package parser

import (
	"fmt"
	"jinx/pkg/lang/ast"
	"jinx/pkg/lang/scanner/token"
)

func (p *Parser) parseStmt() (ast.Stmt, error) {
	switch p.peek().Kind {
	case token.KwUse:
		return p.parseUseStmt()
	case token.KwFn:
		return p.parseFnDeclStmt()
	case token.KwObject:
		return p.parseObjectDeclStmt()
	case token.KwVar:
		return p.parseVarDeclStmt()
	case token.KwIf:
		return p.parseIfStmt()
	case token.KwTry:
		return p.parseTryStmt()
	case token.KwReturn:
		return p.parseReturnStmt()
	case token.KwContinue:
		return p.parseContinueStmt()
	case token.KwBreak:
		return p.parseBreakStmt()
	case token.KwThrow:
		return p.parseThrowStmt()
	default:
		if p.peek().CanEndStmt() {
			return p.parseEmptyStmt()
		} else {
			return p.parseExprStmt()
		}
	}
}

func (p *Parser) parseUseStmt() (ast.Stmt, error) {
	panic("not implemented")
}

func (p *Parser) parseFnDeclStmt() (ast.Stmt, error) {
	fnTok, err := p.expect(token.KwFn)
	if err != nil {
		return ast.Stmt{}, err
	}

	name, err := p.parseIdent()
	if err != nil {
		return ast.Stmt{}, err
	}

	params, err := p.parseFnParams()
	if err != nil {
		return ast.Stmt{}, err
	}

	block, err := p.parseBlock()
	if err != nil {
		return ast.Stmt{}, err
	}

	return ast.Stmt{
		At:   fnTok.At,
		Kind: ast.StmtKindFnDecl,
		Value: ast.StmtFnDecl{
			Name: name,
			Args: params,
			Body: block,
		},
	}, nil
}

func (p *Parser) parseFnParams() ([]ast.IdentNode, error) {
	// FnParams = "(" ( IDENT ("," IDENT)* )? ")"

	if _, err := p.expect(token.LParen); err != nil {
		return nil, err
	}

	params := []ast.IdentNode{}

	if p.peek().Kind != token.RParen {
		for {
			param, err := p.parseIdent()
			if err != nil {
				return nil, err
			}

			params = append(params, param)

			if p.peek().Kind == token.RParen {
				break
			}

			if _, err := p.expect(token.Comma); err != nil {
				return nil, err
			}
		}
	}

	if _, err := p.expect(token.RParen); err != nil {
		return nil, err
	}

	return params, nil
}

func (p *Parser) parseObjectDeclStmt() (ast.Stmt, error) {
	panic("not implemented")
}

func (p *Parser) parseVarDeclStmt() (ast.Stmt, error) {
	// VarDeclStmt = "var" IDENT "=" Expr

	varTok, err := p.expect(token.KwVar)
	if err != nil {
		return ast.Stmt{}, err
	}

	name, err := p.parseIdent()
	if err != nil {
		return ast.Stmt{}, err
	}

	if _, err := p.expect(token.Assign); err != nil {
		return ast.Stmt{}, err
	}

	expr, err := p.parseExpr()
	if err != nil {
		return ast.Stmt{}, err
	}

	return ast.Stmt{
		At:   varTok.At,
		Kind: ast.StmtKindVarDecl,
		Value: ast.StmtVarDecl{
			Name:  name,
			Value: expr,
		},
	}, nil
}

func (p *Parser) parseIfStmt() (ast.Stmt, error) {
	// IfStmt = "if" Expr Block ("elif" Expr Block)* ("else" Block)?
	ifTok, err := p.expect(token.KwIf)
	if err != nil {
		return ast.Stmt{}, err
	}

	cond, err := p.parseExpr()
	if err != nil {
		return ast.Stmt{}, err
	}

	then, err := p.parseBlock()
	if err != nil {
		return ast.Stmt{}, err
	}

	elifs := []ast.CondNode{}

	for p.peek().Kind == token.KwElif {
		elifTok, err := p.expect(token.KwElif)
		if err != nil {
			return ast.Stmt{}, err
		}

		elifCond, err := p.parseExpr()
		if err != nil {
			return ast.Stmt{}, err
		}

		elifThen, err := p.parseBlock()
		if err != nil {
			return ast.Stmt{}, err
		}

		elifs = append(elifs, ast.CondNode{
			At:   elifTok.At,
			Cond: elifCond,
			Then: elifThen,
		})
	}

	elseThen := ast.BlockNode{}

	if p.peek().Kind == token.KwElse {
		_, err := p.expect(token.KwElse)
		if err != nil {
			return ast.Stmt{}, err
		}

		elseThen, err = p.parseBlock()
		if err != nil {
			return ast.Stmt{}, err
		}
	}

	return ast.Stmt{
		At:   ifTok.At,
		Kind: ast.StmtKindIf,
		Value: ast.StmtIf{
			Cond:  cond,
			Then:  then,
			Elifs: elifs,
			Else:  elseThen,
		},
	}, nil
}

func (p *Parser) parseTryStmt() (ast.Stmt, error) {
	// TryStmt = "try" Block "catch" Ident ("finally" Block)?

