package renderdelivery

import (
	"bytes"
	"context"
	"errors"
	"log/slog"
	"os"
	"path/filepath"
	"testing"
	"time"

	templatedir "galaxy/mail/internal/adapters/templates"
	"galaxy/mail/internal/domain/attempt"
	"galaxy/mail/internal/domain/common"
	deliverydomain "galaxy/mail/internal/domain/delivery"

	"github.com/stretchr/testify/require"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
)

func TestServiceExecuteRendersExactLocale(t *testing.T) {
	t.Parallel()

	catalog := newTestCatalog(t, map[string]string{
		filepath.Join("auth.login_code", "en", "subject.tmpl"):    "Your login code",
		filepath.Join("auth.login_code", "en", "text.tmpl"):       "Code: {{.code}}",
		filepath.Join("game.turn_ready", "fr-fr", "subject.tmpl"): "Tour {{.turn_number}}",
		filepath.Join("game.turn_ready", "fr-fr", "text.tmpl"):    "Bonjour {{with .player}}{{.name}}{{end}}",
		filepath.Join("game.turn_ready", "fr-fr", "html.tmpl"):    "<p>{{.player.name}}</p>",
	})

	store := &stubStore{}
	service := newTestService(t, Config{
		Catalog: catalog,
		Store:   store,
		Clock:   stubClock{now: fixedNow()},
	})

	result, err := service.Execute(context.Background(), validInput(t, "fr-FR"))
	require.NoError(t, err)
	require.Equal(t, OutcomeRendered, result.Outcome)
	require.Equal(t, common.Locale("fr-FR"), result.ResolvedLocale)
	require.False(t, result.LocaleFallbackUsed)
	require.NotEmpty(t, result.TemplateVersion)
	require.Nil(t, result.Attempt)
	require.Equal(t, deliverydomain.StatusRendered, result.Delivery.Status)
	require.Equal(t, deliverydomain.Content{
		Subject:  "Tour 54",
		TextBody: "Bonjour Pilot",
		HTMLBody: "<p>Pilot</p>",
	}, result.Delivery.Content)
	require.Len(t, store.renderedInputs, 1)
	require.Empty(t, store.failedInputs)
}

func TestServiceExecuteFallsBackToEnglish(t *testing.T) {
	t.Parallel()

	catalog := newTestCatalog(t, map[string]string{
		filepath.Join("auth.login_code", "en", "subject.tmpl"): "Your login code",
		filepath.Join("auth.login_code", "en", "text.tmpl"):    "Code: {{.code}}",
		filepath.Join("game.turn_ready", "en", "subject.tmpl"): "Turn {{.turn_number}}",
		filepath.Join("game.turn_ready", "en", "text.tmpl"):    "Hello {{.player.name}}",
	})

	store := &stubStore{}
	service := newTestService(t, Config{
		Catalog: catalog,
		Store:   store,
		Clock:   stubClock{now: fixedNow()},
	})

	result, err := service.Execute(context.Background(), validInput(t, "fr-FR"))
	require.NoError(t, err)
	require.Equal(t, OutcomeRendered, result.Outcome)
	require.Equal(t, common.Locale("en"), result.ResolvedLocale)
	require.True(t, result.LocaleFallbackUsed)
	require.True(t, result.Delivery.LocaleFallbackUsed)
}

func TestServiceExecuteRecordsLocaleFallbackAndLogsFields(t *testing.T) {
	t.Parallel()

	catalog := newTestCatalog(t, map[string]string{
		filepath.Join("auth.login_code", "en", "subject.tmpl"): "Your login code",
		filepath.Join("auth.login_code", "en", "text.tmpl"):    "Code: {{.code}}",
		filepath.Join("game.turn_ready", "en", "subject.tmpl"): "Turn {{.turn_number}}",
		filepath.Join("game.turn_ready", "en", "text.tmpl"):    "Hello {{.player.name}}",
	})

	telemetry := &stubTelemetry{}
	loggerBuffer := &bytes.Buffer{}
	recorder := tracetest.NewSpanRecorder()
	tracerProvider := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(recorder))

	service := newTestService(t, Config{
		Catalog:        catalog,
		Store:          &stubStore{},
		Clock:          stubClock{now: fixedNow()},
		Telemetry:      telemetry,
		TracerProvider: tracerProvider,
		Logger:         slog.New(slog.NewJSONHandler(loggerBuffer, nil)),
	})

