use std::{collections::HashMap, convert::From, rc::Rc};

use crate::{
    builtin::Builtin,
    symbol_table::{DefId, SymbolTable},
    type_inference::TypeId,
};

//TODO most of these Clone impls only exist to support function application, because the
//tree-walking evaluator moves the reduced IR members.

/// The reduced intermediate representation consists of a list of function definitions, and a block
/// of entrypoint statements.  In a repl or script context this can be an arbitrary list of
/// statements, in an executable context will likely just be a pointer to the main() function.
#[derive(Debug)]
pub struct ReducedIR {
    pub functions: HashMap<DefId, FunctionDefinition>,
    pub entrypoint: Vec<Statement>,
}

impl ReducedIR {
    #[allow(dead_code)]
    pub fn debug(&self, symbol_table: &SymbolTable) {
        println!("Reduced IR:");
        println!("Functions:");
        println!("-----------");
        for (id, callable) in self.functions.iter() {
            let name = &symbol_table.lookup_symbol_by_def(id).unwrap().local_name();
            println!("{}({}) -> {:?}", id, name, callable);
        }
        println!();
        println!("Entrypoint:");
        println!("-----------");
        for stmt in self.entrypoint.iter() {
            println!("{:?}", stmt);
        }
        println!("-----------");
    }
}

#[derive(Debug, Clone)]
pub enum Statement {
    Expression(Expression),
    Binding { id: DefId, constant: bool, expr: Expression },
    Return(Expression),
    Continue,
    Break,
}

#[derive(Debug, Clone)]
pub enum Expression {
    Literal(Literal),
    Tuple(Vec<Expression>),
    List(Vec<Expression>),
    Lookup(Lookup),
    Assign { lval: DefId, rval: Box<Expression> },
    Access { name: String, expr: Box<Expression> },
    Callable(Callable),
    Call { f: Box<Expression>, args: Vec<Expression> },
    Conditional { cond: Box<Expression>, then_clause: Vec<Statement>, else_clause: Vec<Statement> },
    CaseMatch { cond: Box<Expression>, alternatives: Vec<Alternative> },
    Loop { cond: Box<Expression>, statements: Vec<Statement> },
    Index { indexee: Box<Expression>, indexer: Box<Expression> },
    ReductionError(String),
}

impl Expression {
    pub fn unit() -> Self {
        Expression::Tuple(vec![])
    }
}

#[derive(Debug)]
pub struct FunctionDefinition {
    pub body: Vec<Statement>,
}

#[derive(Debug, Clone)]
pub enum Callable {
    Builtin(Builtin),
    UserDefined(DefId),
    Lambda { arity: u8, body: Vec<Statement> },
    DataConstructor { type_id: TypeId, tag: u32 },
    RecordConstructor { type_id: TypeId, tag: u32, field_order: Vec<String> },
}

#[derive(Debug, Clone)]
pub enum Lookup {
    LocalVar(DefId),
    GlobalVar(DefId),
    Function(DefId),
    Param(u8),
}

#[derive(Debug, Clone, PartialEq)]
pub enum Literal {
    Nat(u64),
    Int(i64),
    Float(f64),
    Bool(bool),
    StringLit(Rc<String>),
}

#[derive(Debug, Clone)]
pub struct Alternative {
    pub pattern: Pattern,
    pub item: Vec<Statement>,
}

#[derive(Debug, Clone)]
pub enum Pattern {
    Tuple { subpatterns: Vec<Pattern>, tag: Option<u32> },
    Record { tag: u32, subpatterns: Vec<(Rc<String>, Pattern)> },
    Literal(Literal),
    Ignored,
    Binding(DefId),
}

#[allow(dead_code)]
#[derive(Debug)]
pub struct PatternError {
    msg: String,
}

impl From<&str> for PatternError {
    fn from(s: &str) -> Self {
        Self { msg: s.to_string() }
    }
}

impl From<String> for PatternError {
    fn from(msg: String) -> Self {
        Self { msg }
    }
}