use crate::ast_compiler::{Expression, Parameter, Statement};
use crate::errors::CompilerError;
use crate::errors::CompilerError::IncompatibleTypes;
use crate::tokens::TokenType::{
    Bool, DateTime, F32, F64, FloatingPoint, Greater, GreaterEqual, I32, I64, Integer, Less,
    LessEqual, ListType, MapType, Minus, ObjectType, Plus, SignedInteger, StringType, U32, U64,
    Unknown, UnsignedInteger,
};
use crate::tokens::{Token, TokenType};
use log::debug;
use std::collections::HashMap;

pub enum Symbol {
    Function {
        name: String,
        parameters: Vec<Parameter>,
        return_type: TokenType,
        body: Vec<Statement>,
    },
    Variable {
        name: String,
        var_type: TokenType,
    },
    Object {
        name: String,
        fields: Vec<Parameter>,
    },
}

fn make_qname(path: &str, name: &Token) -> String {
    if path == "" {
        name.lexeme.to_string()
    } else {
        format!("{}.{}", path, name.lexeme)
    }
}

pub fn build(path: &str, ast: &[Statement], symbols: &mut HashMap<String, Symbol>) {
    for statement in ast {
        match statement {
            Statement::VarStmt { name, var_type, .. } => {
                let key = make_qname(path, name);
                if !symbols.contains_key(&key) {
                    // surely there's a better way to do this?
                    symbols.insert(
                        key,
                        Symbol::Variable {
                            name: name.lexeme.to_string(),
                            var_type: var_type.clone(),
                        },
                    );
                }
            }
            Statement::FunctionStmt { function } => {
                symbols.insert(
                    make_qname(path, &function.name),
                    Symbol::Function {
                        name: function.name.lexeme.to_string(),
                        parameters: function.parameters.to_vec(),
                        return_type: function.return_type.clone(),
                        body: function.body.to_vec(),
                    },
                );
            }
            Statement::ObjectStmt { name, fields } => {
                symbols.insert(
                    make_qname(path, name),
                    Symbol::Object {
                        name: name.lexeme.to_string(),
                        fields: fields.to_vec(),
                    },
                );
            }
            _ => {}
        }
    }
}

pub fn _add_types(
    path: &str,
    ast: &[Statement],
    symbols: &mut HashMap<String, Symbol>,
) -> Result<(), CompilerError> {
    for statement in ast {
        match statement {
            Statement::VarStmt {
                name,
                var_type,
                initializer,
            } => {
                let inferred_type = infer_type(initializer, symbols);
                let calculated_type = calculate_type(var_type, &inferred_type)?;
                let entry = symbols.get_mut(&format!("{}.{}", path, name.lexeme));
                if let Some(Symbol::Variable { var_type, .. }) = entry {
                    *var_type = calculated_type;
                }
            }
            _ => {}
        }
    }
    Ok(())
}

pub fn calculate_type(
    declared_type: &TokenType,
    inferred_type: &TokenType,
) -> Result<TokenType, CompilerError> {
    Ok(if declared_type != &Unknown {
        if declared_type != inferred_type {
            match (declared_type, inferred_type) {
                (I32, I64) => I32, //need this?
                (I32, Integer) => I32,
                (U32, I64) => U32,
                (U32, Integer) => U32,
                (F32, F64) => F32,
                (F32, FloatingPoint) => F32,
                (F64, I64) => F64,
                (F64, FloatingPoint) => F64,
                (U64, I64) => U64,
                (U64, I32) => U64,
                (I64, Integer) => I64,
                (StringType, _) => StringType, // meh, this all needs rigorous testing. Update: this is in progress
                _ => {
                    return Err(IncompatibleTypes(
                        declared_type.clone(),
                        inferred_type.clone(),
                    ));
                }
            }
        } else {
            declared_type.clone()
        }
    } else {
        match inferred_type {
            Integer | I64 => I64,
            FloatingPoint => F64,
            Bool => Bool,
            DateTime => DateTime,
            ListType => ListType,
            MapType => MapType,
            ObjectType(p) => ObjectType(p.clone()),
            _ => return Err(CompilerError::UnexpectedType(inferred_type.clone())),
        }
    })
}

pub fn infer_type(expr: &Expression, symbols: &HashMap<String, Symbol>) -> TokenType {
    match expr {
        Expression::Binary {
            left,
            operator,
            right,
            ..
        } => {
            let left_type = infer_type(left, symbols);
            let right_type = infer_type(right, symbols);
            if vec![Greater, Less, GreaterEqual, LessEqual].contains(&operator.token_type) {
                Bool
            } else if left_type == right_type {
                // map to determined numeric type if yet undetermined (32 or 64 bits)
                match left_type {
                    FloatingPoint => F64,
                    Integer => I64,
                    _ => left_type,
                }
            } else {
                if let Plus = operator.token_type {
                    // includes string concatenation with numbers
                    // followed by type coercion to 64 bits for numeric types
                    debug!("coerce {} : {}", left_type, right_type);
                    match (left_type, right_type) {
                        (_, StringType) => StringType,
                        (StringType, _) => StringType,
                        (FloatingPoint, _) => F64,
                        (Integer, FloatingPoint) => F64,
                        (Integer, _) => I64,
                        (I64, Integer) => I64,
                        (F64, _) => F64,
                        (U64, U32) => U64,
                        (I64, I32) => I64,
                        // could add a date and a duration. future work
                        // could add a List and a value. also future work
                        // could add a Map and a tuple. Will I add tuple types? Future work!
                        _ => panic!("Unexpected coercion"),
                    }
                    // could have done some fall through here, but this will fail less gracefully,
                    // so if my thinking is wrong or incomplete it will panic
                } else {
                    // type coercion to 64 bits for numeric types
                    debug!("coerce {} : {}", left_type, right_type);
                    match (left_type, right_type) {
                        (FloatingPoint, _) => F64,
                        (Integer, FloatingPoint) => F64,
                        (Integer, I64) => I64,
                        (I64, FloatingPoint) => F64,
                        (F64, _) => F64,
                        (U64, U32) => U64,
                        (I64, I32) => I64,
                        (I64, Integer) => I64,
                        _ => panic!("Unexpected coercion"),
                    }
                }
            }
        }
        Expression::Grouping { expression, .. } => infer_type(expression, symbols),
        Expression::Literal { literaltype, .. } => literaltype.clone(),
        Expression::List { literaltype, .. } => literaltype.clone(),
        Expression::Map { literaltype, .. } => literaltype.clone(),
        Expression::Unary {
            right, operator, ..
        } => {
            let literal_type = infer_type(right, symbols);
            if literal_type == Integer && operator.token_type == Minus {
                SignedInteger
            } else {
                UnsignedInteger
            }
        }
        Expression::Variable { var_type, .. } => var_type.clone(),
        Expression::FunctionCall { name, .. } => {
            let symbol = symbols.get(name);
            match symbol {
                Some(Symbol::Function { return_type, .. }) => return_type.clone(),
                Some(Symbol::Object { name, .. }) => ObjectType(name.clone()),
                _ => Unknown,
            }
        }
        Expression::MethodCall {
            receiver,
            ..
        } => infer_type(receiver, symbols),
        Expression::Stop { .. } => TokenType::Unknown,
        // Expression::PathMatch { .. } => TokenType::Unknown,
        Expression::NamedParameter { .. } => TokenType::Unknown,
        Expression::ListGet { .. } => TokenType::Unknown,
        Expression::MapGet { .. } => TokenType::Unknown,
        Expression::FieldGet { .. } => TokenType::Unknown,
    }
}