	_, err := service.Execute(context.Background(), validInput(t, "fr-FR"))
	require.NoError(t, err)
	require.Equal(t, []string{"notification:rendered"}, telemetry.statuses)
	require.Equal(t, []string{"game.turn_ready:fr-FR:en"}, telemetry.fallbacks)
	require.Contains(t, loggerBuffer.String(), "\"delivery_id\":\"delivery-123\"")
	require.Contains(t, loggerBuffer.String(), "\"source\":\"notification\"")
	require.Contains(t, loggerBuffer.String(), "\"template_id\":\"game.turn_ready\"")
	require.Contains(t, loggerBuffer.String(), "\"attempt_no\":1")
	require.Contains(t, loggerBuffer.String(), "\"otel_trace_id\":")
	require.True(t, hasRenderSpanNamed(recorder.Ended(), "mail.render_delivery"))
}

func TestServiceExecuteFailsOnMissingRequiredVariable(t *testing.T) {
	t.Parallel()

	catalog := newTestCatalog(t, map[string]string{
		filepath.Join("auth.login_code", "en", "subject.tmpl"): "Your login code",
		filepath.Join("auth.login_code", "en", "text.tmpl"):    "Code: {{.code}}",
		filepath.Join("game.turn_ready", "en", "subject.tmpl"): "Turn {{.turn_number}}",
		filepath.Join("game.turn_ready", "en", "text.tmpl"):    "Hello {{.player.name}}",
	})

	store := &stubStore{}
	service := newTestService(t, Config{
		Catalog: catalog,
		Store:   store,
		Clock:   stubClock{now: fixedNow()},
	})

	input := validInput(t, "en")
	delete(input.Delivery.TemplateVariables, "player")

	result, err := service.Execute(context.Background(), input)
	require.NoError(t, err)
	require.Equal(t, OutcomeFailed, result.Outcome)
	require.Equal(t, FailureMissingRequiredVariable, result.FailureClassification)
	require.NotNil(t, result.Attempt)
	require.Equal(t, attempt.StatusRenderFailed, result.Attempt.Status)
	require.Equal(t, "missing required variables: player.name", result.Attempt.ProviderSummary)
	require.Len(t, store.failedInputs, 1)
	require.Empty(t, store.renderedInputs)
}

func TestServiceExecuteFailsOnTemplateExecutionError(t *testing.T) {
	t.Parallel()

	catalog := newTestCatalog(t, map[string]string{
		filepath.Join("auth.login_code", "en", "subject.tmpl"): "Your login code",
		filepath.Join("auth.login_code", "en", "text.tmpl"):    "Code: {{.code}}",
		filepath.Join("game.turn_ready", "en", "subject.tmpl"): "{{call .callable}}",
		filepath.Join("game.turn_ready", "en", "text.tmpl"):    "Hello {{.player.name}}",
	})

	store := &stubStore{}
	service := newTestService(t, Config{
		Catalog: catalog,
		Store:   store,
		Clock:   stubClock{now: fixedNow()},
	})

	input := validInput(t, "en")
	input.Delivery.TemplateVariables["callable"] = "not-a-func"

	result, err := service.Execute(context.Background(), input)
	require.NoError(t, err)
	require.Equal(t, OutcomeFailed, result.Outcome)
	require.Equal(t, FailureTemplateExecuteFailed, result.FailureClassification)
	require.Equal(t, "template execution failed", result.Attempt.ProviderSummary)
}

func TestServiceExecuteClassifiesTemplateNotFound(t *testing.T) {
	t.Parallel()

	service := newTestService(t, Config{
		Catalog: stubCatalog{
			lookupErr: templatedir.ErrTemplateNotFound,
		},
		Store: &stubStore{},
		Clock: stubClock{now: fixedNow()},
	})

	result, err := service.Execute(context.Background(), validInput(t, "en"))
	require.NoError(t, err)
	require.Equal(t, OutcomeFailed, result.Outcome)
	require.Equal(t, FailureTemplateNotFound, result.FailureClassification)
}

func TestServiceExecuteClassifiesFallbackMissing(t *testing.T) {
	t.Parallel()

	service := newTestService(t, Config{
		Catalog: stubCatalog{
			lookupErr: templatedir.ErrFallbackMissing,
		},
		Store: &stubStore{},
		Clock: stubClock{now: fixedNow()},
	})

	result, err := service.Execute(context.Background(), validInput(t, "fr-FR"))
	require.NoError(t, err)
	require.Equal(t, OutcomeFailed, result.Outcome)
	require.Equal(t, FailureFallbackMissing, result.FailureClassification)
}

func TestServiceExecuteClassifiesTemplateParseFailure(t *testing.T) {
	t.Parallel()

	service := newTestService(t, Config{
		Catalog: stubCatalog{
			lookupErr: templatedir.ErrTemplateParseFailed,
		},
		Store: &stubStore{},
		Clock: stubClock{now: fixedNow()},
	})

	result, err := service.Execute(context.Background(), validInput(t, "en"))
	require.NoError(t, err)
	require.Equal(t, OutcomeFailed, result.Outcome)
	require.Equal(t, FailureTemplateParseFailed, result.FailureClassification)
}

func TestServiceExecuteReturnsServiceUnavailableOnStoreFailure(t *testing.T) {
	t.Parallel()

	catalog := newTestCatalog(t, map[string]string{
		filepath.Join("auth.login_code", "en", "subject.tmpl"): "Your login code",
		filepath.Join("auth.login_code", "en", "text.tmpl"):    "Code: {{.code}}",
		filepath.Join("game.turn_ready", "en", "subject.tmpl"): "Turn {{.turn_number}}",
		filepath.Join("game.turn_ready", "en", "text.tmpl"):    "Hello {{.player.name}}",
	})

	service := newTestService(t, Config{
		Catalog: catalog,
		Store: &stubStore{
			markRenderedErr: errors.New("redis unavailable"),
		},
		Clock: stubClock{now: fixedNow()},
	})

