package history

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"strings"
	"time"
)

type AdminCancelSourceFilter struct {
	SourceTypes       []string   `json:"source_types"`
	DateFrom          *time.Time `json:"date_from,omitempty"`
	DateTo            *time.Time `json:"date_to,omitempty"`
	SourceRefEquals   *string    `json:"source_ref_equals,omitempty"`
	SourceRefContains *string    `json:"source_ref_contains,omitempty"`
	AllowExistingJobs bool       `json:"allow_existing_jobs,omitempty"`
	SkipRecompute     bool       `json:"skip_recompute,omitempty"`
	Reason            *string    `json:"reason,omitempty"`
	MaxEvents         int        `json:"max_events,omitempty"`
	RequestedBy       *string    `json:"requested_by,omitempty"`
}

type AdminCancelPreview struct {
	MatchedEvents        int                       `json:"matched_events"`
	ComponentEvents      int                       `json:"component_events"`
	AssetEvents          int                       `json:"asset_events"`
	AffectedEntities     int                       `json:"affected_entities"`
	AffectedComponents   int                       `json:"affected_components"`
	AffectedAssets       int                       `json:"affected_assets"`
	BySource             map[string]int            `json:"by_source"`
	EntityCountsBySource map[string]map[string]int `json:"entity_counts_by_source"`
	Sample               []AdminCancelPreviewEvent `json:"sample"`
	Truncated            bool                      `json:"truncated"`
	MaxEvents            int                       `json:"max_events"`
}

type AdminCancelPreviewEvent struct {
	EntityType    string    `json:"entity_type"`
	EntityID      string    `json:"entity_id"`
	EventID       string    `json:"event_id"`
	SourceType    string    `json:"source_type"`
	SourceRef     *string   `json:"source_ref,omitempty"`
	ChangeType    string    `json:"change_type"`
	EffectiveAt   time.Time `json:"effective_at"`
	CorrelationID *string   `json:"correlation_id,omitempty"`
}

type AdminCancelExecuteResult struct {
	Preview             AdminCancelPreview `json:"preview"`
	SoftDeletedEvents   int                `json:"soft_deleted_events"`
	QueuedJobs          []JobRecord        `json:"queued_jobs"`
	QueuedJobsCount     int                `json:"queued_jobs_count"`
	SkippedJobConflicts int                `json:"skipped_job_conflicts,omitempty"`
}

type adminCancelMatch struct {
	EntityType    string
	EntityID      string
	EventID       string
	SourceType    string
	SourceRef     *string
	ChangeType    string
	EffectiveAt   time.Time
	CorrelationID *string
}

const adminCancelMaxEventsLimit = 100000

func (s *Service) PreviewCancelEventsBySource(ctx context.Context, filter AdminCancelSourceFilter) (AdminCancelPreview, error) {
	if s == nil || s.db == nil {
		return AdminCancelPreview{}, fmt.Errorf("history service unavailable")
	}
	filter = normalizeAdminCancelFilter(filter)
	matches, err := s.findAdminCancelMatches(ctx, nil, filter)
	if err != nil {
		return AdminCancelPreview{}, err
	}
	return s.buildAdminCancelPreview(ctx, nil, matches, filter.MaxEvents), nil
}

func (s *Service) QueueCancelEventsBySource(ctx context.Context, filter AdminCancelSourceFilter) (AdminCancelExecuteResult, error) {
	if s == nil || s.db == nil {
		return AdminCancelExecuteResult{}, fmt.Errorf("history service unavailable")
	}
	filter = normalizeAdminCancelFilter(filter)
	tx, err := s.db.BeginTx(ctx, &sql.TxOptions{})
	if err != nil {
		return AdminCancelExecuteResult{}, err
	}
	defer func() { _ = tx.Rollback() }()

