package backup

import (
	"bytes"
	"context"
	"errors"
	"io"
	"strings"
	"testing"
	"time"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

func at(s string) time.Time {
	t, err := time.Parse(time.RFC3339, s)
	if err != nil {
		panic(err)
	}
	return t
}

func TestDueRunsAtTheHourCatchesUpAndBacksOffAfterAFailure(t *testing.T) {
	cases := []struct {
		name string
		now  string
		t    runTimes
		want string
	}{
		{"never run: the slot that passed is due", "2026-11-02T10:00:00Z",
			runTimes{}, "2026-11-02T03:00:00Z"},
		{"ran at the hour: tomorrow's slot", "2026-11-02T10:00:00Z",
			runTimes{lastSuccess: at("2026-11-02T03:00:05Z"), lastAttempt: at("2026-11-02T03:00:05Z")}, "2026-11-03T03:00:00Z"},
		{"before today's hour, yesterday's ran: today's slot", "2026-11-02T02:00:00Z",
			runTimes{lastSuccess: at("2026-11-01T03:00:05Z"), lastAttempt: at("2026-11-01T03:00:05Z")}, "2026-11-02T03:00:00Z"},
		{"server was down at the hour: catches up", "2026-11-02T10:00:00Z",
			runTimes{lastSuccess: at("2026-11-01T03:00:05Z"), lastAttempt: at("2026-11-01T03:00:05Z")}, "2026-11-02T03:00:00Z"},
		{"first failure: an hour later", "2026-11-02T03:30:00Z",
			runTimes{lastAttempt: at("2026-11-02T03:00:00Z"), failingSince: at("2026-11-02T03:00:00Z")}, "2026-11-02T04:00:00Z"},
		{"failing for two hours: two hours later", "2026-11-02T05:30:00Z",
			runTimes{lastAttempt: at("2026-11-02T05:00:00Z"), failingSince: at("2026-11-02T03:00:00Z")}, "2026-11-02T07:00:00Z"},
		{"a retry past the next slot waits for the slot", "2026-11-02T19:30:00Z",
			runTimes{lastAttempt: at("2026-11-02T19:00:00Z"), failingSince: at("2026-11-02T03:00:00Z")}, "2026-11-03T03:00:00Z"},
	}
	for _, c := range cases {
		if got := due(at(c.now), 3, c.t); !got.Equal(at(c.want)) {
			t.Errorf("%s: due = %s, want %s", c.name, got.Format(time.RFC3339), c.want)
		}
	}
}

func TestTheHourIsUTC(t *testing.T) {
	// 22:00 at UTC-5 is 03:00 UTC the next day, which is that day's slot.
	now := time.Date(2026, 11, 1, 22, 0, 0, 0, time.FixedZone("x", -5*3600))
	if got := slotBefore(now, 3); !got.Equal(at("2026-11-02T03:00:00Z")) {
		t.Errorf("slot = %s", got)
	}
}

func TestVerdict(t *testing.T) {
	now := at("2026-11-02T10:00:00Z")
	on := dbq.BackupSetting{Enabled: true}
	good := runTimes{lastSuccess: at("2026-11-02T03:00:00Z"), lastAttempt: at("2026-11-02T03:00:00Z")}
	cases := []struct {
		name  string
		st    dbq.BackupSetting
		probs []string
		t     runTimes
		want  string
	}{
		{"switched off, even with problems and failures", dbq.BackupSetting{}, []string{"x"}, runTimes{failingSince: now}, StateOff},
		{"on but not set up", on, []string{"x"}, good, StateIncomplete},
		{"the latest run failed", on, nil, runTimes{lastSuccess: good.lastSuccess, failingSince: now}, StateFailing},
		{"nothing has run yet", on, nil, runTimes{}, StateWaiting},
		{"the latest backup is old", on, nil, runTimes{lastSuccess: now.Add(-27 * time.Hour)}, StateOverdue},
		{"a day and a bit is still fine", on, nil, runTimes{lastSuccess: now.Add(-25 * time.Hour)}, StateOK},
		{"fine", on, nil, good, StateOK},
	}
	for _, c := range cases {
		if got := verdict(c.st, c.probs, c.t, now); got != c.want {
			t.Errorf("%s: %s, want %s", c.name, got, c.want)
		}
	}
}

