use std::{collections::{BTreeMap, BTreeSet}, result, vec};

use crate::{ast::types::{BlockStmt, CompileUnit, Expr, FuncDeclStmt, GlobalDeclStmt, ReturnStmt, Statement, VarDeclStmt}, diagnostic::Diagnositics, ir::{err::IRError, types::{BinaryOp, Function, IRInstr, IRType, MoveRValue, Variable, VariableType}}};

pub struct Generator {
    var_manager: VariableManager,
    function_map: BTreeMap<String, Function>,
    current_func_return_type: Option<IRType>,
    diagnostic: Diagnositics,
}

impl Generator {
    pub fn new() -> Self {
        let mut function_map = BTreeMap::new();
        function_map.insert("putint".to_string(), Function {
            name: "putint".to_string(),
            parameter_types: vec![IRType::I32],
            return_type: IRType::Void,
        });
        Self {
            var_manager: VariableManager::new(),
            current_func_return_type: None,
            diagnostic: Diagnositics::new(),
            function_map,
        }
    }

    pub fn emit(&mut self, compile_unit: CompileUnit) -> Vec<IRInstr> {
        self.generate_compile_unit(compile_unit)
    }

    fn generate_compile_unit(&mut self, compile_unit: CompileUnit) -> Vec<IRInstr> {
        let mut instrs = vec![];
        use GlobalDeclStmt::*;
        for decl in compile_unit.global_decls {
            match decl {
                VarDecl(var_decl) => {
                    instrs.extend(self.generate_var_decl(var_decl, true));
                }
                FuncDecl(func_decl) => {
                    instrs.extend(self.generate_func_decl(func_decl));
                }
            }
        }
        instrs
    }

    fn generate_var_decl(&mut self, var_decl: VarDeclStmt, is_global: bool) -> Vec<IRInstr> {
        let mut instrs = vec![];
        let var_type = if is_global { VariableType::Global } else { VariableType::Local };
        for value in var_decl.values {
            match self.var_manager.declare_variable(&value.name, var_type, value.var_type.into()) {
                Ok(var) => {
                    if is_global { instrs.push(IRInstr::Declare(var)); }
                }
                Err(e) => {
                    self.diagnostic.add_from_ir_error(e, value.span);
                }
            }
        }

        instrs
    }

    fn generate_func_decl(&mut self, func_decl: FuncDeclStmt) -> Vec<IRInstr> {
        if self.function_map.contains_key(&func_decl.name) {
            self.diagnostic.add_from_ir_error(IRError::FunctionHasBeenDefined(func_decl.name.clone()), func_decl.span);
            return vec![];
        }
        self.current_func_return_type = Some(func_decl.return_type.into());
        self.var_manager.enter_scope();
        let parameters: Vec<Variable> =  match func_decl.params.iter().map(|param| {
            match self.var_manager.declare_variable(&param.name, VariableType::Local, param.param_type.into()) {
                Ok(var) => Ok(var),
                Err(e) => {
                    self.diagnostic.add_from_ir_error(e, param.span);
                    Err(())
                }
            }
        }).collect() {
            Ok(p) => p,
            Err(()) => return vec![],
        };
        let temp_parameters = parameters.iter().map(|param| self.var_manager.declare_param_temp(param.data_type)).collect::<Vec<_>>();
        let mut body_instrs = vec![];
        let block_instrs = self.generate_block_stmt(func_decl.body);
        for var in self.var_manager.get_cur_func_variables() {
            if matches!(var.var_type, VariableType::ParamTemp) {
                continue;
            }
            body_instrs.push(IRInstr::Declare(var));
        }
        body_instrs.push(IRInstr::Entry);
        parameters.iter().zip(temp_parameters.iter()).for_each(|(param, temp_param)| {
            body_instrs.push(IRInstr::Move(*temp_param, MoveRValue::Var(*param)));
        });
        body_instrs.extend(block_instrs);

        self.var_manager.exit_scope();
        self.current_func_return_type = None;
        self.var_manager.clear_local_counter();
        let func  = Function {
            name: func_decl.name,
            parameter_types: temp_parameters.iter().map(|v| v.data_type).collect(),
            return_type: func_decl.return_type.into(),
        };
        self.function_map.insert(func.name.clone(), func.clone());
        vec![IRInstr::DefineFunc(func, parameters, body_instrs)]
    }
    fn generate_block_stmt(&mut self, block_stmt: BlockStmt) -> Vec<IRInstr> {
        let mut instrs = vec![];
        for stmt in block_stmt.statements {
            instrs.extend(self.generate_statement(stmt));
        }
        instrs
    }