	matches, err := s.findAdminCancelMatches(ctx, tx, filter)
	if err != nil {
		return AdminCancelExecuteResult{}, err
	}
	preview := s.buildAdminCancelPreview(ctx, tx, matches, filter.MaxEvents)
	if len(matches) > filter.MaxEvents {
		return AdminCancelExecuteResult{}, fmt.Errorf("%w: preview truncated, narrow filters or increase max_events", ErrConflict)
	}
	if len(matches) == 0 {
		if err := tx.Commit(); err != nil {
			return AdminCancelExecuteResult{}, err
		}
		return AdminCancelExecuteResult{Preview: preview}, nil
	}

	affectedEntities, err := s.collectAffectedEntitiesForAdminCancel(ctx, tx, matches)
	if err != nil {
		return AdminCancelExecuteResult{}, err
	}
	for key := range affectedEntities {
		entityType, entityID := splitEntityKey(key)
		if err := s.ensureNoRunningJob(ctx, tx, entityType, entityID); err != nil {
			if filter.AllowExistingJobs && err == ErrConflict {
				continue
			}
			return AdminCancelExecuteResult{}, err
		}
	}

	softDeleted, err := s.batchSoftDeleteEvents(ctx, tx, matches, filter.Reason, filter.RequestedBy)
	if err != nil {
		return AdminCancelExecuteResult{}, err
	}

	if filter.SkipRecompute || len(affectedEntities) == 0 {
		if err := tx.Commit(); err != nil {
			return AdminCancelExecuteResult{}, err
		}
		return AdminCancelExecuteResult{
			Preview:           preview,
			SoftDeletedEvents: softDeleted,
		}, nil
	}

	entityKeys := make([]string, 0, len(affectedEntities))
	for key := range affectedEntities {
		entityKeys = append(entityKeys, key)
	}
	batchPayload := map[string]any{
		"entity_keys":  entityKeys,
		"source_types": filter.SourceTypes,
	}
	batchJob, err := s.insertJobTx(ctx, tx, "recompute_batch", "batch", "recompute", batchPayload, filter.RequestedBy)
	if err != nil {
		return AdminCancelExecuteResult{}, err
	}
	if err := tx.Commit(); err != nil {
		return AdminCancelExecuteResult{}, err
	}
	return AdminCancelExecuteResult{
		Preview:           preview,
		SoftDeletedEvents: softDeleted,
		QueuedJobs:        []JobRecord{batchJob},
		QueuedJobsCount:   1,
	}, nil
}

func normalizeAdminCancelFilter(filter AdminCancelSourceFilter) AdminCancelSourceFilter {
	cleaned := make([]string, 0, len(filter.SourceTypes))
	seen := map[string]struct{}{}
	for _, raw := range filter.SourceTypes {
		v := strings.TrimSpace(strings.ToLower(raw))
		if v == "" {
			continue
		}
		if _, ok := seen[v]; ok {
			continue
		}
		seen[v] = struct{}{}
		cleaned = append(cleaned, v)
	}
	filter.SourceTypes = cleaned
	if filter.MaxEvents <= 0 {
		filter.MaxEvents = 1000
	} else if filter.MaxEvents > adminCancelMaxEventsLimit {
		filter.MaxEvents = adminCancelMaxEventsLimit
	}
	filter.SourceRefEquals = normalizeStringPtr(filter.SourceRefEquals)
	filter.SourceRefContains = normalizeStringPtr(filter.SourceRefContains)
	filter.Reason = normalizeStringPtr(filter.Reason)
	filter.RequestedBy = normalizeStringPtr(filter.RequestedBy)
	return filter
}

func (s *Service) findAdminCancelMatches(ctx context.Context, tx *sql.Tx, filter AdminCancelSourceFilter) ([]adminCancelMatch, error) {
	if len(filter.SourceTypes) == 0 {
		return nil, fmt.Errorf("%w: source_types required", ErrInvalidPatch)
	}
	sourceClause, sourceArgs := inClauseStrings(filter.SourceTypes)
	if sourceClause == "" {
		return nil, fmt.Errorf("%w: source_types required", ErrInvalidPatch)
	}

