package postgres

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

	"github.com/lib/pq"

	"switchboard-core/models"
	"switchboard-core/store"
)

type ChannelStore struct{}

func NewChannelStore() *ChannelStore { return &ChannelStore{} }

func (s *ChannelStore) Create(ctx context.Context, ch *models.Channel) error {
	return DB.QueryRowContext(ctx, `
		INSERT INTO channels (user_id, title, description, type, model, system_prompt,
			provider_config_id, is_archived, is_pinned, folder_id, team_id, settings)
		VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12)
		RETURNING id, created_at, updated_at`,
		ch.UserID, ch.Title, ch.Description, ch.Type, ch.Model, ch.SystemPrompt,
		models.NullString(ch.ProviderConfigID), ch.IsArchived, ch.IsPinned,
		models.NullString(ch.FolderID), models.NullString(ch.TeamID), ToJSON(ch.Settings),
	).Scan(&ch.ID, &ch.CreatedAt, &ch.UpdatedAt)
}

func (s *ChannelStore) GetByID(ctx context.Context, id string) (*models.Channel, error) {
	var ch models.Channel
	var providerConfigID, folderID, teamID sql.NullString
	var desc sql.NullString
	var settingsJSON []byte
	err := DB.QueryRowContext(ctx, `
		SELECT id, user_id, title, description, type, model, system_prompt,
			provider_config_id, is_archived, is_pinned, folder_id, team_id, settings,
			created_at, updated_at
		FROM channels WHERE id = $1`, id).Scan(
		&ch.ID, &ch.UserID, &ch.Title, &desc, &ch.Type, &ch.Model, &ch.SystemPrompt,
		&providerConfigID, &ch.IsArchived, &ch.IsPinned, &folderID, &teamID, &settingsJSON,
		&ch.CreatedAt, &ch.UpdatedAt,
	)
	if err != nil {
		return nil, err
	}
	ch.Description = NullableString(desc)
	ch.ProviderConfigID = NullableStringPtr(providerConfigID)
	ch.FolderID = NullableStringPtr(folderID)
	ch.TeamID = NullableStringPtr(teamID)
	json.Unmarshal(settingsJSON, &ch.Settings)
	return &ch, nil
}

func (s *ChannelStore) Update(ctx context.Context, id string, fields map[string]interface{}) error {
	b := NewUpdate("channels")
	for k, v := range fields {
		if k == "settings" || k == "tags" {
			b.SetJSON(k, v)
		} else {
			b.Set(k, v)
		}
	}
	if !b.HasSets() {
		return nil
	}
	b.Where("id", id)
	_, err := b.Exec(DB)
	return err
}

func (s *ChannelStore) Delete(ctx context.Context, id string) error {
	_, err := DB.ExecContext(ctx, "DELETE FROM channels WHERE id = $1", id)
	return err
}

func (s *ChannelStore) ListForUser(ctx context.Context, userID string, opts store.ListOptions) ([]models.Channel, int, error) {
	// Count
	var total int
	DB.QueryRowContext(ctx, "SELECT COUNT(*) FROM channels WHERE user_id = $1", userID).Scan(&total)

	b := NewSelect(
		"id, user_id, title, description, type, model, system_prompt, provider_config_id, is_archived, is_pinned, folder_id, team_id, settings, created_at, updated_at",
		"channels",
	).Where("user_id = ?", userID)

	if opts.Sort == "" {
		b.OrderBy("updated_at", "DESC")
	}
	b.Paginate(opts)

	q, args := b.Build()
	rows, err := DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	var result []models.Channel
	for rows.Next() {
		var ch models.Channel
		var providerConfigID, folderID, teamID, desc sql.NullString
		var settingsJSON []byte
		err := rows.Scan(&ch.ID, &ch.UserID, &ch.Title, &desc, &ch.Type, &ch.Model,
			&ch.SystemPrompt, &providerConfigID, &ch.IsArchived, &ch.IsPinned,
			&folderID, &teamID, &settingsJSON, &ch.CreatedAt, &ch.UpdatedAt)
		if err != nil {
			return nil, 0, err
		}
		ch.Description = NullableString(desc)
		ch.ProviderConfigID = NullableStringPtr(providerConfigID)
		ch.FolderID = NullableStringPtr(folderID)
		ch.TeamID = NullableStringPtr(teamID)
		json.Unmarshal(settingsJSON, &ch.Settings)
		result = append(result, ch)
	}
	return result, total, rows.Err()
}

func (s *ChannelStore) Search(ctx context.Context, userID, query string, opts store.ListOptions) ([]models.Channel, int, error) {
	// Simple title search for now — will add full-text when search feature lands
	b := NewSelect(
		"id, user_id, title, description, type, model, system_prompt, provider_config_id, is_archived, is_pinned, folder_id, team_id, settings, created_at, updated_at",
		"channels",
	).Where("user_id = ?", userID).Where("title ILIKE ?", "%"+query+"%")
	b.OrderBy("updated_at", "DESC")
	b.Paginate(opts)

	var total int
	DB.QueryRowContext(ctx,
		"SELECT COUNT(*) FROM channels WHERE user_id = $1 AND title ILIKE $2",
		userID, "%"+query+"%").Scan(&total)

