use crate::config::directions::Directions;
use crate::config::{Item, State, Subject, Verb};
use regex::Regex;
use serde::{Deserialize, Serialize};

/// Describes the type of action that is
/// being parsed.
/// They are determined based on the
/// combination of input tokens. If
/// an action contains only a verb,
/// such as "look", then it is a
/// `ActionType::Verb` and so on.
/// Invalid actions are returned
/// when the action parser can't
/// determine the type of action.
#[derive(Debug, PartialEq)]
pub enum ActionType {
    /// Action is a single verb
    /// Example: "look", "quit"
    Verb,
    /// Action has a verb and a subject
    /// Example: "talk to subject"
    VerbSubject,
    /// Action has a verb and an item
    /// Example: "take item", "drop item"
    VerbItem,
    /// Action has a verb, an item, and a subject
    /// Example: "give item to subject"
    VerbItemSubject,
    /// An action that failed to be parsed from
    /// the input tokens.
    Invalid,
    /// Action has a direction
    /// Example: "north", "south", "east", "west"
    Movement,
}

/// Actions are the core of the parser.
/// They are used to determine what the
/// player is trying to do.
///
/// The struct `Action` implements its own
/// parser and return a valid action struct
/// with the appropriate data.
///
/// # Examples:
///
/// * "look subject1"
/// ```rust
/// # use nightrunner_lib::parser::action::Action;
/// # use nightrunner_lib::config::{Verb, Subject, VerbFunction};
/// let action_look = Action {
///     verb: Some(Verb {
///         id: 1,
///         names: vec!["look".to_string()],
///         verb_function: VerbFunction::Look
///     }),
///     subject: Some(Subject {
///         id: 1,
///         name: "subject1".to_string(),
///         description: "some verb text".to_string(),
///         default_text: "default text".to_string(),
///     }),
///     item: None,
///     movement: None,
///     command_tokens: vec!["look".to_string(), "subject1".to_string()],
///     input: "look subject1".to_string(),
/// };
/// ```
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub struct Action {
    /// If the action contains a verb,
    /// then this field will be set with the
    /// verb. Currently every action has to
    /// have a verb.
    pub verb: Option<Verb>,
    /// If the action contains a subject,
    /// then this field will be set with the
    /// subject.
    pub subject: Option<Subject>,
    /// If the action contains an item,
    /// then this field will be set with the
    /// item.
    pub item: Option<Item>,
    /// If the action contains a direction,
    /// then this field will be set with the
    /// direction and all other fields will
    /// be set to None.
    pub movement: Option<Directions>,
    /// The tokens from the user input.
    /// This is created by spliting the string
    /// on spaces.
    pub command_tokens: Vec<String>,
    /// The original input from the user.
    pub input: String,
}

impl Action {
    /// Is the action valid?
    pub fn is_valid(&self) -> bool {
        if self.verb.is_some() {
            self.item.is_some()
                || self.subject.is_some()
                || self.movement.is_some()
                || self.verb.is_some()
        } else {
            self.movement.is_some()
        }
    }
    /// Determines the type of action.
    pub fn action_type(&self) -> ActionType {
        if self.is_valid() && self.verb.is_some() && self.item.is_some() && self.subject.is_some() {
            ActionType::VerbItemSubject
        } else if self.is_valid() && self.verb.is_some() && self.subject.is_some() {
            ActionType::VerbSubject
        } else if self.is_valid() && self.verb.is_some() && self.item.is_some() {
            ActionType::VerbItem
        } else if self.is_valid() && self.verb.is_some() {
            ActionType::Verb
        } else if self.is_valid() && self.movement.is_some() {
            ActionType::Movement
        } else {
            ActionType::Invalid
        }
    }
    /// Parses the action.
    ///
    /// It will return an action struct with the
    /// appropriate data.
    /// This function tokenizes the input string
    /// and drops any words contained in the prepositions
    /// or determiners arrays.
    /// If after filtering the input string nothing is left,
    /// it returns an invalid action with all fields set to None.
    pub fn parse(state: &State, input: &str) -> Action {
        let prepositions = state.config.allowed_prepositions.clone().prepositions;
        let determiners = state.config.allowed_determiners.clone().determiners;

        let command_tokens: Vec<String> = input
            .split(' ')
            .collect::<Vec<&str>>()
            .iter()
            .filter(|w| {
                let word: String = w.to_string().to_lowercase();
                !prepositions.contains(&word) && !determiners.contains(&word)
            })
            .map(|word| word.to_string())
            .collect::<Vec<String>>();
        if command_tokens.is_empty() {
            Action {
                item: None,
                movement: None,
                subject: None,
                verb: None,
                command_tokens: vec!["".to_string()],
                input: input.to_string(),
            }
        } else {
            parse_action(state, command_tokens, input)
        }
    }
}