	var args []any
	query := `
		SELECT entity_type, entity_id, event_id, source_type, source_ref, change_type, effective_at, correlation_id
		FROM (
			SELECT 'component' AS entity_type, c.part_id AS entity_id, c.id AS event_id, c.source_type, c.source_ref, c.change_type, c.effective_at, c.correlation_id
			FROM component_change_events c
			WHERE c.is_deleted = FALSE AND c.source_type IN (` + sourceClause + `)
			UNION ALL
			SELECT 'asset' AS entity_type, a.machine_id AS entity_id, a.id AS event_id, a.source_type, a.source_ref, a.change_type, a.effective_at, a.correlation_id
			FROM asset_change_events a
			WHERE a.is_deleted = FALSE AND a.source_type IN (` + sourceClause + `)
		) x
		WHERE 1=1`
	args = append(args, sourceArgs...)
	args = append(args, sourceArgs...)
	if filter.DateFrom != nil {
		query += ` AND x.effective_at >= ?`
		args = append(args, filter.DateFrom.UTC())
	}
	if filter.DateTo != nil {
		query += ` AND x.effective_at <= ?`
		args = append(args, filter.DateTo.UTC())
	}
	if filter.SourceRefEquals != nil {
		query += ` AND x.source_ref = ?`
		args = append(args, *filter.SourceRefEquals)
	}
	if filter.SourceRefContains != nil {
		query += ` AND x.source_ref LIKE ?`
		args = append(args, "%"+*filter.SourceRefContains+"%")
	}
	query += ` ORDER BY x.effective_at, x.entity_type, x.entity_id, x.event_id LIMIT ?`
	args = append(args, filter.MaxEvents+1)

	var (
		rows *sql.Rows
		err  error
	)
	if tx != nil {
		rows, err = tx.QueryContext(ctx, query, args...)
	} else {
		rows, err = s.db.QueryContext(ctx, query, args...)
	}
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	out := make([]adminCancelMatch, 0, minInt(filter.MaxEvents, 256))
	for rows.Next() {
		var m adminCancelMatch
		var sourceRef sql.NullString
		var correlation sql.NullString
		if err := rows.Scan(&m.EntityType, &m.EntityID, &m.EventID, &m.SourceType, &sourceRef, &m.ChangeType, &m.EffectiveAt, &correlation); err != nil {
			return nil, err
		}
		m.SourceRef = nullStringPtr(sourceRef)
		m.CorrelationID = nullStringPtr(correlation)
		out = append(out, m)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return out, nil
}

func (s *Service) buildAdminCancelPreview(ctx context.Context, tx *sql.Tx, matches []adminCancelMatch, maxEvents int) AdminCancelPreview {
	preview := AdminCancelPreview{
		BySource:             map[string]int{},
		EntityCountsBySource: map[string]map[string]int{},
		MaxEvents:            maxEvents,
	}
	entitySet := map[string]struct{}{}
	componentSet := map[string]struct{}{}
	assetSet := map[string]struct{}{}
	for i, m := range matches {
		if i >= maxEvents {
			preview.Truncated = true
			break
		}
		preview.MatchedEvents++
		if m.EntityType == "component" {
			preview.ComponentEvents++
			componentSet[m.EntityID] = struct{}{}
		} else {
			preview.AssetEvents++
			assetSet[m.EntityID] = struct{}{}
		}
		entitySet[entityKey(m.EntityType, m.EntityID)] = struct{}{}
		preview.BySource[m.SourceType]++
		if preview.EntityCountsBySource[m.SourceType] == nil {
			preview.EntityCountsBySource[m.SourceType] = map[string]int{}
		}
		preview.EntityCountsBySource[m.SourceType][m.EntityType]++
		if len(preview.Sample) < 25 {
			preview.Sample = append(preview.Sample, AdminCancelPreviewEvent{
				EntityType:    m.EntityType,
				EntityID:      m.EntityID,
				EventID:       m.EventID,
				SourceType:    m.SourceType,
				SourceRef:     m.SourceRef,
				ChangeType:    m.ChangeType,
				EffectiveAt:   m.EffectiveAt,
				CorrelationID: m.CorrelationID,
			})
		}
	}
	preview.AffectedEntities = len(entitySet)
	preview.AffectedComponents = len(componentSet)
	preview.AffectedAssets = len(assetSet)
	if tx != nil {
		if expanded, err := s.collectAffectedEntitiesForAdminCancel(ctx, tx, matches); err == nil {
			preview.AffectedEntities = len(expanded)
			preview.AffectedComponents = 0
			preview.AffectedAssets = 0
			for key := range expanded {
				if strings.HasPrefix(key, "component:") {
					preview.AffectedComponents++
				}
				if strings.HasPrefix(key, "asset:") {
					preview.AffectedAssets++
				}
			}
		}
	}
	return preview
}

