import std/[strutils, strformat]

from ../token import Token, TokenKind
from ast import ASTNodeKind, ASTNode, printNode
import ../error_reporting

type Parser* = object
    pos: int
    tokens: seq[Token]

    tree: ASTNode

func initParser*(tokens: seq[Token]): Parser = Parser(pos: 0, tokens: tokens)

# Helpers
func atEnd*(parser: Parser): bool = parser.pos >= parser.tokens.len

func advance*(parser: var Parser): Token =
    if not parser.atEnd:
        result = parser.tokens[parser.pos]

    parser.pos += 1

func peek*(parser: Parser): Token =
    if not parser.atEnd:
        result = parser.tokens[parser.pos]

func prev*(parser: Parser): Token = parser.tokens[parser.pos - 1]

func match*(parser: var Parser, tk: TokenKind): bool =
    if not parser.atEnd and parser.peek.kind == tk:
        discard parser.advance()
        result = true

func consume*(parser: var Parser, tk: TokenKind, msg: string): Token =
    ## Attempt to consume a token of the given kind, and raise an error if
    ## we cannot for whatever reason
    if not parser.atEnd and parser.peek.kind == tk:
        result = parser.advance()

    raise parserError(parser.pos, parser.peek.kind, msg)