package settings

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"maps"
	"math/rand"
	"testing"
)

var (
	KeyValuePairs = map[string]string{
		"A": "a",
		"B": "b",
		"C": "c",
	}
)

func RandomKeyValueDelimiter() byte {
	return KeyValueDelimiterChars[rand.Intn(len(KeyValueDelimiterChars))]
}

func WriteMapToWriter(w io.Writer, m map[string]string) error {
	writer := bufio.NewWriter(w)
	comments := []string{"// this is a random comment", "# this is another random comment"}
	randomComment := func() string { return comments[rand.Intn(len(comments))] }
	var position int
	for k, v := range m {
		switch rand.Float64() >= .5 {
		case true:
			fmt.Fprintf(writer, "%s\n", randomComment())
		}
		fmt.Fprintf(writer, "%s%c%s", k, RandomKeyValueDelimiter(), v)
		if position < len(m)-1 {
			writer.WriteByte('\n')
		}
		position++
	}
	return writer.Flush()
}

func TestScannerParsesFilesProperly(t *testing.T) {
	var buffer bytes.Buffer
	err := WriteMapToWriter(&buffer, KeyValuePairs)
	if err != nil {
		t.Fatalf("error writing map to buffer: %v\n", err)
	}
	scanner := NewScanner(&buffer)
	got := make(map[string]string)
loop:
	for {
		key, value, err := scanner.ReadNextLine()
		if err != nil {
			if errors.Is(err, io.EOF) {
				break loop
			}
			t.Fatalf("error reading next line from scanner: %v\n", err)
		}
		got[key] = value
	}
	if want := KeyValuePairs; !maps.Equal(want, got) {
		t.Fatalf("error: wanted '%+v'; got '%+v'\n", want, got)
	}
}

func TestScannerHandlesInvalidLinesProperly(t *testing.T) {
	buffer := bytes.NewBufferString("validKey-validValue")
	scanner := NewScanner(buffer)
	key, value, err := scanner.ReadNextLine()
	if !errors.Is(err, ErrNoValidDelimiter) {
		t.Fatalf("error: wanted %v; got %v\n", ErrNoValidDelimiter, err)
	} else if want, got := "", key; want != got {
		t.Fatalf("error: wanted key '%s'; got '%s'\n", want, got)
	} else if want, got := "", value; want != got {
		t.Fatalf("error: wanted value '%s'; got '%s'\n", want, got)
	}
}