	q, args := b.Build()
	rows, err := DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	var result []models.Channel
	for rows.Next() {
		var ch models.Channel
		var providerConfigID, folderID, teamID, desc sql.NullString
		var settingsJSON []byte
		err := rows.Scan(&ch.ID, &ch.UserID, &ch.Title, &desc, &ch.Type, &ch.Model,
			&ch.SystemPrompt, &providerConfigID, &ch.IsArchived, &ch.IsPinned,
			&folderID, &teamID, &settingsJSON, &ch.CreatedAt, &ch.UpdatedAt)
		if err != nil {
			return nil, 0, err
		}
		ch.Description = NullableString(desc)
		ch.ProviderConfigID = NullableStringPtr(providerConfigID)
		ch.FolderID = NullableStringPtr(folderID)
		ch.TeamID = NullableStringPtr(teamID)
		json.Unmarshal(settingsJSON, &ch.Settings)
		result = append(result, ch)
	}
	return result, total, rows.Err()
}

func (s *ChannelStore) GetCursor(ctx context.Context, channelID, userID string) (*models.ChannelCursor, error) {
	var c models.ChannelCursor
	var leafID sql.NullString
	err := DB.QueryRowContext(ctx, `
		SELECT id, channel_id, user_id, active_leaf_id, updated_at
		FROM channel_cursors WHERE channel_id = $1 AND user_id = $2`,
		channelID, userID).Scan(&c.ID, &c.ChannelID, &c.UserID, &leafID, &c.UpdatedAt)
	if err != nil {
		return nil, err
	}
	c.ActiveLeafID = NullableStringPtr(leafID)
	return &c, nil
}

func (s *ChannelStore) SetCursor(ctx context.Context, channelID, userID, leafID string) error {
	_, err := DB.ExecContext(ctx, `
		INSERT INTO channel_cursors (channel_id, user_id, active_leaf_id)
		VALUES ($1, $2, $3)
		ON CONFLICT (channel_id, user_id) DO UPDATE SET active_leaf_id = $3, updated_at = NOW()`,
		channelID, userID, leafID)
	return err
}

func (s *ChannelStore) SetModel(ctx context.Context, cm *models.ChannelModel) error {
	// For persona entries, use the persona-aware path
	if cm.PersonaID != nil && *cm.PersonaID != "" {
		return s.SetPersonaModel(ctx, cm)
	}
	// Nullable provider_config_id: empty string → SQL NULL (UUID FK)
	var provCfgID interface{} = cm.ProviderConfigID
	if cm.ProviderConfigID == "" {
		provCfgID = nil
	}
	// Raw model upsert (no persona) — matches idx_channel_models_raw partial index
	_, err := DB.ExecContext(ctx, `
		INSERT INTO channel_models (channel_id, model_id, provider_config_id, display_name, system_prompt, settings, is_default)
		VALUES ($1, $2, $3, $4, $5, $6, $7)
		ON CONFLICT (channel_id, model_id, provider_config_id) WHERE persona_id IS NULL DO UPDATE SET
			display_name = $4, system_prompt = $5, settings = $6, is_default = $7`,
		cm.ChannelID, cm.ModelID, provCfgID, cm.DisplayName, cm.SystemPrompt, "{}", cm.IsDefault)
	return err
}

// SetPersonaModel inserts or updates a persona's channel model roster entry.
// Uses the idx_channel_models_persona partial index (one per persona per channel).
func (s *ChannelStore) SetPersonaModel(ctx context.Context, cm *models.ChannelModel) error {
	_, err := DB.ExecContext(ctx, `
		INSERT INTO channel_models (channel_id, model_id, provider_config_id, persona_id, display_name, system_prompt, settings, is_default)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
		ON CONFLICT (channel_id, persona_id) WHERE persona_id IS NOT NULL DO UPDATE SET
			model_id = $2, provider_config_id = $3, display_name = $5, system_prompt = $6, settings = $7, is_default = $8`,
		cm.ChannelID, cm.ModelID, cm.ProviderConfigID, cm.PersonaID, cm.DisplayName, cm.SystemPrompt, "{}", cm.IsDefault)
	return err
}

func (s *ChannelStore) GetModels(ctx context.Context, channelID string) ([]models.ChannelModel, error) {
	rows, err := DB.QueryContext(ctx, `
		SELECT cm.id, cm.channel_id, cm.model_id, COALESCE(cm.provider_config_id::text, ''),
			COALESCE(cm.persona_id::text, ''), COALESCE(p.handle, ''), COALESCE(cm.display_name, ''),
			COALESCE(cm.system_prompt, ''), cm.is_default
		FROM channel_models cm
		LEFT JOIN personas p ON p.id = cm.persona_id
		WHERE cm.channel_id = $1`, channelID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var result []models.ChannelModel
	for rows.Next() {
		var cm models.ChannelModel
		var personaID string
		if err := rows.Scan(&cm.ID, &cm.ChannelID, &cm.ModelID, &cm.ProviderConfigID,
			&personaID, &cm.Handle, &cm.DisplayName, &cm.SystemPrompt, &cm.IsDefault); err != nil {
			return nil, err
		}
		if personaID != "" {
			cm.PersonaID = &personaID
		}
		result = append(result, cm)
	}
	return result, rows.Err()
}

