use bevy::prelude::*;
use bevy::math::DVec3;
use bevy_xpbd_3d::prelude::*;
use serde_yaml::Value;
use serde::Deserialize;
use crate::{actor, audio, hud, settings, world, effects};

pub const CHATS: &[&str] = &[
    include_str!("chats/serenity.yaml"),
    include_str!("chats/startrans.yaml"),
];

pub const TOKEN_CHAT: &str = "chat";
pub const TOKEN_MSG: &str = "msg";
pub const TOKEN_SYSTEM: &str = "system";
pub const TOKEN_WARN: &str = "warn";
pub const TOKEN_SLEEP: &str = "sleep";
pub const TOKEN_SET: &str = "set";
pub const TOKEN_IF: &str = "if";
pub const TOKEN_GOTO: &str = "goto";
pub const TOKEN_LABEL: &str = "label";
pub const TOKEN_SCRIPT: &str = "script";
pub const TOKEN_SOUND: &str = "sound";
pub const TOKEN_GOTO_EXIT: &str = "EXIT";

pub const DEFAULT_SOUND: &str = "chat";
pub const MAX_BRANCH_DEPTH: usize = 64;

pub const CHOICE_TIMER: f64 = 40.0 * settings::DEFAULT_CHAT_SPEED as f64;
pub const LETTERS_PER_SECOND: f32 = 17.0;
pub const TALKER_SPEED_FACTOR: f32 = settings::DEFAULT_CHAT_SPEED / LETTERS_PER_SECOND;
pub const CHAT_SPEED_MIN_LEN: f32 = 40.0;

pub const NON_CHOICE_TOKENS: &[&str] = &[
    TOKEN_CHAT,
    TOKEN_MSG,
    TOKEN_SYSTEM,
    TOKEN_WARN,
    TOKEN_SLEEP,
    TOKEN_SET,
    TOKEN_IF,
    TOKEN_GOTO,
    TOKEN_LABEL,
    TOKEN_SCRIPT,
    TOKEN_SOUND,
];

pub struct ChatPlugin;
impl Plugin for ChatPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, load_chats);
        app.add_systems(Update, (
            handle_reply_keys.before(handle_chat_timer),
            handle_chat_timer.before(handle_chat_events),
            handle_new_conversations.before(handle_chat_events),
            handle_chat_events.before(handle_chat_scripts),
            handle_chat_scripts,
        ));
        app.add_event::<StartConversationEvent>();
        app.add_event::<ChatEvent>();
        app.add_event::<ChatScriptEvent>();
        app.insert_resource(ChatDB(Vec::new()));
    }
}

type ChatPos = Vec<usize>;

#[derive(Component)]
pub struct Chat {
    pub id: usize,
    pub position: ChatPos,
    pub timer: f64,
    pub talker: Talker,
}

#[derive(Component)]
pub struct Choice {
    pub text: String,
    pub key: usize,
    pub goto: ChatPos,
}

#[derive(Component)]
#[derive(Clone)]
pub struct Talker {
    pub conv_id: String,
    pub name: Option<String>,
    pub pronoun: Option<String>,
    pub talking_speed: f32,
}

#[derive(Event)]
pub struct StartConversationEvent {
    pub talker: Talker,
}

#[derive(Event)]
pub struct ChatScriptEvent(String);

#[derive(Event)]
pub enum ChatEvent {
    DespawnAllChoices,
    DespawnAllChats,
    SpawnMessage(String, hud::LogLevel, String),
    SpawnChoice(String, usize, ChatPos),
    RunScript(String),
    Sleep(f64),
    //Script(String, String, String),
}

// This is the only place where any YAML interaction should be happening.
#[derive(Resource)]
pub struct ChatDB(Vec<Value>);
impl ChatDB {
    pub fn load_from_str(&mut self, yaml_string: &str) -> Result<(), ()> {
        let mut count = 0;
        for document in serde_yaml::Deserializer::from_str(yaml_string) {
            match Value::deserialize(document) {
                Ok(yaml_data) => {
                    if let Value::Sequence(yaml_sequence) = yaml_data {
                        self.0.push(Value::Sequence(yaml_sequence));
                        count += 1;
                    }
                    else {
                        error!("Could not load YAML: {:?}", yaml_data);
                    }
                }
                Err(error) => {
                    dbg!(error);
                    return Err(());
                }
            }
        }
        info!("Loaded {count} conversations");
        return Ok(());
    }

    pub fn get_chat_by_id(&self, id: &String) -> Result<usize, String> {
        let mut found: Option<usize> = None;
        for (index, object_yaml) in self.0.iter().enumerate() {
            if let Some(chat_id) = object_yaml[0][TOKEN_CHAT].as_str() {
                if chat_id == id {
                    if found.is_some() {
                        return Err("Found multiple chats with the same id!".to_string());
                    }
                    found = Some(index);
                }
            }
        }
        if let Some(result) = found {
            return Ok(result);
        }
        return Err(format!("No chat with the conversation ID `{id}` was found."));
    }

