package seeder_test

import (
	"testing"
	"time"

	"github.com/krow/krow-backend/go-api/internal/seeder"
)

func activityFixture() []map[string]any {
	// The authored shape: a burst, then a gap, then a later cluster.
	return []map[string]any{
		{"id": "act_1", "event_type": "create_position", "created_date": "2026-07-18T09:00:00.000Z"},
		{"id": "act_2", "event_type": "apply_job", "created_date": "2026-07-24T09:00:00.000Z"},
		{"id": "act_3", "event_type": "hire_candidate", "created_date": "2026-07-25T09:00:00.000Z"},
		{"id": "act_4", "event_type": "login", "created_date": "2026-08-06T09:00:00.000Z"},
	}
}

func mustTime(t *testing.T, rec map[string]any) time.Time {
	t.Helper()
	at, err := time.Parse(time.RFC3339, rec["created_date"].(string))
	if err != nil {
		t.Fatalf("created_date %v does not parse: %v", rec["created_date"], err)
	}
	return at
}

// The newest event lands on now, so the demo always has something recent.
func TestRebaseActivityAnchorsTheNewestEventToNow(t *testing.T) {
	now := time.Date(2027, 3, 14, 12, 0, 0, 0, time.UTC)
	out := seeder.RebaseToNow(activityFixture(), "created_date", now)

	if len(out) != 4 {
		t.Fatalf("got %d records, want 4", len(out))
	}
	newest := mustTime(t, out[3])
	if !newest.Equal(now) {
		t.Errorf("newest event at %s, want %s", newest, now)
	}
	for _, rec := range out {
		if at := mustTime(t, rec); at.After(now) {
			t.Errorf("%v is in the future at %s", rec["id"], at)
		}
	}
}

// Every gap is preserved. The shape of this data — three hires on one day, a
// quiet fortnight before it — is what every reader of it is looking at.
func TestRebaseActivityPreservesTheGaps(t *testing.T) {
	in := activityFixture()
	now := time.Date(2027, 3, 14, 12, 0, 0, 0, time.UTC)
	out := seeder.RebaseToNow(in, "created_date", now)

	for i := 1; i < len(in); i++ {
		before := mustTime(t, in[i]).Sub(mustTime(t, in[i-1]))
		after := mustTime(t, out[i]).Sub(mustTime(t, out[i-1]))
		if before != after {
			t.Errorf("gap %d changed from %s to %s", i, before, after)
		}
	}
}

// The whole point: events land inside the windows the activity tools ask about.
func TestRebaseActivityLandsInsideTheReportingWindows(t *testing.T) {
	now := time.Date(2027, 3, 14, 12, 0, 0, 0, time.UTC)
	out := seeder.RebaseToNow(activityFixture(), "created_date", now)

	var last7, last30 int
	for _, rec := range out {
		age := now.Sub(mustTime(t, rec))
		if age < 7*24*time.Hour {
			last7++
		}
		if age < 30*24*time.Hour {
			last30++
		}
	}
	if last7 == 0 {
		t.Error("no events in the last 7 days — the demo still looks dead, " +
			"which is the condition this function exists to prevent")
	}
	if last30 != 4 {
		t.Errorf("%d of 4 events in the last 30 days, want all of them", last30)
	}
}

// Seeding twice must not compound the shift.
func TestRebaseActivityIsIdempotent(t *testing.T) {
	now := time.Date(2027, 3, 14, 12, 0, 0, 0, time.UTC)
	first := seeder.RebaseToNow(activityFixture(), "created_date", now)
	second := seeder.RebaseToNow(activityFixture(), "created_date", now)

	for i := range first {
		if first[i]["created_date"] != second[i]["created_date"] {
			t.Errorf("record %d differs between runs: %v vs %v",
				i, first[i]["created_date"], second[i]["created_date"])
		}
	}
}

// The fixture is read once and may be seeded into several organizations, so
// rebasing must not rewrite it in place.
func TestRebaseActivityDoesNotMutateTheFixture(t *testing.T) {
	in := activityFixture()
	original := in[0]["created_date"]
	seeder.RebaseToNow(in, "created_date", time.Date(2027, 3, 14, 12, 0, 0, 0, time.UTC))
	if in[0]["created_date"] != original {
		t.Errorf("the fixture was rewritten in place: %v became %v",
			original, in[0]["created_date"])
	}
}

func TestRebaseActivityHandlesNothingToDo(t *testing.T) {
	now := time.Now()
	if got := seeder.RebaseToNow(nil, "created_date", now); got != nil {
		t.Errorf("nil in, %v out", got)
	}
	if got := seeder.RebaseToNow([]map[string]any{}, "created_date", now); len(got) != 0 {
		t.Errorf("empty in, %d out", len(got))
	}
	// Unparseable dates are left alone rather than guessed at.
	junk := []map[string]any{{"id": "x", "created_date": "not a date"}}
	out := seeder.RebaseToNow(junk, "created_date", now)
	if out[0]["created_date"] != "not a date" {
		t.Errorf("an unreadable date was rewritten to %v", out[0]["created_date"])
	}
}

// The gap WITHIN a record matters as much as the gaps between records.
// buildHires subtracts an application's created_date from its updated_date to
// get time-to-hire, so shifting one and not the other invents a hire that took
// three weeks or minus one. The seeder's TestSeedPreservesSourceValues caught
// this the first time; this pins it where the shifting happens.
func TestRebaseToNowShiftsEveryTimestampTogether(t *testing.T) {
	in := []map[string]any{
		{
			"id":           "app_1",
			"created_date": "2026-07-20T09:00:00.000Z",
			"updated_date": "2026-07-25T09:00:00.000Z", // five days later
			"status":       "hired",
			"ai_score":     91,
		},
		{
			"id":           "app_2",
			"created_date": "2026-08-06T09:00:00.000Z",
			"updated_date": "2026-08-06T09:00:00.000Z",
			"status":       "applied",
		},
	}
	now := time.Date(2027, 3, 14, 12, 0, 0, 0, time.UTC)
	out := seeder.RebaseToNow(in, "created_date", now)

	created := mustTime(t, out[0])
	updated, err := time.Parse(time.RFC3339, out[0]["updated_date"].(string))
	if err != nil {
		t.Fatalf("updated_date did not survive as a timestamp: %v", out[0]["updated_date"])
	}
	if gap := updated.Sub(created); gap != 5*24*time.Hour {
		t.Errorf("time-to-hire became %s, want 120h — the two timestamps moved "+
			"by different amounts", gap)
	}

	// Non-date fields are untouched.
	if out[0]["status"] != "hired" || out[0]["ai_score"] != 91 {
		t.Errorf("a non-date field was rewritten: %+v", out[0])
	}
	// And a record whose two dates were equal still has them equal.
	if out[1]["created_date"] != out[1]["updated_date"] {
		t.Errorf("equal timestamps diverged: %v vs %v",
			out[1]["created_date"], out[1]["updated_date"])
	}
}