    fn generate_statement(&mut self, stmt: Statement) -> Vec<IRInstr> {
        use Statement::*;
        let instrs = match stmt {
            Return(return_stmt) => self.generate_return_stmt(return_stmt),
            Block(block_stmt) => {
                self.var_manager.enter_scope();
                let block_instrs = self.generate_block_stmt(block_stmt);
                self.var_manager.exit_scope();
                block_instrs
            },
            Expr(expr) => self.generate_expr(expr).0,
            VarDecl(var_decl) => self.generate_var_decl(var_decl, false),
        };
        instrs
    }

    fn generate_return_stmt(&mut self, return_stmt: ReturnStmt) -> Vec<IRInstr> {
        let mut instrs = vec![];
        match return_stmt.value {
            Some(expr) => {
                let (value_instrs, value_var) = self.generate_expr(expr);
                instrs.extend(value_instrs);
                if value_var.is_some() {
                    instrs.push(IRInstr::Exit(value_var));
                }
            }
            None => instrs.push(IRInstr::Exit(None)),
        }
        instrs
    }

    fn generate_expr(&mut self, expr: Expr) -> (Vec<IRInstr>, Option<Variable>) {
        use crate::ast::types::ExprValue;
        match expr.value {
            ExprValue::IntLit(i) => {
                // TODO: convert check
                let var = self.var_manager.declare_temp(IRType::I32);
                (vec![IRInstr::Move(var, MoveRValue::ConstInt(i as i32))], Some(var))
            },
            ExprValue::Var(name) => {
                if let Some(var) = self.var_manager.get_variable(&name) {
                    (vec![], Some(var))
                } else {
                    self.diagnostic.add_from_ir_error(IRError::VariableNotFound(name.clone()), expr.span);
                    (vec![], None)
                }
            },
            ExprValue::Assign { lvalue, rvalue } => {
                // TODO: only support simple variable assignment now, need to support more complex lvalue in the future
                if let ExprValue::Var(name) = lvalue.value {
                    let var = match self.var_manager.get_variable(&name) {
                        Some(var) => var,
                        None => {
                            self.diagnostic.add_from_ir_error(IRError::VariableNotFound(name.clone()), lvalue.span);
                            return (vec![], None);
                        }
                    };
                    let (mut instrs, rvalue_var) = self.generate_expr(*rvalue);
                    if rvalue_var.is_none() {
                        return (vec![], None);
                    }
                    let rvalue_var = rvalue_var.unwrap();
                    if var.data_type != rvalue_var.data_type {
                        self.diagnostic.add_from_ir_error(IRError::TypeMismatch(var.data_type, rvalue_var.data_type), lvalue.span);
                        return (vec![], None);
                    }
                    instrs.push(IRInstr::Move(var, MoveRValue::Var(rvalue_var)));
                    let temp_var = self.var_manager.declare_temp(var.data_type);
                    instrs.push(IRInstr::Move(temp_var, MoveRValue::Var(var)));
                    (instrs, Some(temp_var))
                } else {
                    self.diagnostic.add_from_ir_error(IRError::InvalidAssignmentTarget, lvalue.span);
                    return (vec![], None);
                }
            },
            ExprValue::BinaryOp { lhs, op, rhs } => {
                let lhs_span = lhs.span;
                let rhs_span = rhs.span;
                let (mut instrs, left_var) = self.generate_expr(*lhs);
                if left_var.is_none() {
                    return (vec![], None);
                }
                let left_var = left_var.unwrap();
                let (right_instrs, right_var) = self.generate_expr(*rhs);
                if right_var.is_none() {
                    return (vec![], None);
                }
                let right_var = right_var.unwrap();
                instrs.extend(right_instrs);
                let mut has_void = false;
                if matches!(left_var.data_type, IRType::Void) {
                    self.diagnostic.add_from_ir_error(IRError::InvalidOperand(IRType::Void), lhs_span);
                    has_void = true;
                }