    // For a given Value, check whether it's a Value::Mapping and whether it
    // contains a choice.  Mappings that will be detected as choices:
    // - `{"What's up?": [...]}`
    // - `{"What's up?": [...], "if": "value > 3"}`
    // Not acceptable:
    // - `"What's up?"`
    // - `{"goto": "foo"}`
    fn search_choice(&self, yaml: Option<&Value>) -> Option<(String, Value)> {
        let non_choice_tokens = NON_CHOICE_TOKENS.to_vec();
        if let Some(Value::Mapping(map)) = yaml {
            for key in map.keys() {
                if let Value::String(key) = key {
                    if non_choice_tokens.contains(&key.as_str()) {
                        continue;
                    }
                    return Some((key.into(), map[key].clone()));
                }
            }
        }
        return None;
    }

    fn search_label_recursively(&self, sequence: &Value, label: &String, mut pos: ChatPos) -> Option<ChatPos> {
        if pos.len() > MAX_BRANCH_DEPTH {
            return None;
        }
        if let Some(vector) = sequence.as_sequence() {
            for (index, item) in vector.iter().enumerate() {
                match item {
                    Value::String(_) => {}
                    Value::Mapping(map) => {
                        for (key, value) in map {
                            if let Some(key) = key.as_str() {
                                if key == TOKEN_LABEL {
                                    if value == label {
                                        pos.push(index);
                                        return Some(pos);
                                    }
                                }
                            }
                            if value.is_sequence() {
                                pos.push(index);
                                if let Some(result) = self.search_label_recursively(
                                        value, label, pos.clone()) {
                                    return Some(result)
                                }
                                pos.pop();
                            }
                        }
                    }
                    _ => {}
                }
            }
        }
        return None;
    }

    fn search_label(&self, chat_id: usize, label: &String) -> Option<ChatPos> {
        if label == TOKEN_GOTO_EXIT {
            return Some(vec![]);
        }
        return self.search_label_recursively(&self.0[chat_id], label, vec![]);
    }

    // returns true if we reached the end of a branch and possibly popped the position stack
    fn advance_pointer(&self, chat: &mut Chat) -> bool {
        let len = chat.position.len();
        if len == 0 {
            return true; // out of bounds
        }
        chat.position[len - 1] += 1;

        let mut popped = false;
        while chat.position.len() > 0 {
            match self.at(chat.id, &chat.position) {
                None => {
                    chat.position.pop();
                    popped = true;
                    if chat.position.len() > 0 {
                        let index = chat.position.len() - 1;
                        chat.position[index] += 1;
                    }
                },
                Some(_) => {
                    break;
                }
            }
        }
        if chat.position.len() == 0 {
            return true; // out of bounds
        }
        return popped;
    }

    // Returns the Value at the given ID/position, as-is.
    // If it's a choice, it returns the entire {"choice text": [...]} mapping.
    fn at(&self, id: usize, position: &Vec<usize>) -> Option<Value> {
        if position.len() == 0 {
            return None;
        }
        let mut result: Option<Value> = None;
        let mut pointer: Option<Value> = Some(self.0[id].clone());
        let mut next_pointer: Option<Value> = None;
        for index in position {
            if let Some(Value::Sequence(seq)) = &pointer {
                let value = seq.get(*index);
                match value {
                    Some(Value::String(value_string)) => {
                        result = Some(Value::String(value_string.into()));
                    }
                    Some(Value::Mapping(mapping)) => {
                        if let Some((_choicetext, subconversation)) = self.search_choice(value) {
                            result = Some(Value::Mapping(mapping.clone()));
                            next_pointer = Some(subconversation);
                        }
                        else {
                            result = Some(Value::Mapping(mapping.clone()));
                        }
                    }
                    None => {
                        return None; // Out of bounds.
                    }
                    _ => {
                        error!("Could not handle YAML value {value:?}");
                        return None;
                    }
                }
                pointer = next_pointer;
                next_pointer = None;
            } else {
                return None;
            }
        }
        return result;
    }

