package token

import (
	"fmt"

	"git.maximhutz.com/max/lambda/pkg/iterator"
)

// ParseRawToken consumes the next token from the iterator if its type matches
// the expected type.
// Uses [iterator.Try] for automatic backtracking on failure.
func ParseRawToken[T Type](i *iterator.Iterator[Token[T]], expected T) (*Token[T], error) {
	return iterator.Try(i, func(i *iterator.Iterator[Token[T]]) (*Token[T], error) {
		if tok, err := i.Next(); err != nil {
			return nil, err
		} else if tok.Type != expected {
			return nil, fmt.Errorf("expected token %v, got %v'", expected.Name(), tok.Value)
		} else {
			return &tok, nil
		}
	})
}

// ParseList repeatedly applies a parse function, collecting results into a
// slice.
// Stops when the parse function returns an error.
// Returns an error if fewer than minimum results are collected.
func ParseList[T Type, U any](i *iterator.Iterator[Token[T]], fn func(*iterator.Iterator[Token[T]]) (U, error), minimum int) ([]U, error) {
	results := []U{}

	for {
		if u, err := fn(i); err != nil {
			if len(results) < minimum {
				return nil, fmt.Errorf("expected at least '%v' items, got only '%v': %w", minimum, len(results), err)
			}
			return results, nil
		} else {
			results = append(results, u)
		}
	}
}