use crate::game::{Archetype, Board, FontSpec, Glyph, ObjectDef, Player, PortalDef};
use eframe::egui::Color32;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::convert::TryFrom;
use std::path::Path;

/// The top-level serialization/deserialization type for a `.toml` map file.
///
/// This struct mirrors the TOML file structure exactly. On load it is
/// immediately converted into a [`Board`] via [`TryFrom<MapFile>`] and then
/// discarded. On save a [`Board`] is converted back into this struct via
/// [`From<&Board>`] before serialization.
///
/// See `maps/start.toml` for a complete example of the file format.
#[derive(Deserialize, Serialize)]
pub struct MapFile {
    /// The `[map]` section: name, dimensions, player start position.
    pub map: MapHeader,
    /// The `[palette]` section: maps single-character keys to tile definitions.
    pub palette: HashMap<String, PaletteEntry>,
    /// The `[grid]` section: the multi-line string that defines cell layout.
    pub grid: GridData,
    /// Optional `[font]` section specifying a bitmap font for this board.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub font: Option<FontHeader>,
    /// Any `[[objects]]` entries. Optional; defaults to empty.
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub objects: Vec<ObjectDef>,
    /// Any `[[portals]]` entries. Optional; defaults to empty.
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub portals: Vec<PortalDef>,
    /// The `[scripts]` table: maps script names to Rhai source text.
    /// Optional; defaults to empty.
    #[serde(default, skip_serializing_if = "HashMap::is_empty")]
    pub scripts: HashMap<String, String>,
}

/// The `[map]` header section of a map file.
#[derive(Deserialize, Serialize)]
pub struct MapHeader {
    /// Human-readable name for this board, e.g. `"Opening Room"`.
    pub name: String,
    /// Width of the board in cells. Must match the length of every row in `[grid] content`.
    pub width: usize,
    /// Height of the board in cells. Must match the number of rows in `[grid] content`.
    pub height: usize,
    /// Starting position of the player as `[x, y]` (0-indexed, origin top-left).
    pub player_start: [i32; 2],
    /// Name of the board-level script in the `[scripts]` table, if any.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub board_script_name: Option<String>,
}

/// The `[font]` section of a map file, specifying a bitmap font for this board.
///
/// When absent, the app's default embedded CP437 font is used.
#[derive(Deserialize, Serialize)]
pub struct FontHeader {
    /// Path to the PNG font image, relative to the working directory.
    pub path: String,
    /// Width of each tile in the font image, in pixels.
    pub tile_w: u32,
    /// Height of each tile in the font image, in pixels.
    pub tile_h: u32,
}

/// A tile index in a palette entry: either a plain integer or a character literal.
///
/// Accepting both forms lets map files use `tile = 32` for new files or
/// `tile = " "` for convenience (the char is converted to its Unicode scalar).
/// This means existing maps that used `ch = "#"` can be migrated by renaming
/// the key to `tile`; the char form keeps working.
#[derive(Deserialize, Serialize)]
#[serde(untagged)]
enum TileIndex {
    /// A direct tile index (e.g. `tile = 35`).
    Num(u32),
    /// A single-character shorthand (e.g. `tile = "#"`); converted to its Unicode scalar.
    Chr(char),
}

impl TileIndex {
    fn into_u32(self) -> u32 {
        match self {
            TileIndex::Num(n) => n,
            TileIndex::Chr(c) => c as u32,
        }
    }
}

/// One entry in the `[palette]` table.
///
/// Each entry is keyed by a single character (e.g. `"#"` or `" "`).
/// That character is used in the `[grid]` content string to place tiles.
/// The entry defines both how the tile looks (`tile`, `fg`, `bg`) and which
/// [`Archetype`] it uses for behavior.
///
/// `tile` accepts either an integer (`tile = 35`) or a char (`tile = "#"`).
#[derive(Deserialize, Serialize)]
pub struct PaletteEntry {
    /// The archetype name for this tile, e.g. `"wall"` or `"empty"`.
    pub archetype: String,
    /// The tile index into the board's bitmap font.
    /// Accepts either an integer or a single-character string.
    tile: TileIndex,
    /// Foreground color as an `"#RRGGBB"` hex string.
    pub fg: String,
    /// Background color as an `"#RRGGBB"` hex string.
    pub bg: String,
}

/// The `[grid]` section of a map file.
///
/// `content` is a TOML multi-line string. Each line is one row of the board;
/// each character in a line is looked up in the palette to determine the
/// tile for that cell.
#[derive(Deserialize, Serialize)]
pub struct GridData {
    /// The raw grid content. Split by [`str::lines`] during loading.
    pub content: String,
}

/// Parses an `"#RRGGBB"` hex color string into a [`Color32`].
/// Returns black on any parse failure.
fn parse_color(hex: &str) -> Color32 {
    let hex = hex.trim_start_matches('#');
    if hex.len() != 6 {
        return Color32::BLACK;
    }
    let r = u8::from_str_radix(&hex[0..2], 16).unwrap_or(0);
    let g = u8::from_str_radix(&hex[2..4], 16).unwrap_or(0);
    let b = u8::from_str_radix(&hex[4..6], 16).unwrap_or(0);
    Color32::from_rgb(r, g, b)
}