func (s *ChannelStore) GetModelByID(ctx context.Context, id string) (*models.ChannelModel, error) {
	var cm models.ChannelModel
	var personaID string
	err := DB.QueryRowContext(ctx, `
		SELECT cm.id, cm.channel_id, cm.model_id, COALESCE(cm.provider_config_id::text, ''),
			COALESCE(cm.persona_id::text, ''), COALESCE(p.handle, ''), COALESCE(cm.display_name, ''),
			COALESCE(cm.system_prompt, ''), cm.is_default
		FROM channel_models cm
		LEFT JOIN personas p ON p.id = cm.persona_id
		WHERE cm.id = $1`, id).Scan(
		&cm.ID, &cm.ChannelID, &cm.ModelID, &cm.ProviderConfigID,
		&personaID, &cm.Handle, &cm.DisplayName, &cm.SystemPrompt, &cm.IsDefault)
	if err != nil {
		return nil, err
	}
	if personaID != "" {
		cm.PersonaID = &personaID
	}
	return &cm, nil
}

func (s *ChannelStore) UpdateModel(ctx context.Context, id string, fields map[string]interface{}) error {
	if len(fields) == 0 {
		return nil
	}
	// Build SET clause dynamically
	sets := make([]string, 0, len(fields))
	args := make([]interface{}, 0, len(fields)+1)
	i := 1
	for col, val := range fields {
		sets = append(sets, col+" = $"+fmt.Sprintf("%d", i))
		args = append(args, val)
		i++
	}
	args = append(args, id)
	query := "UPDATE channel_models SET " + strings.Join(sets, ", ") + " WHERE id = $" + fmt.Sprintf("%d", i)
	_, err := DB.ExecContext(ctx, query, args...)
	return err
}

func (s *ChannelStore) DeleteModel(ctx context.Context, id string) error {
	res, err := DB.ExecContext(ctx, `DELETE FROM channel_models WHERE id = $1`, id)
	if err != nil {
		return err
	}
	n, _ := res.RowsAffected()
	if n == 0 {
		return sql.ErrNoRows
	}
	return nil
}

func (s *ChannelStore) UserOwns(ctx context.Context, channelID, userID string) (bool, error) {
	var exists bool
	err := DB.QueryRowContext(ctx,
		"SELECT EXISTS(SELECT 1 FROM channels WHERE id = $1 AND user_id = $2)",
		channelID, userID).Scan(&exists)
	return exists, err
}

// ResolveWorkspaceID returns the effective workspace for a channel.
// Resolution: channel.workspace_id > project.workspace_id.
// Returns empty string if no workspace is bound.
func (s *ChannelStore) ResolveWorkspaceID(ctx context.Context, channelID string) (string, error) {
	var wsID sql.NullString
	err := DB.QueryRowContext(ctx, `
		SELECT COALESCE(c.workspace_id, p.workspace_id)
		FROM channels c
		LEFT JOIN project_channels pc ON pc.channel_id = c.id
		LEFT JOIN projects p ON p.id = pc.project_id
		WHERE c.id = $1
		LIMIT 1`, channelID).Scan(&wsID)
	if err != nil {
		if err == sql.ErrNoRows {
			return "", nil
		}
		return "", err
	}
	return NullableString(wsID), nil
}

// ── Channel Participants (ICD §3.7) ──────────

func (s *ChannelStore) AddParticipant(ctx context.Context, p *models.ChannelParticipant) error {
	_, err := DB.ExecContext(ctx, `
		INSERT INTO channel_participants (channel_id, participant_type, participant_id, role, display_name, avatar_url)
		VALUES ($1, $2, $3, $4, $5, $6)`,
		p.ChannelID, p.ParticipantType, p.ParticipantID, p.Role, p.DisplayName, p.AvatarURL)
	return err
}

func (s *ChannelStore) ListParticipants(ctx context.Context, channelID string) ([]models.ChannelParticipant, error) {
	rows, err := DB.QueryContext(ctx, `
		SELECT cp.id, cp.channel_id, cp.participant_type, cp.participant_id, cp.role,
			COALESCE(NULLIF(cp.display_name,''), NULLIF(u.display_name,''), u.username) AS display_name,
			COALESCE(NULLIF(cp.avatar_url,''), u.avatar_url) AS avatar_url,
			cp.joined_at
		FROM channel_participants cp
		LEFT JOIN users u ON cp.participant_type = 'user' AND cp.participant_id = u.id
		WHERE cp.channel_id = $1 ORDER BY cp.joined_at`, channelID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var result []models.ChannelParticipant
	for rows.Next() {
		var p models.ChannelParticipant
		if err := rows.Scan(&p.ID, &p.ChannelID, &p.ParticipantType, &p.ParticipantID,
			&p.Role, &p.DisplayName, &p.AvatarURL, &p.JoinedAt); err != nil {
			return nil, err
		}
		result = append(result, p)
	}
	return result, rows.Err()
}