	tryTok, err := p.expect(token.KwTry)
	if err != nil {
		return ast.Stmt{}, err
	}

	tryBlock, err := p.parseBlock()
	if err != nil {
		return ast.Stmt{}, err
	}

	if _, err = p.expect(token.KwCatch); err != nil {
		return ast.Stmt{}, err
	}

	catchName, err := p.parseIdent()
	if err != nil {
		return ast.Stmt{}, err
	}

	catchBlock, err := p.parseBlock()
	if err != nil {
		return ast.Stmt{}, err
	}

	finallyBlock := ast.BlockNode{}
	if p.peek().Kind == token.KwFinally {
		_, err := p.expect(token.KwFinally)
		if err != nil {
			return ast.Stmt{}, err
		}

		finallyBlock, err = p.parseBlock()
		if err != nil {
			return ast.Stmt{}, err
		}
	}

	return ast.Stmt{
		At:   tryTok.At,
		Kind: ast.StmtKindTry,
		Value: ast.StmtTry{
			Try:         tryBlock,
			CatchedName: catchName,
			Catch:       catchBlock,
			Finally:     finallyBlock,
		},
	}, nil
}

func (p *Parser) parseReturnStmt() (ast.Stmt, error) {
	// ReturnStmt = "return" (Expr)?
	returnTok, err := p.expect(token.KwReturn)
	if err != nil {
		return ast.Stmt{}, err
	}

	expr := ast.Expr{}
	if !p.peek().CanEndStmt() {
		expr, err = p.parseExpr()
		if err != nil {
			return ast.Stmt{}, err
		}
	}

	return ast.Stmt{
		At:   returnTok.At,
		Kind: ast.StmtKindReturn,
		Value: ast.StmtReturn{
			Value: expr,
		},
	}, nil
}

func (p *Parser) parseContinueStmt() (ast.Stmt, error) {
	// ContinueStmt = "continue"
	continueTok, err := p.expect(token.KwContinue)
	if err != nil {
		return ast.Stmt{}, err
	}

	return ast.Stmt{
		At:    continueTok.At,
		Kind:  ast.StmtKindContinue,
		Value: ast.StmtContinue{},
	}, nil
}

func (p *Parser) parseBreakStmt() (ast.Stmt, error) {
	// BreakStmt = "break"

	breakTok, err := p.expect(token.KwBreak)
	if err != nil {
		return ast.Stmt{}, err
	}

	return ast.Stmt{
		At:    breakTok.At,
		Kind:  ast.StmtKindBreak,
		Value: ast.StmtBreak{},
	}, nil
}

func (p *Parser) parseThrowStmt() (ast.Stmt, error) {
	// ThrowStmt = "throw" Expr

	throwTok, err := p.expect(token.KwThrow)
	if err != nil {
		return ast.Stmt{}, err
	}

	expr, err := p.parseExpr()
	if err != nil {
		return ast.Stmt{}, err
	}

	return ast.Stmt{
		At:   throwTok.At,
		Kind: ast.StmtKindThrow,
		Value: ast.StmtThrow{
			Value: expr,
		},
	}, nil
}

func (p *Parser) parseExprStmt() (ast.Stmt, error) {
	expr, err := p.parseExpr()
	if err != nil {
		return ast.Stmt{}, err
	}

	return ast.Stmt{
		At:   expr.At,
		Kind: ast.StmtKindExpr,
		Value: ast.StmtExpr{
			Value: expr,
		},
	}, nil
}

func (p *Parser) parseEmptyStmt() (ast.Stmt, error) {
	return ast.Stmt{
		At:    p.peek().At,
		Kind:  ast.StmtKindEmpty,
		Value: ast.StmtEmpty{},
	}, nil
}

func (p *Parser) parseStmtEnd() error {
	tok := p.peek()
	if !tok.CanEndStmt() {
		panic(fmt.Errorf("wanted statement end, received: %+v", tok))
	}
	p.next()
	return nil
}