use std::collections::{HashMap, HashSet};
use serde::{Deserialize, Serialize};
use crate::api::queue::ObjQueue;
use crate::{Builtin, Direction};
use crate::builtin::BUILTIN_SOURCES;
use crate::floor::{Floor, FloorBiome};
use crate::glyph::Glyph;
use crate::object_def::ObjectDef;
use crate::utils::{ObjectId, Pushable};
use crate::utils::Pushable::No;

/// The various ways that a tile might respond to another tile trying to move on top of it
#[derive(Serialize, Deserialize, PartialEq, Copy, Clone, Debug)]
#[serde(rename_all = "lowercase")]
pub enum EnterResponse {
    /// Flat denial: don't let the move happen, block it.
    Block,
    /// If the player moves, call the `grab` hook and then remove this object. Anything else, act as
    /// `Pushable::Any`.
    /// TODO will do something different once inventory exists as a concept
    Grab,
    /// Attempt to exit the cell ourselves, the opposite direction. This of course recurses; if our move
    /// is denied then this is the same as a block.
    Push(Pushable),
    /// Call an `enter` hook and do something. The hook is responsible for resolving the conflict:
    /// placing the moving-object somewhere else, moving ourselves somewhere else, or whatever.
    /// It should return `true` or `false`: this return value is passed back up a `Push` chain to
    /// the original moving object, determining whether the moves should happen.
    /// Example: a teleporter moves anything that enters it to another spot, if it's unblocked. It
    /// will check if the target cell is open and move the object there if it is, returning true.
    /// If you push a crate into it, it returning true means you should move (into the space the crate
    /// left behind); it returning false means the crate wasn't teleported so your move is blocked
    /// also.
    /// The hook return value is only used for _other_ things in the chain: regardless of what's returned,
    /// the engine won't touch the crate or the teleporter; the hook is responsible for handling the
    /// actual collision. A teleporter that teleports the crate and returns false will leave an empty
    /// space behind (the player won't move into it because it returned false); a teleporter that
    /// returns true without teleporting the crate, the crate will be destroyed by the player moving
    /// on top of it.
    Hook,
    /// Swap places with whatever moved on top of you, as long as it was the player. Anything else,
    /// act as `Pushable::Any`.
    Swap,
    /// Get overwritten and destroyed by whatever moved on top of us. Right now, equivalent to `Grab`
    /// if the hook does nothing (but in the future `Grab` will have other builtin behavior)
    Squish
}

impl EnterResponse {
    /// Returns whether this object will transmit a push of the given direction through it:
    /// - `Push(p)`, if p allows that direction
    /// - `Grab`, because grabbable things act like push if something pushes them
    /// - `Swap`, same reason
    pub fn transmits_push(self, dir: Direction) -> bool {
        match self {
            EnterResponse::Grab | EnterResponse::Swap => true,
            EnterResponse::Push(p) if p.allows(dir) => true,
            _ => false
        }
    }

    /// Returns whether this object will sense a bump from the given direction:
    /// - `Push(p)`, if p disallows that direction
    /// - `Block`, because nothing can move through it
    /// - `Hook`, because it's obligated to handle the entry and not pass it on
    /// - but nothing else
    pub fn bumpable(self, dir: Direction) -> bool {
        match self {
            EnterResponse::Block | EnterResponse::Hook => true,
            EnterResponse::Push(p) if !p.allows(dir) => true,
            _ => false
        }
    }
}

/// Where `Sensor`s are drawn, in relation to the grid:
/// - `Above` is above everything, including the player. If the glyph has a nonzero tile, and it's
///   visible / lit, it will be drawn.
/// - `Below` is below the grid but above the floor. A nonzero-tile-glyph will be drawn only if
///   there's not a grid-thing in the same cell.
#[derive(Serialize, Deserialize, PartialEq, Copy, Clone, Debug)]
#[serde(rename = "lowercase")]
pub enum DrawLayer { Above, Below }

