package diff

import (
	"fmt"
	"strings"

	"github.com/peter-evans/patience"
)

// 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
}

// typeSymbol returns the associated symbol of a DiffType.
func typeSymbol(t patience.DiffType) string {
	switch t {
	case patience.Equal:
		return "  "
	case patience.Insert:
		return "+ "
	case patience.Delete:
		return "- "
	default:
		panic("unknown DiffType")
	}
}

// DiffText returns the source and destination texts (all equalities, insertions and deletions).
func DiffText(diffs []patience.DiffLine) string {
	s := make([]string, len(diffs))
	for i, l := range diffs {
		s[i] = fmt.Sprintf("%s%s", typeSymbol(l.Type), l.Text)
	}
	return strings.Join(s, "\n")
}