/// Converts a [`Color32`] to an `"#RRGGBB"` hex string.
fn color_to_hex(color: Color32) -> String {
    format!("#{:02X}{:02X}{:02X}", color.r(), color.g(), color.b())
}

/// Converts a parsed map file into a runtime [`Board`].
///
/// Returns `Err(String)` if the grid dimensions do not match the header:
/// - wrong number of rows (actual row count ≠ `height`)
/// - any row whose character count ≠ `width`
///
/// The conversion proceeds in two passes:
///
/// 1. **Palette pass** — each entry is parsed into a `(Glyph, Archetype)` pair
///    and stored in a temporary `HashMap` keyed by the palette character.
///    Unknown archetype names produce an [`Archetype::ErrorBlock`] and a logged
///    warning so malformed maps are visible in-game.
///
/// 2. **Grid pass** — `grid.content` is split into lines; each character is
///    looked up in the palette map and pushed directly into `cells`.
impl TryFrom<MapFile> for Board {
    type Error = String;

    fn try_from(mf: MapFile) -> Result<Self, Self::Error> {
        let w = mf.map.width;
        let h = mf.map.height;

        // Pass 1: build a char → (Glyph, Archetype) lookup from the palette.
        let mut palette: HashMap<char, (Glyph, Archetype)> = HashMap::new();

        for (key, entry) in mf.palette {
            let key_char = key.chars().next().unwrap_or(' ');
            let tile = entry.tile.into_u32();
            match Archetype::try_from(entry.archetype.as_str()) {
                Ok(archetype) => {
                    let glyph = Glyph {
                        tile,
                        fg: parse_color(&entry.fg),
                        bg: parse_color(&entry.bg),
                    };
                    palette.insert(key_char, (glyph, archetype));
                }
                Err(e) => {
                    eprintln!("{e}");
                    palette.insert(
                        key_char,
                        (Archetype::ErrorBlock.default_glyph(), Archetype::ErrorBlock),
                    );
                }
            }
        }

        // Validate grid dimensions before walking cells.
        // Collect lines eagerly so we can check the count and reuse them.
        let rows: Vec<&str> = mf.grid.content.lines().collect();
        if rows.len() != h {
            return Err(format!(
                "grid has {} rows but map header declares height = {}",
                rows.len(),
                h
            ));
        }
        for (i, line) in rows.iter().enumerate() {
            let col_count = line.chars().count();
            if col_count != w {
                return Err(format!(
                    "grid row {} has {} characters but map header declares width = {}",
                    i, col_count, w
                ));
            }
        }

        // Pass 2: walk the validated grid and build cells.
        let mut cells: Vec<(Glyph, Archetype)> = Vec::with_capacity(w * h);
        for line in &rows {
            for ch in line.chars() {
                if let Some(&cell) = palette.get(&ch) {
                    cells.push(cell);
                }
            }
        }

        let font = mf.font.map(|f| FontSpec {
            path: f.path,
            tile_w: f.tile_w,
            tile_h: f.tile_h,
        });

        Ok(Board {
            name: mf.map.name,
            width: w,
            height: h,
            cells,
            player: Player {
                x: mf.map.player_start[0],
                y: mf.map.player_start[1],
            },
            objects: mf.objects,
            portals: mf.portals,
            font,
            scripts: mf.scripts,
            board_script_name: mf.map.board_script_name,
        })
    }
}

/// Converts a runtime [`Board`] back into a serializable [`MapFile`].
///
/// The palette is reconstructed by enumerating unique `(Glyph, Archetype)`
/// combinations in the board's cells and assigning each a single printable
/// ASCII character key. The grid is rebuilt by looking up each cell in the
/// resulting palette map.
impl From<&Board> for MapFile {
    fn from(board: &Board) -> Self {
        // Pool for non-empty archetypes: printable ASCII 33-126 ('!' onward),
        // excluding `"` and `\` which would require escaping inside TOML strings.
        // Space (32) is reserved exclusively for Archetype::Empty.
        let pool: Vec<char> = (33u8..=126u8)
            .filter(|&b| b != b'"' && b != b'\\')
            .map(|b| b as char)
            .collect();
        let mut pool_iter = pool.iter();

        // The canonical empty cell (tile 32, black/black) is always serialized as ' '.
        // Every other unique (Glyph, Archetype) pair draws from the pool above.
        let canonical_empty = (Archetype::Empty.default_glyph(), Archetype::Empty);
        let mut cell_to_key: HashMap<(Glyph, Archetype), char> = HashMap::new();
        let mut palette: HashMap<String, PaletteEntry> = HashMap::new();

        for y in 0..board.height {
            for x in 0..board.width {
                let (glyph, arch) = board.get(x, y);
                let key = (*glyph, *arch);
                if !cell_to_key.contains_key(&key) {
                    if key == canonical_empty {
                        cell_to_key.insert(key, ' ');
                        palette.insert(
                            " ".to_string(),
                            PaletteEntry {
                                archetype: arch.name().to_string(),
                                tile: TileIndex::Num(glyph.tile),
                                fg: color_to_hex(glyph.fg),
                                bg: color_to_hex(glyph.bg),
                            },
                        );
                    } else {
                        let ch = *pool_iter
                            .next()
                            .expect("board has more than 92 unique non-canonical cell types");
                        cell_to_key.insert(key, ch);
                        palette.insert(
                            ch.to_string(),
                            PaletteEntry {
                                archetype: arch.name().to_string(),
                                tile: TileIndex::Num(glyph.tile),
                                fg: color_to_hex(glyph.fg),
                                bg: color_to_hex(glyph.bg),
                            },
                        );
                    }
                }
            }
        }