/// How a thing interacts with the lighting and visibility models
#[derive(Serialize, Deserialize, PartialEq, Copy, Clone, Debug)]
#[serde(rename = "lowercase")]
pub struct Optics {
    /// Opaque things block field of view
    #[serde(default = "default_as_true")]
    pub opaque: bool,
    /// The brightness (in number of cells' radius) of light this
    /// emits. It will emit light in the color of the foreground of its glyph.
    /// A cell is visible if:
    /// - the level isn't dark, in which case lighting isn't calculated
    /// - the cell is within the field of view
    /// - the cell is within the glow radius of at least one light source
    ///
    /// Its color will be tinted by the light sources illuminating it.
    #[serde(default)]
    pub glow: u32,
}

impl Default for Optics {
    fn default() -> Self {
        Self {
            opaque: false,
            glow: 0,
        }
    }
}

const fn default_as_true() -> bool {
    true
}

const fn default_as_below() -> DrawLayer {
    DrawLayer::Below
}

#[derive(Hash, PartialEq, Eq, Clone, Debug, Default)]
pub enum ScriptKey {
    #[default]
    None,
    World(String),
    Builtin(&'static str),
}

impl ScriptKey {
    pub fn name(&self) -> &str {
        match self {
            ScriptKey::None => "<none>",
            ScriptKey::World(name) => name.as_str(),
            ScriptKey::Builtin(name) => *name
        }
    }

    /// Attempt to find and return the source for the given script key:
    /// - For `None`, return Ok(None) since there's not a script to find
    /// - For `World`, return either Ok(Some(&str)) or Err if it's not in the given hashmap
    /// - For `Builtin`, return Ok(Some(&str)) assuming the builtin is a valid name (Err in the unlikely case...)
    pub fn source<'a>(&self, sources: &'a HashMap<String, String>) -> Result<Option<&'a str>, String> {
        match self {
            ScriptKey::None => Ok(None),
            ScriptKey::World(name) => sources.get(name).map(String::as_str)
                .map_or(Err(format!("unknown script '{name}'")), |s| Ok(Some(s))),
            key @ ScriptKey::Builtin(name) => BUILTIN_SOURCES.get(key)
                .map_or(Err(format!("No builtin script '{name}'")), |s| Ok(Some(*s))),
        }
    }
}

impl From<Option<String>> for ScriptKey {
    fn from(s: Option<String>) -> Self {
        s.map_or(Self::None, |s| Self::World(s))
    }
}

/// Everything an object-or-sensor needs to have a Rhai script attached.
/// TODO clean this up some, especially the script_name-vs-builtin_script dichotomy
#[derive(Clone, Default)]
pub struct ScriptAttributes {
    /// Stable identity assigned by [`crate::board::Board::add_object`].
    /// `0` is the sentinel meaning "not yet inserted into a board".
    /// Real ids start at 1 and never change after assignment.
    /// Not serialized — the id is stamped on insert, not stored in map files.
    pub id: ObjectId,
    /// Visual representation of this object. Owned by the object (not derived
    /// from the grid cell), so scripts can change tile, fg, and bg at runtime.
    pub glyph: Glyph,
    /// How this object affects FOV and lighting
    pub optics: Optics,
    /// Compile-key of the Rhai script that drives this object: a name in
    /// [`World::scripts`](crate::world::World::scripts) for a hand-authored object,
    /// or a synthetic `BUILTIN_*` name set when a script-backed archetype is
    /// expanded (see [`builtin_script`](ObjectDef::builtin_script)). `None` means
    /// this object has no script yet.
    pub script_name: ScriptKey,
    /// Embedded built-in script source, set when a script-backed archetype (e.g. a
    /// `pusher_*` or `gem`) is expanded into an object at load time (see
    /// [`crate::builtin_scripts`]). When set, this is the object's script *source*
    /// (its compile-key is the synthetic `BUILTIN_*` [`script_name`](ObjectDef::script_name)
    /// the same expansion assigns). Not part of the map file — it is regenerated
    /// from the archetype on load.
    /// Open-ended string labels for this object. Serialized as a TOML array;
    /// not subject to any rate limit — mutations take effect immediately after
    /// the frame's action queue is drained.
    pub tags: HashSet<String>,
    /// Optional unique human-readable name for this object. `None` if unnamed.
    /// Names are validated for uniqueness at map-load time; a duplicate name is
    /// cleared to `None` (the object survives but becomes anonymous).
    pub name: Option<String>,
    /// The output queue of actions for this object
    pub queue: ObjQueue,
}