                if matches!(right_var.data_type, IRType::Void) {
                    self.diagnostic.add_from_ir_error(IRError::InvalidOperand(IRType::Void), rhs_span);
                    has_void = true;
                }
                if has_void {
                    return (vec![], None);
                }
                if left_var.data_type != right_var.data_type {
                    self.diagnostic.add_from_ir_error(IRError::IncompatiableOperand(left_var.data_type, right_var.data_type), lhs_span);
                    self.diagnostic.add_from_ir_error(IRError::InvalidOperand(left_var.data_type), rhs_span);
                    return (vec![], None);
                }
                let result_type;
                match Into::<BinaryOp>::into(op) {
                    BinaryOp::Add | BinaryOp::Sub | BinaryOp::Mul | BinaryOp::Div | BinaryOp::Mod => {
                        result_type = left_var.data_type;
                    },
                    BinaryOp::Eq | BinaryOp::Ne | BinaryOp::Lt | BinaryOp::Gt | BinaryOp::Le | BinaryOp::Ge => {
                        result_type = IRType::I1;
                    }
                }
                let dest_var = self.var_manager.declare_temp(result_type);
                instrs.push(IRInstr::Binary(dest_var, left_var, op.into(), right_var));
                (instrs, Some(dest_var))
            },
            ExprValue::FuncCall(func_name, args) => {
                let mut instrs = vec![];
                let mut arg_vars = vec![];
                let func_def = if let Some(func_def) = self.function_map.get(&func_name) {
                    func_def
                } else {
                    self.diagnostic.add_from_ir_error(IRError::FunctionNotFound(func_name.clone()), expr.span);
                    return (vec![], None);
                }.clone();
                if args.len() < func_def.parameter_types.len() {
                    self.diagnostic.add_from_ir_error(IRError::TooFewArguments(func_def.parameter_types.len(), args.len()), expr.span);
                    return (vec![], None);
                }
                if args.len() > func_def.parameter_types.len() {
                    self.diagnostic.add_from_ir_error(IRError::TooManyArguments(func_def.parameter_types.len(), args.len()), expr.span);
                    return (vec![], None);
                }
                let mut has_error = false;
                for (i, arg) in args.into_iter().enumerate() {
                    let (arg_instrs, arg_var) = self.generate_expr(arg);
                    if arg_var.is_none() {
                        has_error = true;
                        continue;
                    }
                    let arg_var = arg_var.unwrap();
                    let parameter_type = func_def.parameter_types.get(i).unwrap();
                    if *parameter_type != arg_var.data_type {
                        self.diagnostic.add_from_ir_error(IRError::TypeMismatch(*parameter_type, arg_var.data_type), expr.span);
                        has_error = true;
                        continue;
                    }
                    instrs.extend(arg_instrs);
                    arg_vars.push(arg_var);
                }
                if has_error {
                    return (vec![], None);
                }
                let ret_variable = if matches!(func_def.return_type, IRType::Void) {
                    None
                } else {
                    Some(self.var_manager.declare_temp(func_def.return_type))
                };
                instrs.push(IRInstr::FuncCall(func_def.clone(), arg_vars, ret_variable));
                (instrs, ret_variable)
            }
        }
    }
}

struct VariableManager {
    variable_map: BTreeMap<String, Vec<Variable>>,
    scopes: Vec<BTreeSet<String>>,
    global_counter: usize,
    local_counter: usize,
    local_var_type: Vec<Variable>,
}

impl VariableManager {
    pub fn new() -> Self {
        Self {
            variable_map: BTreeMap::new(),
            scopes: vec![BTreeSet::new()],
            global_counter: 0,
            local_counter: 0,
            local_var_type: vec![],
        }
    }
    pub fn enter_scope(&mut self) {
        self.scopes.push(BTreeSet::new());
    }

    pub fn exit_scope(&mut self) {
        let variables = self.scopes.pop().unwrap();
        for var in variables {
            self.variable_map.get_mut(&var).unwrap().pop();
        }
    }

