// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module parser

import (
	compiler2.scanner
	compiler2.ast
	compiler2.token
	compiler2.table
)

struct Parser {
	scanner &scanner.Scanner
mut:
	tok     token.Token
	lit     string
	//vars []string
	table &table.Table
}

pub fn parse_expr(text string, table &table.Table) ast.Expr {
	mut s := scanner.new_scanner(text)
	res := s.scan()
	mut p := Parser{
		scanner: s
		tok: res.tok
		lit: res.lit
		table: table
	}
	expr,_ := p.expr(token.lowest_prec)
	return expr
}

pub fn parse_file(text string, table &table.Table) ast.Program {
	s := scanner.new_scanner(text)
	mut exprs := []ast.Expr
	mut p := Parser{
		scanner: s
		//tok: res.tok
		//lit: res.lit
		table: table
	}
	p.next()
	for {
		//res := s.scan()
		if p.tok == .eof {
			break
		}
		println('expr at ' + p.tok.str())
		expr,_ := p.expr(token.lowest_prec)
		exprs << expr
		p.next()
	}
	println('nr exprs = $exprs.len')
	println(exprs[0])
	return ast.Program{exprs}
}

/*
pub fn parse_stmt(text string) ast.Stmt {
	mut s := scanner.new_scanner(text)
	res := s.scan()
	mut p := Parser{
		scanner: s
		tok: res.tok
		lit: res.lit
	}
	return p.stmt()
}
*/


fn (p mut Parser) next() {
	res := p.scanner.scan()
	p.tok = res.tok
	// println(p.tok.str())
	p.lit = res.lit
}

// Implementation of Pratt Precedence
pub fn (p mut Parser) expr(rbp int) (ast.Expr,ast.Type) {
	// null denotation (prefix)
	tok := p.tok
	lit := p.lit

	if p.tok == .name {
		name := p.lit
		p.next()
		if p.tok == .decl_assign {
			p.next()
			mut node := ast.Expr{}
			expr,t :=p.expr(token.lowest_prec)
			if name in p.table.names {
				verror('redefinition of `$name`')
			}
			p.table.names << name
			println(p.table.names)
			println('added $name')
			// TODO can't return VarDecl{}
			node = ast.VarDecl{
				name: name
				expr: expr//p.expr(token.lowest_prec)
				typ: t
			}//, ast.void_type
			return node, ast.void_type
		}
	} else {
		p.next()
	}
	mut node := ast.Expr{}
	mut typ := ast.void_type
	match tok {
		.lpar {
			node,typ = p.expr(0)
			if p.tok != .rpar {
				panic('Parse Error: expected )')
			}
			p.next()
		}
		else {
			// TODO: fix bug. note odd conditon instead of else if (same below)
			if tok.is_scalar() {
				if tok == .str {
					node = ast.StringLiteral{
						val: lit
					}
					typ = ast.string_type
				}
				if tok == .number {
					node = ast.IntegerLiteral{
						val: lit.int()
					}
					typ = ast.int_type
				}
				// else {
				// verror('bad scalar token')
				// }
			}
			if !tok.is_scalar() && tok.is_unary() {
				expr,_ := p.expr(token.highest_prec)
				node = ast.UnaryExpr{
					// left: p.expr(token.highest_prec)
					left: expr
					op: tok
				}
			}
		}
	}
	// left binding power
	for rbp < p.tok.precedence() {
		tok2 := p.tok
		p.next()
		//mut t1 := ast.Type{}
		mut t2 := ast.Type{}
		//mut q := false
		// left denotation (infix)
		if tok2.is_right_assoc() {
			//q = true
			mut expr := ast.Expr{}
			expr,t2 = p.expr(tok2.precedence() - 1)
			node = ast.BinaryExpr{
				left: node
				//left_type: t1
				op: tok2
				// right: p.expr(tok2.precedence() - 1)

				right: expr

			}
			if typ.name != t2.name {
				println('bad types $typ.name $t2.name')
			}
		}
		if !tok2.is_right_assoc() && tok2.is_left_assoc() {
			mut expr := ast.Expr{}
			expr,t2 = p.expr(tok2.precedence())
			node = ast.BinaryExpr{
				left: node
				op: tok2
				right: expr
			}
		}
	}
	return node,typ
}

/*
fn (p mut Parser) stmt() ast.Stmt {
	if p.tok == .name {
		name := p.lit
		p.next()
		if p.tok == .decl_assign {
			p.next()
			return ast.VarDecl{
				name: name
				expr: p.expr(token.lowest_prec)
			}
		}
	}
	/*
	match node {
		Ident {


		}

	}
	*/

	return ast.VarDecl{}
}
*/


fn verror(s string) {
	println(s)
	exit(1)
}