func (s *Service) collectAffectedEntitiesForAdminCancel(ctx context.Context, tx *sql.Tx, matches []adminCancelMatch) (map[string]struct{}, error) {
	out := map[string]struct{}{}
	for _, m := range matches {
		out[entityKey(m.EntityType, m.EntityID)] = struct{}{}
		if m.EntityType != "asset" || m.CorrelationID == nil || strings.TrimSpace(*m.CorrelationID) == "" {
			continue
		}
		rows, err := tx.QueryContext(ctx, `SELECT DISTINCT part_id FROM component_change_events WHERE correlation_id = ?`, *m.CorrelationID)
		if err != nil {
			return nil, err
		}
		for rows.Next() {
			var partID string
			if err := rows.Scan(&partID); err != nil {
				rows.Close()
				return nil, err
			}
			out[entityKey("component", partID)] = struct{}{}
		}
		if err := rows.Err(); err != nil {
			rows.Close()
			return nil, err
		}
		rows.Close()
	}
	return out, nil
}

func entityKey(entityType, entityID string) string {
	return entityType + ":" + entityID
}

func splitEntityKey(key string) (string, string) {
	parts := strings.SplitN(key, ":", 2)
	if len(parts) != 2 {
		return "", key
	}
	return parts[0], parts[1]
}

func inClauseStrings(values []string) (string, []any) {
	if len(values) == 0 {
		return "", nil
	}
	ph := make([]string, 0, len(values))
	args := make([]any, 0, len(values))
	for _, v := range values {
		ph = append(ph, "?")
		args = append(args, v)
	}
	return strings.Join(ph, ","), args
}

func minInt(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func (s *Service) queueGenericRecomputeTx(ctx context.Context, tx *sql.Tx, entityType, entityID string, payload map[string]any, requestedBy *string) (JobRecord, error) {
	return s.insertJobTx(ctx, tx, "recompute", entityType, entityID, payload, requestedBy)
}

func (s *Service) MarshalAdminCancelPreview(preview AdminCancelPreview) ([]byte, error) {
	return json.Marshal(preview)
}

const batchSoftDeleteChunkSize = 500

// batchSoftDeleteEvents soft-deletes all matched events using bulk IN-clause updates
// instead of per-event queries. Returns number of event IDs processed.
func (s *Service) batchSoftDeleteEvents(ctx context.Context, tx *sql.Tx, matches []adminCancelMatch, reason, requestedBy *string) (int, error) {
	if len(matches) == 0 {
		return 0, nil
	}
	now := time.Now().UTC()

	type eventGroup struct {
		ids          []string
		correlations []string // non-empty correlation IDs for asset events
	}
	comp := eventGroup{}
	asset := eventGroup{}
	for _, m := range matches {
		if m.EntityType == "component" {
			comp.ids = append(comp.ids, m.EventID)
		} else {
			asset.ids = append(asset.ids, m.EventID)
			if m.CorrelationID != nil && strings.TrimSpace(*m.CorrelationID) != "" {
				asset.correlations = append(asset.correlations, *m.CorrelationID)
			}
		}
	}

