//! Types used in the interpreter.

use crate::ast;
use std::backtrace::Backtrace;
use std::collections::BTreeMap;
use std::collections::HashMap;

#[derive(Debug)]
pub enum Error {
    DuplicateEnvNames(ast::EnvName, Backtrace),
    DuplicateNames(ast::Name, Backtrace),
    NameNotFound(ast::Name, Backtrace),
    FieldNotFound(ast::Label, Backtrace),
    EnvNotFound(ast::EnvName, Backtrace),
    LastStatementNotAnExpr(Backtrace),
    NotAFunction(ast::Expr, Backtrace),
    NotARecord(ast::Value, Backtrace),
    NotAReference(ast::Value, Backtrace),
    NotABoolean(ast::Value, Backtrace),
    ArgumentsMismatch(Backtrace),
}
impl PartialEq for Error {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Error::DuplicateEnvNames(a1, _), Error::DuplicateEnvNames(a2, _)) => a1 == a2,
            (Error::DuplicateNames(a1, _), Error::DuplicateNames(a2, _)) => a1 == a2,
            (Error::NameNotFound(a1, _), Error::NameNotFound(a2, _)) => a1 == a2,
            (Error::FieldNotFound(a1, _), Error::FieldNotFound(a2, _)) => a1 == a2,
            (Error::EnvNotFound(a1, _), Error::EnvNotFound(a2, _)) => a1 == a2,
            (Error::LastStatementNotAnExpr(_), Error::LastStatementNotAnExpr(_)) => true,

            (Error::NotAFunction(a1, _), Error::NotAFunction(a2, _)) => a1 == a2,
            (Error::NotARecord(a1, _), Error::NotARecord(a2, _)) => a1 == a2,
            (Error::NotAReference(a1, _), Error::NotAReference(a2, _)) => a1 == a2,
            (Error::NotABoolean(a1, _), Error::NotABoolean(a2, _)) => a1 == a2,
            (Error::ArgumentsMismatch(_), Error::ArgumentsMismatch(_)) => true,
            _ => false,
        }
    }
}

impl std::fmt::Display for Error {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Error::DuplicateEnvNames(a, b) => {
                write!(
                    f,
                    "Closure generation failed. Duplicate env names: {a:?}\n{b}"
                )
            }
            Error::DuplicateNames(a, b) => write!(f, "Duplicate names: {a:?}\n{b}"),
            Error::NameNotFound(a, b) => write!(f, "Name not found: {a:?}\n{b}"),
            Error::FieldNotFound(a, b) => write!(f, "Field not found: {a:?}\n{b}"),
            Error::EnvNotFound(a, b) => write!(f, "Env not found: {a:?}\n{b}"),
            Error::LastStatementNotAnExpr(a) => {
                write!(f, "Last statement is not an expression\n{a}")
            }
            Error::NotAFunction(a, b) => write!(f, "Not a function {a:?}\n{b}"),
            Error::NotARecord(a, b) => write!(f, "Not a record {a:?}\n{b}"),
            Error::NotAReference(a, b) => write!(f, "Not a reference {a:?}\n{b}"),
            Error::NotABoolean(a, b) => write!(f, "Not a boolean {a:?}\n{b}"),
            Error::ArgumentsMismatch(a) => write!(f, "Arguments mismatch\n{a}"),
        }
    }
}

impl From<ast::Error> for Error {
    fn from(error: ast::Error) -> Error {
        match error {
            ast::Error::LabelNotFound(l) => Error::FieldNotFound(l, Backtrace::capture()),
        }
    }
}