/// A `Sensor` is some kind of object that exists alongside the map: it's drawn on the board but can't
/// affect board movement, as it doesn't live in the grid.
#[derive(Clone)]
pub struct Sensor {
    /// Where it is on the board: x coord
    pub x: usize,
    /// Where it is on the board: y coord
    pub y: usize,
    /// Whether this is drawn above or below the grid
    pub draw_layer: DrawLayer,
    /// Sensors have scripting ability
    pub scripting: ScriptAttributes,
}

/// The serialized representation of a Sensor. Can be turned into a Sensor, or vice versa
#[derive(Serialize, Deserialize, Clone)]
pub struct SensorSpec {
    pub x: usize,
    pub y: usize,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub script: Option<String>,
    #[serde(default, skip_serializing_if = "Glyph::is_transparent")]
    pub glyph: Glyph,
    #[serde(flatten, default)]
    pub optics: Optics,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub name: Option<String>,
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub tags: Vec<String>,
    #[serde(default = "default_as_below")]
    pub draw_layer: DrawLayer,
}

impl SensorSpec {
    pub fn into_sensor(self, next_object_id: &mut ObjectId) -> Sensor {
        let id = *next_object_id;
        *next_object_id += 1;
        Sensor {
            x: self.x,
            y: self.y,
            draw_layer: self.draw_layer,
            scripting: ScriptAttributes {
                id,
                glyph: self.glyph,
                optics: self.optics,
                name: self.name,
                tags: self.tags.into_iter().collect(),
                script_name: self.script.into(),
                ..Default::default()
            }
        }
    }
}

pub trait Hookable {
    fn scriptable(&self) -> &ScriptAttributes;
    fn location(&self) -> (usize, usize);
    fn id(&self) -> ObjectId {
        self.scriptable().id
    }
    fn glyph(&self) -> Glyph {
        self.scriptable().glyph
    }
    fn optics(&self) -> Optics {
        self.scriptable().optics
    }
    fn name(&self) -> &Option<String> {
        &self.scriptable().name
    }
    fn tags(&self) -> &HashSet<String> {
        &self.scriptable().tags
    }
    fn solid(&self) -> bool;
    /// The compile-key for an object's script: the object's `script_name` — a
    /// world-pool name for a named script, or a synthetic `BUILTIN_*` name set by
    /// [`Board::expand_builtin_archetypes`](crate::board::Board::expand_builtin_archetypes)
    /// for an expanded built-in (so identical built-ins share one compiled AST,
    /// while the source still comes from `builtin_script`). `None` if the object has
    /// no script.
    fn script_key(&self) -> &ScriptKey {
        &self.scriptable().script_name
    }
}

impl Hookable for &Sensor {
    fn scriptable(&self) -> &ScriptAttributes {
        &self.scripting
    }
    fn location(&self) -> (usize, usize) {
        (self.x, self.y)
    }
    fn solid(&self) -> bool {
        false
    }
}

pub struct LocatedObject<'a>(pub &'a ObjectDef, pub (usize, usize));

impl Hookable for LocatedObject<'_> {
    fn scriptable(&self) -> &ScriptAttributes {
        &self.0.scripting
    }
    fn location(&self) -> (usize, usize) {
        self.1
    }
    fn solid(&self) -> bool {
        true
    }
}

#[derive(Clone, Debug)]
pub enum Tile {
    Player,
    Object(Box<ObjectDef>),
}

impl Tile {
    pub fn glyph(&self) -> Glyph {
        match self {
            Tile::Player => Glyph::player(),
            Tile::Object(obj) => obj.scripting.glyph,
        }
    }

    pub fn player(&self) -> bool {
        matches!(self, Self::Player)
    }

    /// Can this tile be moved by a `shift`?
    pub fn shiftable(&self) -> bool {
        match self {
            Tile::Player => true, // Player will shift anywhere
            Tile::Object(obj) => {
                match obj.enter_response {
                    EnterResponse::Push(p) => p != No,
                    EnterResponse::Hook | EnterResponse::Block => false, // Blockers never shift
                    EnterResponse::Grab | EnterResponse::Swap | EnterResponse::Squish => true,
                }
            }
        }
    }
}