func (s *ChannelStore) GetParticipantByID(ctx context.Context, id string) (*models.ChannelParticipant, error) {
	var p models.ChannelParticipant
	err := DB.QueryRowContext(ctx, `
		SELECT id, channel_id, participant_type, participant_id, role,
			display_name, avatar_url, joined_at
		FROM channel_participants WHERE id = $1`, id).Scan(
		&p.ID, &p.ChannelID, &p.ParticipantType, &p.ParticipantID,
		&p.Role, &p.DisplayName, &p.AvatarURL, &p.JoinedAt)
	if err != nil {
		return nil, err
	}
	return &p, nil
}

func (s *ChannelStore) UpdateParticipantRole(ctx context.Context, id, role string) error {
	_, err := DB.ExecContext(ctx, `UPDATE channel_participants SET role = $1 WHERE id = $2`, role, id)
	return err
}

func (s *ChannelStore) RemoveParticipant(ctx context.Context, id string) error {
	res, err := DB.ExecContext(ctx, `DELETE FROM channel_participants WHERE id = $1`, id)
	if err != nil {
		return err
	}
	n, _ := res.RowsAffected()
	if n == 0 {
		return sql.ErrNoRows
	}
	return nil
}

func (s *ChannelStore) IsParticipant(ctx context.Context, channelID, pType, pID string) (bool, error) {
	var exists bool
	err := DB.QueryRowContext(ctx, `
		SELECT EXISTS(SELECT 1 FROM channel_participants
			WHERE channel_id = $1 AND participant_type = $2 AND participant_id = $3)`,
		channelID, pType, pID).Scan(&exists)
	return exists, err
}

func (s *ChannelStore) GetParticipantRole(ctx context.Context, channelID, pType, pID string) (string, error) {
	var role string
	err := DB.QueryRowContext(ctx, `
		SELECT role FROM channel_participants
		WHERE channel_id = $1 AND participant_type = $2 AND participant_id = $3`,
		channelID, pType, pID).Scan(&role)
	return role, err
}

func (s *ChannelStore) CountParticipantsByRole(ctx context.Context, channelID, role string) (int, error) {
	var count int
	err := DB.QueryRowContext(ctx, `
		SELECT COUNT(*) FROM channel_participants WHERE channel_id = $1 AND role = $2`,
		channelID, role).Scan(&count)
	return count, err
}

func (s *ChannelStore) DeleteModelByPersona(ctx context.Context, channelID, personaID string) error {
	_, err := DB.ExecContext(ctx,
		`DELETE FROM channel_models WHERE channel_id = $1 AND persona_id = $2`,
		channelID, personaID)
	return err
}

// ── Admin: Archived Channel Management ──────

func (s *ChannelStore) ListArchived(ctx context.Context, opts store.ListOptions) ([]store.ArchivedChannel, int, error) {
	// Count
	var total int
	DB.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM channels WHERE is_archived = true`).Scan(&total)

	rows, err := DB.QueryContext(ctx, `
		SELECT c.id, c.title, c.type, COALESCE(u.username, '') AS owner_name,
		       c.updated_at,
		       (SELECT COUNT(*) FROM messages WHERE channel_id = c.id) AS message_count
		FROM channels c
		LEFT JOIN users u ON u.id = c.user_id
		WHERE c.is_archived = true
		ORDER BY c.updated_at DESC
		LIMIT $1 OFFSET $2`, opts.Limit, opts.Offset)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	var channels []store.ArchivedChannel
	for rows.Next() {
		var ch store.ArchivedChannel
		if rows.Scan(&ch.ID, &ch.Title, &ch.Type, &ch.OwnerName, &ch.UpdatedAt, &ch.MessageCount) == nil {
			channels = append(channels, ch)
		}
	}
	if channels == nil {
		channels = []store.ArchivedChannel{}
	}
	return channels, total, rows.Err()
}

func (s *ChannelStore) Purge(ctx context.Context, id string) error {
	// Verify the channel is actually archived
	var isArchived bool
	err := DB.QueryRowContext(ctx,
		`SELECT is_archived FROM channels WHERE id = $1`, id).Scan(&isArchived)
	if err != nil {
		return fmt.Errorf("channel not found")
	}
	if !isArchived {
		return fmt.Errorf("channel must be archived before purging")
	}

	// Hard delete (CASCADE removes messages, participants, models)
	_, err = DB.ExecContext(ctx, `DELETE FROM channels WHERE id = $1`, id)
	return err
}
// ── CS1 additions (v0.29.0) ─────────────────────────────────────────────

func (s *ChannelStore) FindExistingDM(ctx context.Context, userID1, userID2 string) (string, error) {
	var channelID string
	err := DB.QueryRowContext(ctx, `
		SELECT cp1.channel_id FROM channel_participants cp1
		JOIN channel_participants cp2 ON cp1.channel_id = cp2.channel_id
		JOIN channels c ON c.id = cp1.channel_id
		WHERE c.type = 'dm'
		  AND cp1.participant_type = 'user' AND cp1.participant_id = $1
		  AND cp2.participant_type = 'user' AND cp2.participant_id = $2
		LIMIT 1
	`, userID1, userID2).Scan(&channelID)
	if err == sql.ErrNoRows {
		return "", nil
	}
	return channelID, err
}