	_, err := service.Execute(context.Background(), validInput(t, "en"))
	require.Error(t, err)
	require.ErrorIs(t, err, ErrServiceUnavailable)
}

type stubStore struct {
	renderedInputs  []MarkRenderedInput
	failedInputs    []MarkRenderFailedInput
	markRenderedErr error
	markFailedErr   error
}

func (store *stubStore) MarkRendered(_ context.Context, input MarkRenderedInput) error {
	store.renderedInputs = append(store.renderedInputs, input)
	return store.markRenderedErr
}

func (store *stubStore) MarkRenderFailed(_ context.Context, input MarkRenderFailedInput) error {
	store.failedInputs = append(store.failedInputs, input)
	return store.markFailedErr
}

type stubCatalog struct {
	lookupResult templatedir.ResolvedTemplate
	lookupErr    error
}

func (catalog stubCatalog) Lookup(common.TemplateID, common.Locale) (templatedir.ResolvedTemplate, error) {
	return catalog.lookupResult, catalog.lookupErr
}

type stubClock struct {
	now time.Time
}

func (clock stubClock) Now() time.Time {
	return clock.now
}

func newTestService(t *testing.T, cfg Config) *Service {
	t.Helper()

	service, err := New(cfg)
	require.NoError(t, err)

	return service
}

func newTestCatalog(t *testing.T, files map[string]string) *templatedir.Catalog {
	t.Helper()

	rootDir := t.TempDir()
	for path, contents := range files {
		absolutePath := filepath.Join(rootDir, path)
		require.NoError(t, os.MkdirAll(filepath.Dir(absolutePath), 0o755))
		require.NoError(t, os.WriteFile(absolutePath, []byte(contents), 0o644))
	}

	catalog, err := templatedir.NewCatalog(rootDir)
	require.NoError(t, err)

	return catalog
}

type stubTelemetry struct {
	statuses  []string
	attempts  []string
	fallbacks []string
}

func (telemetry *stubTelemetry) RecordDeliveryStatusTransition(_ context.Context, status string, source string) {
	telemetry.statuses = append(telemetry.statuses, source+":"+status)
}

func (telemetry *stubTelemetry) RecordAttemptOutcome(_ context.Context, status string, source string) {
	telemetry.attempts = append(telemetry.attempts, source+":"+status)
}

func (telemetry *stubTelemetry) RecordLocaleFallback(_ context.Context, templateID string, requestedLocale string, resolvedLocale string) {
	telemetry.fallbacks = append(telemetry.fallbacks, templateID+":"+requestedLocale+":"+resolvedLocale)
}

func hasRenderSpanNamed(spans []sdktrace.ReadOnlySpan, name string) bool {
	for _, span := range spans {
		if span.Name() == name {
			return true
		}
	}

	return false
}

func validInput(t *testing.T, localeValue string) Input {
	t.Helper()

	locale, err := common.ParseLocale(localeValue)
	require.NoError(t, err)

	createdAt := fixedNow().Add(-time.Minute)
	deliveryRecord := deliverydomain.Delivery{
		DeliveryID:  common.DeliveryID("delivery-123"),
		Source:      deliverydomain.SourceNotification,
		PayloadMode: deliverydomain.PayloadModeTemplate,
		TemplateID:  common.TemplateID("game.turn_ready"),
		Envelope: deliverydomain.Envelope{
			To: []common.Email{common.Email("pilot@example.com")},
		},
		Locale: locale,
		TemplateVariables: map[string]any{
			"turn_number": float64(54),
			"player": map[string]any{
				"name": "Pilot",
			},
		},
		IdempotencyKey: common.IdempotencyKey("notification:delivery-123"),
		Status:         deliverydomain.StatusQueued,
		AttemptCount:   1,
		CreatedAt:      createdAt,
		UpdatedAt:      createdAt,
	}
	require.NoError(t, deliveryRecord.Validate())

	scheduledFor := createdAt
	attemptRecord := attempt.Attempt{
		DeliveryID:   deliveryRecord.DeliveryID,
		AttemptNo:    1,
		ScheduledFor: scheduledFor,
		Status:       attempt.StatusScheduled,
	}
	require.NoError(t, attemptRecord.Validate())

	return Input{
		Delivery: deliveryRecord,
		Attempt:  attemptRecord,
	}
}

func fixedNow() time.Time {
	return time.Unix(1_775_121_700, 0).UTC()
}