        // Pass 2: reconstruct the grid string row by row.
        let mut rows: Vec<String> = Vec::with_capacity(board.height);
        for y in 0..board.height {
            let mut row = String::with_capacity(board.width);
            for x in 0..board.width {
                let (glyph, arch) = board.get(x, y);
                row.push(cell_to_key[&(*glyph, *arch)]);
            }
            rows.push(row);
        }
        // Trailing newline ensures the last row is complete; str::lines handles it correctly.
        let content = rows.join("\n") + "\n";

        let font = board.font.as_ref().map(|f| FontHeader {
            path: f.path.clone(),
            tile_w: f.tile_w,
            tile_h: f.tile_h,
        });

        // Reconstruct objects as plain structs (ObjectDef/PortalDef don't implement Clone).
        let objects = board
            .objects
            .iter()
            .map(|o| ObjectDef {
                x: o.x,
                y: o.y,
                script_name: o.script_name.clone(),
            })
            .collect();
        let portals = board
            .portals
            .iter()
            .map(|p| PortalDef {
                x: p.x,
                y: p.y,
                target_map: p.target_map.clone(),
                target_entry: p.target_entry.clone(),
            })
            .collect();

        MapFile {
            map: MapHeader {
                name: board.name.clone(),
                width: board.width,
                height: board.height,
                player_start: [board.player.x, board.player.y],
                board_script_name: board.board_script_name.clone(),
            },
            palette,
            grid: GridData { content },
            font,
            objects,
            portals,
            scripts: board.scripts.clone(),
        }
    }
}

/// Loads a map file from disk and returns a ready-to-use [`Board`].
///
/// Reads the file at `path`, deserializes it as TOML into a [`MapFile`],
/// then converts it via [`TryFrom<MapFile>`]. Propagates I/O errors, TOML
/// parse errors, and grid dimension mismatches through the `Box<dyn Error>` return.
pub fn load(path: &str) -> Result<Board, Box<dyn std::error::Error>> {
    let content = std::fs::read_to_string(path)?;
    let map_file: MapFile = toml::from_str(&content)?;
    Board::try_from(map_file).map_err(|e| e.into())
}

/// Serializes a [`Board`] to a `.toml` map file at `path`.
///
/// Converts the board to a [`MapFile`] via [`From<&Board>`], then serializes
/// it with `toml::to_string_pretty`. Propagates I/O and serialization errors.
pub fn save(board: &Board, path: &Path) -> Result<(), Box<dyn std::error::Error>> {
    let map_file = MapFile::from(board);
    let toml_str = toml::to_string_pretty(&map_file)?;
    std::fs::write(path, toml_str)?;
    Ok(())
}

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

    /// Minimal valid TOML with a configurable grid, used as a base for dimension tests.
    fn minimal_toml(width: usize, height: usize, grid_rows: &[&str]) -> String {
        let content = grid_rows.join("\n");
        // Use r##"..."## so the "# in color strings does not close the raw string.
        format!(
            r##"
[map]
name = "Test"
width = {width}
height = {height}
player_start = [0, 0]

[palette]
"." = {{ archetype = "empty", tile = 46, fg = "#000000", bg = "#000000" }}

[grid]
content = """
{content}
"""
"##
        )
    }

    #[test]
    fn grid_wrong_row_count_returns_error() {
        // height = 3 but only 2 rows in the grid
        let toml = minimal_toml(3, 3, &["...", "..."]);
        let mf: MapFile = toml::from_str(&toml).unwrap();
        let result = Board::try_from(mf);
        assert!(result.is_err());
        // Use .err().unwrap() instead of .unwrap_err() to avoid requiring Board: Debug.
        let msg = result.err().unwrap();
        assert!(msg.contains("2 rows"), "expected row count in error, got: {msg}");
        assert!(msg.contains("height = 3"), "expected declared height in error, got: {msg}");
    }

    #[test]
    fn grid_wrong_row_width_returns_error() {
        // width = 4 but second row is only 3 characters
        let toml = minimal_toml(4, 2, &["....", "..."]);
        let mf: MapFile = toml::from_str(&toml).unwrap();
        let result = Board::try_from(mf);
        assert!(result.is_err());
        let msg = result.err().unwrap();
        assert!(msg.contains("3 characters"), "expected col count in error, got: {msg}");
        assert!(msg.contains("width = 4"), "expected declared width in error, got: {msg}");
    }
}