    pub fn process_yaml_entry(
        &self,
        chat: &mut Chat,
        event: &mut EventWriter<ChatEvent>,
    ) -> bool {
        let current_item = self.at(chat.id, &chat.position);
        let mut add_choices = true;
        match current_item {
            Some(Value::String(message)) => {
                event.send(ChatEvent::SpawnMessage(message.to_string(),
                    hud::LogLevel::Chat, DEFAULT_SOUND.to_string()));
            }
            Some(Value::Mapping(map)) => {
                if let Some(_) = self.search_choice(Some(&Value::Mapping(map.clone()))) {
                    add_choices = false;
                }
                let mut sound = "chat".to_string();

                // We're going through the list of keys/values multiple times
                // to ensure that dependencies for certain commands are available

                // First pass
                for (key, value) in &map {
                    let key = key.as_str();
                    match (key, value) {
                        (Some(TOKEN_SET), _) => {}
                        (Some(TOKEN_IF), _) => {}
                        (Some(TOKEN_SOUND), Value::String(sound_name)) => {
                            sound = sound_name.clone();
                        }
                        _ => {}
                    }
                }

                // Second pass
                for (key, value) in &map {
                    let key = key.as_str();
                    match (key, value) {
                        (Some(TOKEN_MSG), Value::String(message)) => {
                            event.send(ChatEvent::SpawnMessage(
                                    message.to_string(), hud::LogLevel::Chat, sound.clone()));
                        }
                        (Some(TOKEN_SYSTEM), Value::String(message)) => {
                            event.send(ChatEvent::SpawnMessage(
                                    message.to_string(), hud::LogLevel::Info, sound.clone()));
                        }
                        (Some(TOKEN_WARN), Value::String(message)) => {
                            event.send(ChatEvent::SpawnMessage(
                                    message.to_string(), hud::LogLevel::Warning, sound.clone()));
                        }
                        _ => {}
                    }
                }

                // Third pass
                for (key, value) in &map {
                    let key = key.as_str();
                    match (key, value) {
                        (Some(TOKEN_SLEEP), Value::Number(time)) => {
                            if let Some(time_f64) = time.as_f64() {
                                event.send(ChatEvent::Sleep(time_f64));
                            }
                        }
                        (Some(TOKEN_GOTO), Value::String(label)) => {
                            match self.search_label(chat.id, &label) {
                                Some(pos) => {
                                    chat.position = pos;
                                }
                                None => {
                                    error!("Could not find goto label {label}!");
                                }
                            }
                        }
                        (Some(TOKEN_SCRIPT), Value::String(script)) => {
                            event.send(ChatEvent::RunScript(script.clone()));
                        }
                        _ => {}
                    }
                }
            }
            None => {
                if chat.position.len() == 0 {
                    event.send(ChatEvent::SpawnMessage("Disconnected.".to_string(),
                        hud::LogLevel::Info, DEFAULT_SOUND.to_string()));
                    event.send(ChatEvent::DespawnAllChats);
                }
            }
            _ => {
                error!("Can't handle YAML value {current_item:?}");
            }
        }
        return add_choices;
    }

    pub fn advance_chat(&self, chat: &mut Chat, event: &mut EventWriter<ChatEvent>) {
        event.send(ChatEvent::DespawnAllChoices);

        // Handle this entry in the chat list
        let add_choices = self.process_yaml_entry(chat, event);

        // Move on to next entry
        let mut finished_branch = self.advance_pointer(chat);

        // Add choices, if available
        if add_choices {
            let mut key: usize = 0;
            while let Some((choice, _)) =
                    self.search_choice(self.at(chat.id, &chat.position).as_ref()) {
                if finished_branch {
                    break;
                }
                let mut goto: Vec<usize> = chat.position.clone();
                goto.push(0);
                event.send(ChatEvent::SpawnChoice(choice, key, goto));
                key += 1;
                finished_branch = self.advance_pointer(chat);
            }
        }
    }
}

pub fn load_chats(mut chatdb: ResMut<ChatDB>) {
    for chat_yaml in CHATS {
        if chatdb.load_from_str(chat_yaml).is_err() {
            error!("Could not load chat definitions.  Validate files in `src/chats/` path.");
        }
    }
}