    fn declare_variable(&mut self, name: &str, var_type: VariableType, var_data_type: IRType) -> Result<Variable, IRError> {
        if self.scopes.last().unwrap().contains(name) {
            return Err(IRError::VariableHasBeenDefined(name.to_string()));
        }
        let variable = match var_type {
            VariableType::Global => {
                let var = Variable { index: self.global_counter, var_type, data_type: var_data_type };
                self.global_counter += 1;
                var
            }
            VariableType::Local => {
                let var = Variable { index: self.local_counter, var_type, data_type: var_data_type };
                self.local_counter += 1;
                var
            }
            _ => unreachable!(),
        };
        self.variable_map.entry(name.to_string()).or_default().push(variable);
        self.scopes.last_mut().unwrap().insert(name.to_string());
        if matches!(var_type, VariableType::Local) {
            self.local_var_type.push(variable);
        }
        Ok(variable)
    }
    pub fn declare_gloabal(&mut self, name: &str, var_data_type: IRType) -> Result<Variable, IRError> {
        self.declare_variable(name, VariableType::Global, var_data_type)
    }
    pub fn declare_local(&mut self, name: &str, var_data_type: IRType) -> Result<Variable, IRError> {
        self.declare_variable(name, VariableType::Local, var_data_type)
    }
    pub fn declare_temp(&mut self, var_data_type: IRType) -> Variable {
        let var = Variable { index: self.local_counter, var_type: VariableType::Temp, data_type: var_data_type };
        self.local_counter += 1;
        self.local_var_type.push(var);
        var
    }
    pub fn declare_param_temp(&mut self, var_data_type: IRType) -> Variable {
        let var = Variable { index: self.local_counter, var_type: VariableType::ParamTemp, data_type: var_data_type };
        self.local_counter += 1;
        self.local_var_type.push(var);
        var
    }
    pub fn clear_local_counter(&mut self) {
        self.local_counter = 0;
        self.local_var_type.clear();
    }
    pub fn get_cur_func_variables(&self) -> Vec<Variable> {
        self.local_var_type.iter().cloned().collect()
    }
    pub fn get_variable(&self, name: &str) -> Option<Variable> {
        self.variable_map.get(name).and_then(|vars| vars.last()).cloned()
    }

}

#[cfg(test)]
mod tests {
    use std::io::BufRead;
    use std::path::Path;
    use std::fs::File;
    use crate::ast::graph::AstGraphExt;
    use std::io::Write;
    use crate::frontend::lexer::Lexer;
    use crate::frontend::parser::Parser;
    use crate::utils::case_list::CaseList;
    use crate::utils::num_sequence::NumberSequence;

    pub use super::*;
    fn test_case(case_str: &str) {
        let case_sequence = NumberSequence::from_str(case_str).unwrap();
        let case_list = CaseList::from_dir(&Path::new("./testcases")).unwrap();
        let mut error_case_cnt = 0;
        for case_no in case_sequence {
            let case_path = case_list.get_case_path(case_no).unwrap();
            println!("{}", case_path.display());
            let file = File::open(&case_path).unwrap();
            let mut buf_reader = std::io::BufReader::new(file);
            let mut lexer = Lexer::new();
            let mut full_text = String::new();
            loop {
                let mut line = String::new();
                let bytes_read = buf_reader.read_line(&mut line).unwrap();
                if bytes_read == 0 {
                    break;
                }
                full_text.push_str(&line);
                lexer.parse_next_str(&line);
            }
            let (tokens, diagnostics) = lexer.finish();
            let mut is_error = false;
            if !diagnostics.is_empty() {
                diagnostics.print(&format!("{}", case_path.display()), &full_text);
                is_error = true;
            }
            let mut parser = Parser::new(tokens, diagnostics);
            let compile_unit = parser.parse();
            let case_name = case_list.get_case_name(case_no).unwrap().strip_suffix(".c").unwrap();
            if !parser.diagnostics.is_empty() {
                parser.diagnostics.print(&format!("{}", case_path.display()), &full_text);
                is_error = true;
            }
            let mut generator = Generator::new();
            let ir = generator.emit(compile_unit);
            if !generator.diagnostic.is_empty() {
                generator.diagnostic.print(&format!("{}", case_path.display()), &full_text);
                is_error = true;
            }
            let mut ir_file = File::create(format!("output/{}.ir", case_name)).unwrap();
            for instr in ir {
                writeln!(ir_file, "{}", instr).unwrap();
            }
            if is_error {
                error_case_cnt += 1;
            }
        }
        if error_case_cnt > 0 {
            panic!("Found {} cases with errors", error_case_cnt);
        }

    }
    #[test]
    fn test_expr() {
        test_case("0-3,14-25");
        // test_case("0-3,14-25");
    }
}