package diff

import (
	"fmt"
	"strings"
)

// compareStrings compares two strings character by character, optionally ignoring whitespace.
func compareStrings(str1, str2 string, compareSpace bool) bool {
	if compareSpace {
		return str1 == str2
	}
	var i, j int
	l1 := len(str1)
	l2 := len(str2)
	for i < l1 && j < l2 {
		for i < l1 && isWhitespace(str1[i]) {
			i++
		}
		for j < l2 && isWhitespace(str2[j]) {
			j++
		}
		if i < l1 && j < l2 && str1[i] != str2[j] {
			return false
		}
		if i < l1 {
			i++
		}
		if j < l2 {
			j++
		}
	}
	for i < l1 && isWhitespace(str1[i]) {
		i++
	}
	for j < l2 && isWhitespace(str2[j]) {
		j++
	}
	return i == l1 && j == l2
}

func isWhitespace(b byte) bool {
	return b == ' ' ||
		b == '\t' ||
		b == '\n' ||
		b == '\r' ||
		b == '\v' ||
		b == '\f' ||
		b == 0x85 ||
		b == 0xA0
}

func formatDiff(oldList []string, newList []string, ops []Op) string {
	var result []string
	i, j := 0, 0
	for _, op := range ops {
		if op.OpType == OpDelete {
			for i < op.OldPos {
				result = append(result, "  "+oldList[i])
				i++
				j++
			}
			result = append(result, "- "+fmt.Sprint(op.Elem))
			i++
		} else if op.OpType == OpInsert {
			for j < op.NewPos {
				result = append(result, "  "+newList[j])
				i++
				j++
			}
			result = append(result, "+ "+fmt.Sprint(op.Elem))
			j++
		}
	}
	for i < len(oldList) && j < len(newList) {
		result = append(result, "  "+oldList[i])
		i++
		j++
	}
	return strings.Join(result, "\n")
}