func (s *ChannelStore) GetUnreadCount(ctx context.Context, channelID, userID string) (int, error) {
	var count int
	err := DB.QueryRowContext(ctx, `
		SELECT COUNT(*) FROM messages m
		JOIN channel_participants cp ON cp.channel_id = m.channel_id
		WHERE cp.channel_id = $1
		  AND cp.participant_type = 'user' AND cp.participant_id = $2
		  AND m.created_at > cp.last_read_at
	`, channelID, userID).Scan(&count)
	return count, err
}

func (s *ChannelStore) DeleteByOwner(ctx context.Context, channelID, userID string) (int64, error) {
	result, err := DB.ExecContext(ctx,
		`DELETE FROM channels WHERE id = $1 AND user_id = $2`,
		channelID, userID)
	if err != nil {
		return 0, err
	}
	return result.RowsAffected()
}

func (s *ChannelStore) ArchiveForRetention(ctx context.Context, channelID string, purgeAfter time.Time) error {
	_, err := DB.ExecContext(ctx, `
		UPDATE channels SET is_archived = true, purge_after = $2, updated_at = NOW()
		WHERE id = $1
	`, channelID, purgeAfter)
	return err
}

func (s *ChannelStore) ListPurgeable(ctx context.Context) ([]string, error) {
	rows, err := DB.QueryContext(ctx, `
		SELECT id FROM channels WHERE purge_after IS NOT NULL AND purge_after <= NOW()
	`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var ids []string
	for rows.Next() {
		var id string
		if rows.Scan(&id) == nil {
			ids = append(ids, id)
		}
	}
	return ids, rows.Err()
}

func (s *ChannelStore) MarkRead(ctx context.Context, channelID, userID string) error {
	// Update last_read_at
	_, err := DB.ExecContext(ctx, `
		UPDATE channel_participants
		SET last_read_at = NOW()
		WHERE channel_id = $1 AND participant_type = 'user' AND participant_id = $2
	`, channelID, userID)
	if err != nil {
		return nil // participant may not exist for legacy chats
	}

	// Best-effort: update last_read_message_id
	var latestMsgID *string
	_ = DB.QueryRowContext(ctx, `
		SELECT id FROM messages WHERE channel_id = $1 ORDER BY created_at DESC LIMIT 1
	`, channelID).Scan(&latestMsgID)
	if latestMsgID != nil {
		_, _ = DB.ExecContext(ctx, `
			UPDATE channel_participants
			SET last_read_message_id = $1
			WHERE channel_id = $2 AND participant_type = 'user' AND participant_id = $3
		`, *latestMsgID, channelID, userID)
	}

	return nil
}

func (s *ChannelStore) CountParticipantsByType(ctx context.Context, channelID, pType string) (int, error) {
	var count int
	err := DB.QueryRowContext(ctx, `
		SELECT COUNT(*) FROM channel_participants
		WHERE channel_id = $1 AND participant_type = $2
	`, channelID, pType).Scan(&count)
	return count, err
}

// ── CS2 additions (v0.29.0) ─────────────────────────────────────────────

func (s *ChannelStore) CountAll(ctx context.Context) (int, error) {
	var count int
	err := DB.QueryRowContext(ctx, "SELECT COUNT(*) FROM channels").Scan(&count)
	return count, err
}

// ── Workflow instance state (v0.29.0-cs3) ───────────────────────────────

func (s *ChannelStore) SetWorkflowInstance(ctx context.Context, channelID, workflowID string, version int, stageData json.RawMessage, status string) error {
	now := time.Now().UTC()
	_, err := DB.ExecContext(ctx, `
		UPDATE channels
		SET workflow_id = $1, workflow_version = $2, current_stage = 0,
		    stage_data = $3, workflow_status = $4, last_activity_at = $5,
		    stage_entered_at = $6
		WHERE id = $7
	`, workflowID, version, stageData, status, now, now, channelID)
	return err
}

func (s *ChannelStore) GetWorkflowStatus(ctx context.Context, channelID string) (*store.WorkflowChannelStatus, error) {
	var ws store.WorkflowChannelStatus
	var stageData []byte
	err := DB.QueryRowContext(ctx, `
		SELECT workflow_id, workflow_version, current_stage,
		       COALESCE(stage_data, '{}'), COALESCE(workflow_status, 'active'),
		       last_activity_at, stage_entered_at
		FROM channels WHERE id = $1 AND type = 'workflow'
	`, channelID).Scan(&ws.WorkflowID, &ws.WorkflowVersion,
		&ws.CurrentStage, &stageData, &ws.Status, &ws.LastActivityAt, &ws.StageEnteredAt)
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	ws.StageData = stageData
	return &ws, nil
}

func (s *ChannelStore) AdvanceWorkflowStage(ctx context.Context, channelID string, nextStage int, stageData json.RawMessage) error {
	now := time.Now().UTC()
	_, err := DB.ExecContext(ctx, `
		UPDATE channels
		SET current_stage = $1, stage_data = $2, last_activity_at = $3,
		    stage_entered_at = $4
		WHERE id = $5
	`, nextStage, stageData, now, now, channelID)
	return err
}