func TestProblemsNameWhatIsMissing(t *testing.T) {
	if p := problems(dbq.BackupSetting{Destination: DestinationS3}); len(p) != 4 {
		t.Errorf("an empty bucket: %v, want endpoint, name, access key and secret key", p)
	}
	if p := problems(dbq.BackupSetting{Destination: DestinationS3, Endpoint: "https://s3.example.com", Bucket: "b", AccessKey: "a", SecretKey: "v1.x"}); len(p) != 0 {
		t.Errorf("a whole bucket: %v", p)
	}
	if p := problems(dbq.BackupSetting{Destination: DestinationFolder}); len(p) != 1 {
		t.Errorf("an empty folder: %v", p)
	}
	if p := problems(dbq.BackupSetting{Destination: DestinationFolder, Folder: "/backups"}); len(p) != 0 {
		t.Errorf("a folder: %v", p)
	}
}

func TestMergeRefusesWhatCannotBeKept(t *testing.T) {
	ok := Update{Destination: DestinationS3, RunHour: 3}
	for field, u := range map[string]func(Update) Update{
		"destination":      func(u Update) Update { u.Destination = "ftp"; return u },
		"run_hour":         func(u Update) Update { u.RunHour = 24; return u },
		"upload_limit_kib": func(u Update) Update { u.UploadLimitKiB = -1; return u },
		"folder":           func(u Update) Update { u.Folder = "backups"; return u },
		"endpoint":         func(u Update) Update { u.Endpoint = "s3.example.com"; return u },
	} {
		_, err := merge(dbq.BackupSetting{}, u(ok))
		var fe *FieldError
		if !errors.As(err, &fe) || fe.Field != field {
			t.Errorf("%s: err = %v, want a FieldError on it", field, err)
		}
	}
}

func TestMergeTidiesAndKeepsTheStoredSecret(t *testing.T) {
	st, err := merge(dbq.BackupSetting{SecretKey: "v1.stored"}, Update{
		Enabled: true, Destination: DestinationS3, Endpoint: " https://s3.example.com/ ",
		Bucket: " minstrel ", AccessKey: " ak ", RunHour: 4, UploadLimitKiB: 512, Folder: "/srv/backups/",
	})
	if err != nil {
		t.Fatal(err)
	}
	if st.Endpoint != "https://s3.example.com" || st.Bucket != "minstrel" || st.AccessKey != "ak" ||
		st.SecretKey != "v1.stored" || st.RunHour != 4 || st.UploadLimitKib != 512 || st.Folder != "/srv/backups" || !st.Enabled {
		t.Errorf("merged = %+v", st)
	}
}

func TestThrottleKeepsToItsRate(t *testing.T) {
	data := bytes.Repeat([]byte("x"), 20*1024)
	start := time.Now()
	got, err := io.ReadAll(Throttle(context.Background(), bytes.NewReader(data), 100*1024))
	if err != nil || !bytes.Equal(got, data) {
		t.Fatalf("read %d bytes, err %v", len(got), err)
	}
	// 20 KiB at 100 KiB a second takes at least a fifth of a second.
	if took := time.Since(start); took < 180*time.Millisecond {
		t.Errorf("took %s, want at least 200ms", took)
	}
}

func TestThrottleWithNoLimitIsTheReaderItself(t *testing.T) {
	r := strings.NewReader("x")
	if Throttle(context.Background(), r, 0) != io.Reader(r) {
		t.Error("a zero limit wrapped the reader")
	}
}

func TestThrottleStopsWhenItsContextEnds(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	_, err := io.ReadAll(Throttle(ctx, bytes.NewReader(make([]byte, 4096)), 1024))
	if !errors.Is(err, context.Canceled) {
		t.Errorf("err = %v, want context.Canceled", err)
	}
}

func TestDescribeSaysWhyARunStopped(t *testing.T) {
	if got := describe(context.DeadlineExceeded); !strings.Contains(got, "longer than 30 minutes") {
		t.Errorf("deadline: %q", got)
	}
	if got := describe(context.Canceled); !strings.Contains(got, "server stopped") {
		t.Errorf("canceled: %q", got)
	}
	if got := describe(errors.New("backup: the folder /x isn't there")); got != "the folder /x isn't there" {
		t.Errorf("other: %q", got)
	}
}