#[derive(PartialEq, Debug, Clone)]
struct Namer {
    counter: u64,
}
impl Namer {
    fn new() -> Namer {
        Namer { counter: 0 }
    }
    pub fn next(&mut self) -> u64 {
        self.counter += 1;
        self.counter
    }
}

pub struct State {
    pub name: String,
    env_namer: Namer,
    pub envs: Envs,
    pub variables: Variables,
    pub primitive_funcs: PrimitiveFuncs,
}

pub struct PrimitiveFuncs {
    pub map: HashMap<ast::Name, PrimFunc>,
}

pub type PrimFunc = fn(Vec<ast::Value>) -> ast::Value;

impl PrimitiveFuncs {
    pub fn new(prims: Vec<(&str, PrimFunc)>) -> Self {
        let mut map: HashMap<ast::Name, PrimFunc> = HashMap::new();
        for (key, func) in prims.into_iter() {
            map.insert(key.into(), func);
        }
        PrimitiveFuncs { map }
    }
    pub fn get(&self, name: &ast::Name) -> Option<&PrimFunc> {
        self.map.get(name)
    }
}

pub struct Variables {
    pub vars: HashMap<ast::Ref, ast::Value>,
    namer: Namer,
}

impl Variables {
    pub fn new() -> Self {
        Variables {
            vars: HashMap::new(),
            namer: Namer::new(),
        }
    }
    pub fn insert(&mut self, value: ast::Value) -> ast::Ref {
        let name = ast::Ref(self.namer.next());
        self.vars.insert(name.clone(), value);
        name
    }
    pub fn get<'a>(&'a self, reference: &ast::Ref) -> &'a ast::Value {
        self.vars.get(reference).unwrap()
    }
    pub fn set(&mut self, reference: ast::Ref, new_value: ast::Value) {
        self.vars.insert(reference, new_value);
    }
}
impl State {
    pub fn new(name: String, primitive_funcs: PrimitiveFuncs) -> State {
        State {
            name,
            env_namer: Namer::new(),
            envs: Envs(BTreeMap::new()),
            variables: Variables::new(),
            primitive_funcs,
        }
    }
    pub fn generate_env(&mut self, env: Env) -> Result<ast::EnvName, Error> {
        let env_name = ast::EnvName(format!("{}_{}", self.name, self.env_namer.next()));
        self.envs.insert(&env_name, env)?;
        Ok(env_name)
    }
}

#[derive(PartialEq, Debug, Clone)]
pub struct Env {
    env: BTreeMap<ast::Name, ast::Value>,
    pub name: ast::EnvName,
}

impl Env {
    pub fn new(name: ast::EnvName) -> Env {
        Env {
            env: BTreeMap::new(),
            name,
        }
    }
    pub fn get(&self, name: &ast::Name) -> Result<&ast::Value, Error> {
        self.env
            .get(name)
            .ok_or(Error::NameNotFound(name.clone(), Backtrace::capture()))
    }
    pub fn insert(&mut self, name: ast::Name, value: ast::Value) {
        self.env.insert(name.clone(), value);
    }
    pub fn insert_nodup(&mut self, name: &ast::Name, value: ast::Value) -> Result<(), Error> {
        if self.env.insert(name.clone(), value).is_some() {
            Err(Error::DuplicateNames(name.clone(), Backtrace::capture()))
        } else {
            Ok(())
        }
    }
}

#[derive(PartialEq, Debug, Clone)]
pub struct Envs(pub BTreeMap<ast::EnvName, Env>);

impl Envs {
    pub fn get(&self, env_name: &ast::EnvName) -> Result<&Env, Error> {
        self.0
            .get(env_name)
            .ok_or(Error::EnvNotFound(env_name.clone(), Backtrace::capture()))
    }
    pub fn get_mut(&mut self, env_name: &ast::EnvName) -> Result<&mut Env, Error> {
        self.0
            .get_mut(env_name)
            .ok_or(Error::EnvNotFound(env_name.clone(), Backtrace::capture()))
    }
    pub fn insert(&mut self, name: &ast::EnvName, env: Env) -> Result<(), Error> {
        if self.0.insert(name.clone(), env).is_some() {
            Err(Error::DuplicateEnvNames(name.clone(), Backtrace::capture()))
        } else {
            Ok(())
        }
    }
}