pub fn handle_new_conversations(
    mut commands: Commands,
    mut er_conv: EventReader<StartConversationEvent>,
    mut ew_sfx: EventWriter<audio::PlaySfxEvent>,
    mut ew_chatevent: EventWriter<ChatEvent>,
    chatdb: Res<ChatDB>,
    q_chats: Query<&Chat>,
    time: Res<Time>,
) {
    for event in er_conv.read() {
        if !q_chats.is_empty() {
            ew_sfx.send(audio::PlaySfxEvent(audio::Sfx::Ping));
            return;
        }
        match (*chatdb).get_chat_by_id(&event.talker.conv_id) {
            Ok(chat_id) => {
                let mut chat = Chat {
                    id: chat_id,
                    position: vec![0],
                    timer: time.elapsed_seconds_f64(),
                    talker: event.talker.clone(),
                };
                chatdb.advance_chat(&mut chat, &mut ew_chatevent);
                commands.spawn((
                    chat,
                    world::DespawnOnPlayerDeath,
                ));
            }
            Err(error) => {
                error!("Error while looking for chat ID: {error}");
            }
        }
    }
}

pub fn handle_chat_timer(
    time: Res<Time>,
    chatdb: Res<ChatDB>,
    mut q_chats: Query<&mut Chat>,
    mut ew_chatevent: EventWriter<ChatEvent>,
) {
    let now = time.elapsed_seconds_f64();
    for mut chat in &mut q_chats {
        if now >= chat.timer {
            chatdb.advance_chat(&mut chat, &mut ew_chatevent);
        }
    }
}

pub fn handle_chat_events(
    mut commands: Commands,
    mut er_chatevent: EventReader<ChatEvent>,
    mut ew_chatscript: EventWriter<ChatScriptEvent>,
    mut ew_sfx: EventWriter<audio::PlaySfxEvent>,
    mut log: ResMut<hud::Log>,
    q_choices: Query<Entity, With<Choice>>,
    mut q_chats: Query<(Entity, &mut Chat)>,
    time: Res<Time>,
    settings: Res<settings::Settings>,
) {
    for event in er_chatevent.read() {
        let now = time.elapsed_seconds_f64();
        let chat_maybe = q_chats.get_single_mut();
        if chat_maybe.is_err() {
            return;
        }
        let (chat_entity, mut chat) = chat_maybe.unwrap();

        match event {
            ChatEvent::DespawnAllChoices => {
                for entity in &q_choices {
                    commands.entity(entity).despawn();
                }
            }
            ChatEvent::DespawnAllChats => {
                commands.entity(chat_entity).despawn();
            }
            ChatEvent::SpawnMessage(message, level, sound) => {
                match level {
                    hud::LogLevel::Chat => {
                        log.chat(message.into(), chat.talker.name.clone().unwrap_or("".to_string()));
                    }
                    hud::LogLevel::Info | hud::LogLevel::Notice => {
                        log.info(message.into());
                    }
                    hud::LogLevel::Warning => {
                        log.warning(message.into());
                    }
                }
                chat.timer = now + ((message.len() as f32).max(CHAT_SPEED_MIN_LEN) * TALKER_SPEED_FACTOR * chat.talker.talking_speed / settings.chat_speed) as f64;

                let sfx = audio::str2sfx(sound);
                ew_sfx.send(audio::PlaySfxEvent(sfx));
            }
            ChatEvent::SpawnChoice(replytext, key, goto) => {
                commands.spawn((
                    world::DespawnOnPlayerDeath,
                    Choice {
                        text: replytext.into(),
                        key: *key,
                        goto: goto.clone(),
                    }
                ));
                chat.timer = now + CHOICE_TIMER / settings.chat_speed as f64;
            }
            ChatEvent::RunScript(script) => {
                ew_chatscript.send(ChatScriptEvent(script.clone()));
            }
            ChatEvent::Sleep(sleep_duration) => {
                chat.timer = now + sleep_duration;
            }
        }
    }
}