func (s *ChannelStore) CompleteWorkflow(ctx context.Context, channelID string, finalStage int, stageData json.RawMessage) error {
	_, err := DB.ExecContext(ctx, `
		UPDATE channels
		SET current_stage = $1, workflow_status = 'completed',
		    stage_data = $2, last_activity_at = $3, ai_mode = 'off'
		WHERE id = $4
	`, finalStage, stageData, time.Now().UTC(), channelID)
	return err
}

func (s *ChannelStore) CancelWorkflow(ctx context.Context, channelID string) error {
	_, err := DB.ExecContext(ctx, `
		UPDATE channels
		SET workflow_status = 'cancelled', ai_mode = 'off', last_activity_at = $1
		WHERE id = $2 AND type = 'workflow'
	`, time.Now().UTC(), channelID)
	return err
}

func (s *ChannelStore) RejectWorkflowToStage(ctx context.Context, channelID string, stage int) error {
	now := time.Now().UTC()
	_, err := DB.ExecContext(ctx, `
		UPDATE channels SET current_stage = $1, last_activity_at = $2,
		       stage_entered_at = $3 WHERE id = $4
	`, stage, now, now, channelID)
	return err
}

func (s *ChannelStore) GetStageData(ctx context.Context, channelID string) (json.RawMessage, error) {
	var data json.RawMessage
	err := DB.QueryRowContext(ctx, `
		SELECT COALESCE(stage_data, '{}') FROM channels WHERE id = $1
	`, channelID).Scan(&data)
	return data, err
}

// ── Background job helpers (v0.29.0-cs4) ────────────────────────────────

func (s *ChannelStore) MarkStaleWorkflows(ctx context.Context, cutoff time.Time) (int64, error) {
	result, err := DB.ExecContext(ctx, `
		UPDATE channels
		SET workflow_status = 'stale'
		WHERE type = 'workflow'
		  AND workflow_status = 'active'
		  AND last_activity_at < $1
	`, cutoff)
	if err != nil {
		return 0, err
	}
	return result.RowsAffected()
}

func (s *ChannelStore) EnforceWorkflowRetention(ctx context.Context) (int64, error) {
	result, err := DB.ExecContext(ctx, `
		DELETE FROM channels
		WHERE type = 'workflow'
		  AND workflow_status IN ('completed', 'archived')
		  AND workflow_id IS NOT NULL
		  AND workflow_id IN (
		    SELECT id FROM workflows
		    WHERE retention IS NOT NULL
		      AND retention->>'mode' = 'delete'
		      AND (retention->>'delete_after_days')::int > 0
		      AND channels.last_activity_at < now() - ((retention->>'delete_after_days')::int || ' days')::interval
		  )
	`)
	if err != nil {
		return 0, err
	}
	return result.RowsAffected()
}

func (s *ChannelStore) GetTypeAndAllowAnonymous(ctx context.Context, channelID string) (string, bool, error) {
	var chType string
	var allowAnon bool
	err := DB.QueryRowContext(ctx,
		`SELECT type, allow_anonymous FROM channels WHERE id = $1`, channelID).Scan(&chType, &allowAnon)
	return chType, allowAnon, err
}

// ── CS5b additions (v0.29.0) ────────────────────────────────────────────

func (s *ChannelStore) FindCompactionCandidates(ctx context.Context, activityBefore, createdAfter time.Time, minMessages, minChars, limit int) ([]models.Channel, error) {
	rows, err := DB.QueryContext(ctx, `
		SELECT c.id, c.user_id, COALESCE(c.model, ''), COALESCE(c.settings::text, '{}'),
		       COUNT(m.id) AS msg_count,
		       COALESCE(SUM(LENGTH(m.content)), 0) AS total_chars
		FROM channels c
		JOIN messages m ON m.channel_id = c.id AND m.deleted_at IS NULL
		WHERE c.type = 'direct'
		  AND c.is_archived = false
		  AND c.updated_at < $1
		  AND c.updated_at > $2
		GROUP BY c.id
		HAVING COUNT(m.id) >= $3
		   AND COALESCE(SUM(LENGTH(m.content)), 0) > $4
		ORDER BY c.updated_at DESC
		LIMIT $5
	`, activityBefore, createdAfter, minMessages, minChars, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var result []models.Channel
	for rows.Next() {
		var ch models.Channel
		var settingsRaw string
		var msgCount, totalChars int
		if err := rows.Scan(&ch.ID, &ch.UserID, &ch.Model, &settingsRaw, &msgCount, &totalChars); err != nil {
			continue
		}
		ch.Settings = models.JSONMap{}
		_ = json.Unmarshal([]byte(settingsRaw), &ch.Settings)
		result = append(result, ch)
	}
	if result == nil {
		result = []models.Channel{}
	}
	return result, rows.Err()
}