	// Bulk soft-delete component change events
	if err := batchUpdateIsDeleted(ctx, tx,
		"UPDATE component_change_events SET is_deleted = TRUE, deleted_at = ?, deleted_by = ?, deleted_reason = ? WHERE id IN (%s) AND is_deleted = FALSE",
		comp.ids, now, requestedBy, reason,
	); err != nil {
		return 0, err
	}

	// Bulk soft-delete asset change events
	if err := batchUpdateIsDeleted(ctx, tx,
		"UPDATE asset_change_events SET is_deleted = TRUE, deleted_at = ?, deleted_by = ?, deleted_reason = ? WHERE id IN (%s) AND is_deleted = FALSE",
		asset.ids, now, requestedBy, reason,
	); err != nil {
		return 0, err
	}

	// Bulk soft-delete timeline events for all matched event IDs
	allEventIDs := make([]string, 0, len(comp.ids)+len(asset.ids))
	allEventIDs = append(allEventIDs, comp.ids...)
	allEventIDs = append(allEventIDs, asset.ids...)
	if err := batchExecChunked(ctx, tx,
		"UPDATE timeline_events SET is_deleted = TRUE WHERE logical_event_id IN (%s)",
		allEventIDs,
	); err != nil {
		return 0, err
	}

	// For asset events: also soft-delete correlated component events (cascade)
	if len(asset.correlations) > 0 {
		if err := batchUpdateIsDeleted(ctx, tx,
			"UPDATE component_change_events SET is_deleted = TRUE, deleted_at = ?, deleted_by = ?, deleted_reason = COALESCE(?, deleted_reason) WHERE correlation_id IN (%s) AND is_deleted = FALSE",
			asset.correlations, now, requestedBy, reason,
		); err != nil {
			return 0, err
		}
		if err := batchExecChunked(ctx, tx,
			"UPDATE timeline_events SET is_deleted = TRUE WHERE logical_entity_type = 'component' AND logical_event_id IN (SELECT id FROM component_change_events WHERE correlation_id IN (%s))",
			asset.correlations,
		); err != nil {
			return 0, err
		}
	}

	return len(matches), nil
}

// batchUpdateIsDeleted runs UPDATE ... WHERE id IN (...) in chunks.
// The query template must have exactly one %s placeholder for the IN clause
// and must start with 3 fixed args: now, requestedBy, reason.
func batchUpdateIsDeleted(ctx context.Context, tx *sql.Tx, queryTpl string, ids []string, fixedArgs ...any) error {
	for i := 0; i < len(ids); i += batchSoftDeleteChunkSize {
		end := i + batchSoftDeleteChunkSize
		if end > len(ids) {
			end = len(ids)
		}
		chunk := ids[i:end]
		ph, chunkArgs := inClauseStrings(chunk)
		args := make([]any, 0, len(fixedArgs)+len(chunkArgs))
		args = append(args, fixedArgs...)
		args = append(args, chunkArgs...)
		if _, err := tx.ExecContext(ctx, fmt.Sprintf(queryTpl, ph), args...); err != nil {
			return err
		}
	}
	return nil
}

// batchExecChunked runs a query with a single IN clause placeholder in chunks.
func batchExecChunked(ctx context.Context, tx *sql.Tx, queryTpl string, ids []string) error {
	for i := 0; i < len(ids); i += batchSoftDeleteChunkSize {
		end := i + batchSoftDeleteChunkSize
		if end > len(ids) {
			end = len(ids)
		}
		chunk := ids[i:end]
		ph, args := inClauseStrings(chunk)
		if _, err := tx.ExecContext(ctx, fmt.Sprintf(queryTpl, ph), args...); err != nil {
			return err
		}
	}
	return nil
}