impl std::fmt::Display for Action {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        if !self.is_valid() {
            return write!(f, "Invalid action: {}", self.command_tokens.join(" "));
        }
        match (&self.verb, &self.item, &self.subject, &self.movement) {
            (Some(verb), Some(item), Some(subject), _) => {
                write!(f, "{} {} {}", verb, item, subject.name)
            }
            (Some(verb), None, Some(subject), _) => write!(f, "{} {}", verb, subject.name),
            (Some(verb), Some(item), None, _) => write!(f, "{} {}", verb, item),
            (Some(verb), None, None, _) => write!(f, "{}", verb),
            (None, _, _, Some(movement)) => write!(f, "{}", movement),
            _ => write!(f, "Invalid action: {}", self.command_tokens.join(" ")),
        }
    }
}

impl From<Action> for String {
    fn from(action: Action) -> String {
        action.to_string()
    }
}

impl From<&Action> for String {
    fn from(action: &Action) -> String {
        action.to_string()
    }
}

fn parse_action(state: &State, command_tokens: Vec<String>, input: &str) -> Action {
    let verb = extract_verb(state, &command_tokens);
    let movement = extract_movement(state, &command_tokens);
    let subject = extract_subject(state, &command_tokens);
    let item = extract_item(state, &command_tokens, input);
    Action {
        verb,
        movement,
        item,
        subject,
        command_tokens,
        input: input.to_string(),
    }
}

fn extract_verb(state: &State, command_tokens: &[String]) -> Option<Verb> {
    let verbs = state.config.allowed_verbs.clone();
    verbs
        .iter()
        .find(|v| v.names.contains(&command_tokens[0]))
        .cloned()
}

fn extract_item(state: &State, command_tokens: &[String], input: &str) -> Option<Item> {
    let subjects = state.config.subjects.clone();
    let items_string: String = state
        .config
        .items
        .iter()
        .map(|item| regex::escape(&item.name))
        .collect::<Vec<String>>()
        .join("|");
    let items_regex_match = format!("({})", items_string);
    let re = Regex::new(&items_regex_match)
        .expect("item names are regex-escaped, so the pattern is always valid");

    if command_tokens.len() > 1 && !subjects.iter().any(|s| s.name == command_tokens[1]) {
        re.captures(input)
            .and_then(|capture| capture.get(1))
            .and_then(|matched| {
                state
                    .config
                    .items
                    .iter()
                    .find(|item| item.name == matched.as_str())
                    .cloned()
            })
    } else {
        None
    }
}

fn extract_subject(state: &State, command_tokens: &[String]) -> Option<Subject> {
    let subjects = state.config.subjects.clone();
    match &command_tokens.len() {
        0 | 1 => None,
        2 => subjects
            .iter()
            .find(|s| s.name == command_tokens[1])
            .cloned(),
        _ => subjects
            .iter()
            .find(|s| s.name == command_tokens[&command_tokens.len() - 1])
            .cloned(),
    }
}

// This should be re-worked to use events instead. Maybe v2.0
// Using events allows for commands such "sneak north" to get
// past a sleeping dragon, or a corporate goon standing guard.
// As it stands, the parser is very simple when it comes to mo-
// ving around.
fn extract_movement(state: &State, command_tokens: &[String]) -> Option<Directions> {
    let movements = state.config.allowed_movements.movements.clone();
    let directions = state.config.allowed_directions.directions.clone();
    match command_tokens.len() {
        1 => match &command_tokens[0][..] {
            "north" | "n" => Some(Directions::North),
            "south" | "s" => Some(Directions::South),
            "east" | "e" => Some(Directions::East),
            "west" | "w" => Some(Directions::West),
            _ => None,
        },
        2 => {
            if movements.contains(&command_tokens[0]) && directions.contains(&command_tokens[1]) {
                match &command_tokens[1][..] {
                    "north" | "n" => Some(Directions::North),
                    "south" | "s" => Some(Directions::South),
                    "east" | "e" => Some(Directions::East),
                    "west" | "w" => Some(Directions::West),
                    _ => None,
                }
            } else {
                None
            }
        }
        _ => None,
    }
}

#[cfg(test)]
#[path = "action_tests.rs"]
mod action_tests;