fn handle_reply_keys(
    keyboard_input: Res<ButtonInput<KeyCode>>,
    settings: ResMut<settings::Settings>,
    q_choices: Query<&Choice>,
    mut q_chats: Query<&mut Chat>,
    //mut evwriter_sendmsg: EventWriter<SendMessageEvent>,
    mut evwriter_sfx: EventWriter<audio::PlaySfxEvent>,
    time: Res<Time>,
) {
    let mut selected_choice: usize = 0;
    'outer: for key in settings.get_reply_keys() {
        if keyboard_input.just_pressed(key) {
            for choice in &q_choices {
                if choice.key == selected_choice {
                    if let Ok(mut chat) = q_chats.get_single_mut() {
                        evwriter_sfx.send(audio::PlaySfxEvent(audio::Sfx::Click));
                        chat.timer = time.elapsed_seconds_f64();
                        chat.position = choice.goto.clone();
                    }
                    break 'outer;
                }
            }
        }
        selected_choice += 1;
    }
}

pub fn handle_chat_scripts(
    mut er_chatscript: EventReader<ChatScriptEvent>,
    mut q_actor: Query<(&mut actor::Actor, &mut actor::Suit), Without<actor::Player>>,
    mut q_player: Query<(&mut actor::Actor, &mut actor::Suit, &mut actor::ExperiencesGForce), With<actor::Player>>,
    mut q_playercam: Query<(&mut Position, &mut LinearVelocity), With<actor::PlayerCamera>>,
    mut ew_sfx: EventWriter<audio::PlaySfxEvent>,
    mut ew_effect: EventWriter<effects::SpawnEffectEvent>,
) {
    for script in er_chatscript.read() {
        // Parse the script string
        let mut parts = script.0.split_whitespace();
        let name = parts.next();
        if name.is_none() {
            error!("ChatScriptEvent should not contain a script name and its parameters, got empty String");
            return;
        }
        let name = name.unwrap();
        let param1 = parts.next().unwrap_or("");
        let param2 = parts.next().unwrap_or("");

        // Process the script
        match name {
            "refilloxygen" => if let Ok(mut amount) = param1.to_string().parse::<f32>() {
                for (_, mut suit, _) in q_player.iter_mut() {
                    if param2.is_empty() {
                        suit.oxygen = (suit.oxygen + amount).clamp(0.0, suit.oxygen_max);
                    }
                    else {
                        let mut found_other = false;
                        info!("param2={}", param2);
                        for (other_actor, mut other_suit) in q_actor.iter_mut() {
                            if !other_actor.id.is_empty() {
                                info!("ID={}", other_actor.id);
                            }
                            if other_actor.id == param2 {
                                found_other = true;
                                amount = amount
                                    .clamp(0.0, other_suit.oxygen)
                                    .clamp(0.0, suit.oxygen_max - suit.oxygen);
                                other_suit.oxygen = other_suit.oxygen - amount;
                                suit.oxygen = (suit.oxygen + amount).clamp(0.0, suit.oxygen_max);
                                break;
                            }
                        }
                        if !found_other {
                            error!("Script error: could not find actor with ID `{}`", param2);
                        }
                    }
                }
            } else {
                error!("Invalid parameter for command `{}`: `{}`", name, param1);
            }
            "cryotrip" => {
                if param1.is_empty() {
                    error!("Chat script cryotrip needs a parameter");
                }
                else {
                    if let Ok((mut pos, mut v)) = q_playercam.get_single_mut() {
                        if param1 == "oscillation".to_string() {
                            *pos = Position(DVec3::new(147e6, 165e6, 336e6));
                            v.0 = DVec3::ZERO;
                        }
                        else if param1 == "metisprime".to_string() {
                            *pos = Position(DVec3::new(27643e3, -47e3, -124434e3));
                            v.0 = DVec3::ZERO;
                        }
                        else if param1 == "serenity".to_string() {
                            *pos = Position(DVec3::new(-121095e3, 582e3, -190816e3));
                            v.0 = DVec3::ZERO;
                        }
                        else {
                            error!("Invalid destination for cryotrip chat script: '{}'", param1);
                        }
                    }
                    if let Ok((_, mut suit, mut gforce)) = q_player.get_single_mut() {
                        suit.oxygen = suit.oxygen_max;
                        gforce.ignore_gforce_seconds = 1.0;
                    }
                    ew_sfx.send(audio::PlaySfxEvent(audio::Sfx::WakeUp));
                    ew_effect.send(effects::SpawnEffectEvent {
                        class: effects::Effects::FadeIn(Color::CYAN),
                        duration: 1.0,
                    });
                }
            }
            "cryofadeout" => {
                ew_effect.send(effects::SpawnEffectEvent {
                    class: effects::Effects::FadeOut(Color::CYAN),
                    duration: 5.1,
                });
            }
            _ => {
                error!("Error, undefined chat script {name}");
            }
        }
    }
}