/// The serialized representation of a Tile. Can be turned into a Tile, or vice versa
#[derive(Serialize, Deserialize, Clone, Debug)]
#[serde(rename_all = "lowercase", tag = "type")]
pub enum TileSpec {
    Player,
    Object {
        #[serde(default, skip_serializing_if = "Option::is_none")]
        script: Option<String>,
        enter: EnterResponse,
        #[serde(flatten)]
        glyph: Glyph,
        #[serde(flatten, default)]
        optics: Optics,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        name: Option<String>,
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        tags: Vec<String>,
    },
    Builtin {
        kind: String,
        #[serde(flatten, default, skip_serializing_if = "Option::is_none")]
        glyph: Option<Glyph>,
    }
}

pub trait IntoTile {
    fn into_tile(self, next_object_id: &mut ObjectId) -> Result<Tile, String>;
}

impl IntoTile for TileSpec {
    fn into_tile(self, next_object_id: &mut ObjectId) -> Result<Tile, String> {
        match self {
            TileSpec::Player => Ok(Tile::Player),
            // TileSpec::Portal { name, target_board, target_name } => {
            //     let def = PortalDef {
            //         name,
            //         target_map: target_board,
            //         target_entry: target_name,
            //     };
            //     Ok(Tile::Portal(Box::new(def)))
            // }
            TileSpec::Object { script, enter, glyph, optics, name, tags } => {
                let def = ObjectDef {
                    enter_response: enter,
                    scripting: ScriptAttributes {
                        id: *next_object_id,
                        glyph,
                        optics,
                        script_name: script.into(),
                        tags: tags.into_iter().collect(),
                        name,
                        queue: ObjQueue::new(),
                    }
                };
                *next_object_id = *next_object_id + 1;

                Ok(Tile::Object(Box::new(def)))
            },
            TileSpec::Builtin { kind, glyph } => {
                if let Some((builtin, variant)) = Builtin::from_name(&kind) {
                    let def = ObjectDef {
                        enter_response: builtin.enter_response(),
                        scripting: ScriptAttributes {
                            id: *next_object_id,
                            glyph: glyph.unwrap_or(builtin.default_glyph_for(variant)),
                            optics: builtin.optics(),
                            script_name: builtin.script(),
                            tags: HashSet::from([format!("BUILTIN_{}", variant)]),
                            name: None,
                            queue: ObjQueue::new(),
                        }
                    };
                    *next_object_id = *next_object_id + 1;
                    Ok(Tile::Object(Box::new(def)))
                } else {
                    Err(format!("Unknown builtin kind {}", kind))
                }
            }
        }
    }
}

/// Convenience functions for tests
#[cfg(test)]
impl TileSpec {
    pub fn wall() -> Self {
        TileSpec::Builtin { kind: "wall".to_string(), glyph: None }
    }
    pub fn player() -> Self {
        TileSpec::Player
    }
    pub fn krate() -> Self {
        TileSpec::Builtin { kind: "crate".to_string(), glyph: None }
    }
    pub fn gem() -> Self {
        TileSpec::Builtin { kind: "gem".to_string(), glyph: None }
    }
}

#[derive(Serialize, Deserialize, Copy, Clone)]
#[serde(rename_all = "lowercase")]
pub enum FloorSpec {
    Biome(FloorBiome),
    Glyph(Glyph),
}

pub trait IntoFloor {
    fn into_floor(self, width: usize, height: usize) -> Floor;
}

impl IntoFloor for Option<FloorSpec> {
    fn into_floor(self, width: usize, height: usize) -> Floor {
        match self {
            Some(FloorSpec::Biome(biome)) => Floor::biome(biome, width, height),
            Some(FloorSpec::Glyph(glyph)) => Floor::Fixed(glyph),
            None => Floor::Blank
        }
    }
}