package classes

import (
	"errors"
	"math/rand"
	"strings"
	"testing"
)

// robotsCombinations enumerates every combination of the C5 grammar's
// directives (with representative arguments).
func robotsCombinations() []Robots {
	ptr := func(n int) *int { return &n }
	var out []Robots
	for _, index := range []string{"", "index", "noindex"} {
		for _, follow := range []string{"", "follow", "nofollow"} {
			for flags := 0; flags < 8; flags++ {
				for _, snippet := range []*int{nil, ptr(-1), ptr(0), ptr(160)} {
					for _, image := range []string{"", "none", "standard", "large"} {
						for _, video := range []*int{nil, ptr(-1), ptr(30)} {
							for _, after := range []string{"", "2027-01-31"} {
								out = append(out, Robots{
									Index: index, Follow: follow,
									NoArchive: flags&1 != 0, NoSnippet: flags&2 != 0, NoImageIndex: flags&4 != 0,
									MaxSnippet: snippet, MaxImagePreview: image, MaxVideoPreview: video,
									UnavailableAfter: after,
								})
							}
						}
					}
				}
			}
		}
	}
	return out
}

func TestRobotsValueRoundTrip(t *testing.T) {
	rng := rand.New(rand.NewSource(32))
	combos := robotsCombinations()
	if len(combos) != 3*3*8*4*4*3*2 {
		t.Fatalf("%d combinations", len(combos))
	}
	for _, want := range combos {
		value := want.String()
		got, err := ParseRobots(value)
		if err != nil {
			t.Fatalf("ParseRobots(%q): %v", value, err)
		}
		if got.String() != value {
			t.Fatalf("round trip %q -> %q", value, got.String())
		}
		if got.Header() != strings.ReplaceAll(value, ",", ", ") {
			t.Fatalf("Header(%q) = %q", value, got.Header())
		}
		if got.Empty() != (value == "") {
			t.Fatalf("Empty(%q) = %v", value, got.Empty())
		}
		// Any order, spaces and case read the same value back in the
		// fixed order.
		parts := strings.Split(value, ",")
		rng.Shuffle(len(parts), func(i, j int) { parts[i], parts[j] = parts[j], parts[i] })
		for i := range parts {
			if i%2 == 0 {
				parts[i] = " " + strings.ToUpper(parts[i]) + " "
			}
		}
		if value != "" {
			norm, err := NormalizeRobots(strings.Join(parts, ","))
			if err != nil || norm != value {
				t.Fatalf("NormalizeRobots(%q) = %q, %v; want %q", strings.Join(parts, ","), norm, err, value)
			}
		}
	}
}

func TestRobotsValueAllInheritIsEmpty(t *testing.T) {
	for _, value := range []string{"", "   ", "\t"} {
		r, err := ParseRobots(value)
		if err != nil || !r.Empty() || r.String() != "" {
			t.Fatalf("ParseRobots(%q) = %+v, %v", value, r, err)
		}
	}
	if s := (Robots{}).String(); s != "" {
		t.Fatalf("all-inherit serialises to %q", s)
	}
}

func TestRobotsValueMalformed(t *testing.T) {
	for _, value := range []string{
		",", "index,", ",noindex", "index,,follow",
		"index,noindex", "follow,nofollow", "noindex,noindex", "noarchive,noarchive",
		"max-snippet:1,max-snippet:2",
		"index:1", "nofollow:yes", "noarchive:1",
		"max-snippet", "max-snippet:", "max-snippet:abc", "max-snippet:-2", "max-snippet:1.5",
		"max-video-preview", "max-video-preview:-5",
		"max-image-preview", "max-image-preview:huge", "max-image-preview:",
		"unavailable_after", "unavailable_after:2027-13-01", "unavailable_after:2027-02-30",
		"unavailable_after:27-01-01", "unavailable_after:2027-1-1",
		"none", "all", "noodp", "indexx",
	} {
		if _, err := ParseRobots(value); !errors.Is(err, ErrRobotsValue) {
			t.Errorf("ParseRobots(%q) = %v, want ErrRobotsValue", value, err)
		}
		if _, err := NormalizeRobots(value); err == nil {
			t.Errorf("NormalizeRobots(%q) accepted", value)
		}
	}
}

func TestRobotsValueInherit(t *testing.T) {
	parse := func(v string) Robots {
		t.Helper()
		r, err := ParseRobots(v)
		if err != nil {
			t.Fatal(err)
		}
		return r
	}
	for _, tc := range []struct{ upper, lower, want string }{
		{"", "", ""},
		{"noindex", "index,nofollow", "noindex,nofollow"},
		{"", "noindex,follow", "noindex,follow"},
		{"index,follow", "noindex,nofollow,noarchive", "index,follow,noarchive"},
		{"max-snippet:10", "max-snippet:50,max-image-preview:large", "max-snippet:10,max-image-preview:large"},
		{"unavailable_after:2027-01-01", "unavailable_after:2028-01-01,max-video-preview:5", "max-video-preview:5,unavailable_after:2027-01-01"},
		{"nosnippet", "noimageindex", "nosnippet,noimageindex"},
	} {
		if got := parse(tc.upper).Inherit(parse(tc.lower)).String(); got != tc.want {
			t.Errorf("%q over %q = %q, want %q", tc.upper, tc.lower, got, tc.want)
		}
	}
}