// ── CS7a additions (v0.29.0) ────────────────────────────────────────────

func (s *ChannelStore) GetProviderConfigID(ctx context.Context, channelID string) (*string, error) {
	var configID sql.NullString
	err := DB.QueryRowContext(ctx,
		`SELECT provider_config_id FROM channels WHERE id = $1`, channelID).Scan(&configID)
	if err != nil {
		return nil, err
	}
	return NullableStringPtr(configID), nil
}

func (s *ChannelStore) UserCanAccess(ctx context.Context, channelID, userID string) (bool, error) {
	var ok bool
	err := DB.QueryRowContext(ctx, `
		SELECT EXISTS(
			SELECT 1 FROM channels WHERE id = $1 AND user_id = $2
			UNION ALL
			SELECT 1 FROM channel_participants
			WHERE channel_id = $1 AND participant_type = 'user' AND participant_id = $2
			LIMIT 1
		)`, channelID, userID).Scan(&ok)
	return ok, err
}

// ── CS7b additions (v0.29.0) ────────────────────────────────────────────

const channelListCols = `c.id, c.user_id, c.title, c.type, c.ai_mode, c.topic,
	c.description, c.model, c.provider_config_id,
	c.system_prompt, c.is_archived, c.is_pinned, c.folder, c.folder_id, c.project_id, c.workspace_id,
	c.tags, c.settings,
	COALESCE(mc.cnt, 0) AS message_count,
	c.created_at, c.updated_at`

const channelListFrom = `channels c
	LEFT JOIN (
		SELECT channel_id, COUNT(*) AS cnt FROM messages WHERE deleted_at IS NULL GROUP BY channel_id
	) mc ON mc.channel_id = c.id`

func (s *ChannelStore) ListFiltered(ctx context.Context, userID string, f store.ChannelListFilter) ([]store.ChannelListItem, int, error) {
	b := NewSelect(channelListCols, channelListFrom)
	b.Where("(c.user_id = ? OR c.id IN (SELECT channel_id FROM channel_participants WHERE participant_type = 'user' AND participant_id = ?))", userID, userID)
	b.Where("c.is_archived = ?", f.Archived)

	if len(f.Types) == 1 {
		b.Where("c.type = ?", f.Types[0])
	} else if len(f.Types) > 1 {
		placeholders := make([]string, len(f.Types))
		for i, t := range f.Types {
			b.argIdx++
			placeholders[i] = fmt.Sprintf("$%d", b.argIdx)
			b.args = append(b.args, t)
		}
		b.WhereRaw("c.type IN (" + strings.Join(placeholders, ",") + ")")
	}
	if f.Folder != "" {
		b.Where("c.folder = ?", f.Folder)
	}
	if f.FolderID != "" {
		b.Where("c.folder_id = ?", f.FolderID)
	}
	if f.Search != "" {
		b.Where("c.title ILIKE ?", "%"+f.Search+"%")
	}
	if f.ProjectID == "none" {
		b.WhereRaw("c.project_id IS NULL")
	} else if f.ProjectID != "" {
		b.Where("c.project_id = ?", f.ProjectID)
	}

	// Count
	countQ, countArgs := b.CountBuild()
	var total int
	DB.QueryRowContext(ctx, countQ, countArgs...).Scan(&total)

	b.OrderBy("c.is_pinned DESC, c.updated_at", "DESC")
	b.Paginate(f.ListOptions)

	q, args := b.Build()
	rows, err := DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	items, err := scanChannelListItems(rows)
	if err != nil {
		return nil, 0, err
	}

	// Compute unread counts
	for i := range items {
		DB.QueryRowContext(ctx, `
			SELECT COUNT(*) FROM messages m
			JOIN channel_participants cp ON cp.channel_id = m.channel_id
			WHERE cp.channel_id = $1
			  AND cp.participant_type = 'user' AND cp.participant_id = $2
			  AND m.created_at > cp.last_read_at
			  AND m.deleted_at IS NULL
		`, items[i].ID, userID).Scan(&items[i].UnreadCount)
	}

	return items, total, nil
}

func (s *ChannelStore) GetForUser(ctx context.Context, channelID, userID string) (*store.ChannelListItem, error) {
	row := DB.QueryRowContext(ctx, fmt.Sprintf(`
		SELECT %s FROM %s
		WHERE c.id = $1 AND (c.user_id = $2 OR c.id IN (
			SELECT channel_id FROM channel_participants WHERE participant_type = 'user' AND participant_id = $2
		))
	`, channelListCols, channelListFrom), channelID, userID)

	var item store.ChannelListItem
	var tags []byte
	var settings []byte
	err := row.Scan(
		&item.ID, &item.UserID, &item.Title, &item.Type, &item.AiMode, &item.Topic,
		&item.Description, &item.Model, &item.ProviderConfigID,
		&item.SystemPrompt, &item.IsArchived, &item.IsPinned, &item.Folder, &item.FolderID, &item.ProjectID, &item.WorkspaceID,
		&tags, &settings,
		&item.MessageCount, &item.CreatedAtTime, &item.UpdatedAtTime,
	)
	if err != nil {
		return nil, err
	}
	item.Tags = scanTagsBytes(tags)
	item.Settings = safeJSONBytes(settings)
	item.CreatedAt = item.CreatedAtTime.Format("2006-01-02T15:04:05Z")
	item.UpdatedAt = item.UpdatedAtTime.Format("2006-01-02T15:04:05Z")
	return &item, nil
}

