    pub fn get_tile_ids(&self) -> &[u8] {
        &self.tiles
    }

    /// Get terrain palette colors from tile types (for rendering)
    /// Returns a vec where index = tile type ID, value = RGB color
    /// Colors are calculated using theme formulas based on colorBase and colorVariant
    pub fn get_terrain_palette_colors(&self) -> Vec<[u8; 3]> {
        self.tile_types.iter().map(|tile_type| calculate_theme_color(&tile_type.color_base, tile_type.color_variant)).collect()
    }
}