package mishmash

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	"testing"
	"time"
)

const The32BitHashesFilename = "cppmishmash32.txt"

type WordWithHashString struct {
	word, hash string
}

func ParseHashesFile(filename string) ([]WordWithHashString, error) {
	f, err := os.Open(filename)
	if err != nil {
		return nil, fmt.Errorf("error opening %s: %w", filename, err)
	}
	defer f.Close()
	scanner := bufio.NewScanner(f)
	results := make([]WordWithHashString, 0)
	lineNumber := 0
	for scanner.Scan() {
		lineNumber++
		line := strings.TrimSpace(scanner.Text())
		if len(line) == 0 {
			continue
		}
		fields := strings.Fields(line)
		if len(fields) != 2 {
			return nil, fmt.Errorf("error: malformed line %s at line %d", line, lineNumber)
		}
		results = append(results, WordWithHashString{fields[0], fields[1]})
	}
	return results, nil
}

func TestAgainstCppMishmash32(t *testing.T) {
	wordsWithHashes, err := ParseHashesFile(The32BitHashesFilename)
	if err != nil {
		t.Fatalf("error: %v\n", err)
	}
	start := time.Now()
	for _, obj := range wordsWithHashes {
		word, hashString := obj.word, obj.hash
		want, err := strconv.ParseUint(hashString, 16, 32)
		if err != nil {
			t.Fatalf("error parsing %+v: %v\n", obj, err)
		}
		hasher := Mishmash32{}
		hasher.Write([]byte(word))
		got := hasher.Sum32()
		if uint32(want) != got {
			t.Fatalf("error for %q: wanted %08x; got %08x\n", word, want, got)
		}
	}
	fmt.Printf("finished testing %d words after %s\n", len(wordsWithHashes), time.Since(start))
}