func (s *ChannelStore) CreateFull(ctx context.Context, ch *models.Channel, folder string, tags []string, aiMode string,
	ownerUserID string, dmPartnerIDs []string, defaultModel, defaultConfigID string) error {
	tx, err := DB.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()

	if tags == nil {
		tags = []string{}
	}

	// Insert channel
	err = tx.QueryRowContext(ctx, `
		INSERT INTO channels (user_id, title, type, description, model, system_prompt,
			provider_config_id, folder, folder_id, tags, ai_mode)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
		RETURNING id, created_at, updated_at`,
		ch.UserID, ch.Title, ch.Type, ch.Description, ch.Model, ch.SystemPrompt,
		models.NullString(ch.ProviderConfigID), folder, models.NullString(ch.FolderID),
		pq.Array(tags), aiMode,
	).Scan(&ch.ID, &ch.CreatedAt, &ch.UpdatedAt)
	if err != nil {
		return fmt.Errorf("CreateFull insert channel: %w", err)
	}

	// Add owner participant
	_, err = tx.ExecContext(ctx, `
		INSERT INTO channel_participants (channel_id, participant_type, participant_id, role)
		VALUES ($1, 'user', $2, 'owner')
		ON CONFLICT DO NOTHING`, ch.ID, ownerUserID)
	if err != nil {
		return fmt.Errorf("CreateFull add owner: %w", err)
	}

	// Add DM partner participants
	for _, pid := range dmPartnerIDs {
		if pid == ownerUserID {
			continue
		}
		_, _ = tx.ExecContext(ctx, `
			INSERT INTO channel_participants (channel_id, participant_type, participant_id, role)
			VALUES ($1, 'user', $2, 'member')
			ON CONFLICT DO NOTHING`, ch.ID, pid)
	}

	// Auto-create channel_model if model specified
	if defaultModel != "" {
		_, _ = tx.ExecContext(ctx, `
			INSERT INTO channel_models (channel_id, model_id, provider_config_id, is_default)
			VALUES ($1, $2, $3, true)
			ON CONFLICT DO NOTHING`, ch.ID, defaultModel, models.NullString(&defaultConfigID))
	}

	return tx.Commit()
}

func (s *ChannelStore) MergeSettings(ctx context.Context, channelID string, settingsJSON json.RawMessage) error {
	_, err := DB.ExecContext(ctx,
		`UPDATE channels SET settings = COALESCE(settings, '{}'::jsonb) || $1::jsonb WHERE id = $2`,
		[]byte(settingsJSON), channelID)
	return err
}

// ── Monitoring (v0.35.0) ────────────────────

func (s *ChannelStore) ListByType(ctx context.Context, channelType string) ([]models.Channel, error) {
	rows, err := DB.QueryContext(ctx, `
		SELECT id, user_id, title, COALESCE(description, ''), type,
		       team_id, created_at
		FROM channels WHERE type = $1
		ORDER BY created_at DESC`, channelType)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var result []models.Channel
	for rows.Next() {
		var ch models.Channel
		if err := rows.Scan(&ch.ID, &ch.UserID, &ch.Title, &ch.Description,
			&ch.Type, &ch.TeamID, &ch.CreatedAt); err != nil {
			return nil, err
		}
		result = append(result, ch)
	}
	return result, rows.Err()
}

// ── CS7b helpers ────────────────────────────

func scanChannelListItems(rows *sql.Rows) ([]store.ChannelListItem, error) {
	var result []store.ChannelListItem
	for rows.Next() {
		var item store.ChannelListItem
		var tags []byte
		var settings []byte
		err := rows.Scan(
			&item.ID, &item.UserID, &item.Title, &item.Type, &item.AiMode, &item.Topic,
			&item.Description, &item.Model, &item.ProviderConfigID,
			&item.SystemPrompt, &item.IsArchived, &item.IsPinned, &item.Folder, &item.FolderID, &item.ProjectID, &item.WorkspaceID,
			&tags, &settings,
			&item.MessageCount, &item.CreatedAtTime, &item.UpdatedAtTime,
		)
		if err != nil {
			return nil, err
		}
		item.Tags = scanTagsBytes(tags)
		item.Settings = safeJSONBytes(settings)
		item.CreatedAt = item.CreatedAtTime.Format("2006-01-02T15:04:05Z")
		item.UpdatedAt = item.UpdatedAtTime.Format("2006-01-02T15:04:05Z")
		result = append(result, item)
	}
	return result, rows.Err()
}

func scanTagsBytes(b []byte) []string {
	if len(b) == 0 {
		return []string{}
	}
	// Try JSON array first (SQLite path), then PG text[] format
	var arr []string
	if json.Unmarshal(b, &arr) == nil {
		if arr == nil {
			return []string{}
		}
		return arr
	}
	// PG text[] format: {tag1,tag2}
	s := strings.TrimPrefix(strings.TrimSuffix(string(b), "}"), "{")
	if s == "" {
		return []string{}
	}
	return strings.Split(s, ",")
}

func safeJSONBytes(b []byte) json.RawMessage {
	if len(b) == 0 || !json.Valid(b) {
		return json.RawMessage("{}")
	}
	cp := make([]byte, len(b))
	copy(cp, b)
	return json.RawMessage(cp)
}