package sqlite

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

	"git.gobha.me/xcaliber/chat-switchboard/models"
	"git.gobha.me/xcaliber/chat-switchboard/store"
)

type ChannelStore struct{}

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

func (s *ChannelStore) Create(ctx context.Context, ch *models.Channel) error {
	ch.ID = store.NewID()
	now := time.Now().UTC()
	ch.CreatedAt = now
	ch.UpdatedAt = now
	_, err := DB.ExecContext(ctx, `
		INSERT INTO channels (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)
		VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)`,
		ch.ID, 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),
		now.Format(timeFmt), now.Format(timeFmt),
	)
	return err
}

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 = ?`, id).Scan(
		&ch.ID, &ch.UserID, &ch.Title, &desc, &ch.Type, &ch.Model, &ch.SystemPrompt,
		&providerConfigID, &ch.IsArchived, &ch.IsPinned, &folderID, &teamID, &settingsJSON,
		st(&ch.CreatedAt), st(&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 = ?", 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 = ?", 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, st(&ch.CreatedAt), st(&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 LIKE ?", "%"+query+"%")
	b.OrderBy("updated_at", "DESC")
	b.Paginate(opts)

	var total int
	DB.QueryRowContext(ctx,
		"SELECT COUNT(*) FROM channels WHERE user_id = ? AND title LIKE ?",
		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, st(&ch.CreatedAt), st(&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 = ? AND user_id = ?`,
		channelID, userID).Scan(&c.ID, &c.ChannelID, &c.UserID, &leafID, st(&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 (id, channel_id, user_id, active_leaf_id)
		VALUES (?, ?, ?, ?)
		ON CONFLICT (channel_id, user_id) DO UPDATE SET active_leaf_id = excluded.active_leaf_id, updated_at = datetime('now')`,
		store.NewID(), 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 (id, channel_id, model_id, provider_config_id, display_name, system_prompt, settings, is_default)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?)
		ON CONFLICT (channel_id, model_id, provider_config_id) WHERE persona_id IS NULL DO UPDATE SET
			display_name = excluded.display_name, system_prompt = excluded.system_prompt, settings = excluded.settings, is_default = excluded.is_default`,
		store.NewID(), cm.ChannelID, cm.ModelID, provCfgID, cm.DisplayName, cm.SystemPrompt, "{}", cm.IsDefault)
	return err
}

// SetPersonaModel inserts or updates a persona's channel model roster entry.
func (s *ChannelStore) SetPersonaModel(ctx context.Context, cm *models.ChannelModel) error {
	_, err := DB.ExecContext(ctx, `
		INSERT INTO channel_models (id, channel_id, model_id, provider_config_id, persona_id, display_name, system_prompt, settings, is_default)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
		ON CONFLICT (channel_id, persona_id) WHERE persona_id IS NOT NULL DO UPDATE SET
			model_id = excluded.model_id, provider_config_id = excluded.provider_config_id, display_name = excluded.display_name, system_prompt = excluded.system_prompt, settings = excluded.settings, is_default = excluded.is_default`,
		store.NewID(), 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, ''),
			COALESCE(cm.persona_id, ''), 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 = ?`, 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, ''),
			COALESCE(cm.persona_id, ''), 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 = ?`, 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
	}
	sets := make([]string, 0, len(fields))
	args := make([]interface{}, 0, len(fields)+1)
	for col, val := range fields {
		sets = append(sets, col+" = ?")
		args = append(args, val)
	}
	args = append(args, id)
	query := "UPDATE channel_models SET " + strings.Join(sets, ", ") + " WHERE id = ?"
	_, 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 = ?`, 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 = ? AND user_id = ?)",
		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 = ?
		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 (id, channel_id, participant_type, participant_id, role, display_name, avatar_url)
		VALUES (?, ?, ?, ?, ?, ?, ?)`,
		store.NewID(), 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 id, channel_id, participant_type, participant_id, role,
			display_name, avatar_url, joined_at
		FROM channel_participants WHERE channel_id = ? ORDER BY joined_at`, channelID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var result []models.ChannelParticipant
	for rows.Next() {
		var p models.ChannelParticipant
		var joinedStr string
		if err := rows.Scan(&p.ID, &p.ChannelID, &p.ParticipantType, &p.ParticipantID,
			&p.Role, &p.DisplayName, &p.AvatarURL, &joinedStr); err != nil {
			return nil, err
		}
		p.JoinedAt, _ = time.Parse("2006-01-02 15:04:05", joinedStr)
		result = append(result, p)
	}
	return result, rows.Err()
}

func (s *ChannelStore) GetParticipantByID(ctx context.Context, id string) (*models.ChannelParticipant, error) {
	var p models.ChannelParticipant
	var joinedStr string
	err := DB.QueryRowContext(ctx, `
		SELECT id, channel_id, participant_type, participant_id, role,
			display_name, avatar_url, joined_at
		FROM channel_participants WHERE id = ?`, id).Scan(
		&p.ID, &p.ChannelID, &p.ParticipantType, &p.ParticipantID,
		&p.Role, &p.DisplayName, &p.AvatarURL, &joinedStr)
	if err != nil {
		return nil, err
	}
	p.JoinedAt, _ = time.Parse("2006-01-02 15:04:05", joinedStr)
	return &p, nil
}

func (s *ChannelStore) UpdateParticipantRole(ctx context.Context, id, role string) error {
	_, err := DB.ExecContext(ctx, `UPDATE channel_participants SET role = ? WHERE id = ?`, 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 = ?`, 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 count int
	err := DB.QueryRowContext(ctx, `
		SELECT COUNT(*) FROM channel_participants
		WHERE channel_id = ? AND participant_type = ? AND participant_id = ?`,
		channelID, pType, pID).Scan(&count)
	return count > 0, 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 = ? AND participant_type = ? AND participant_id = ?`,
		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 = ? AND role = ?`,
		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 = ? AND persona_id = ?`,
		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 = 1`).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 = 1
		ORDER BY c.updated_at DESC
		LIMIT ? OFFSET ?`, 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 int
	err := DB.QueryRowContext(ctx,
		`SELECT is_archived FROM channels WHERE id = ?`, id).Scan(&isArchived)
	if err != nil {
		return fmt.Errorf("channel not found")
	}
	if isArchived == 0 {
		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 = ?`, 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 = ?
		  AND cp2.participant_type = 'user' AND cp2.participant_id = ?
		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 = ?
		  AND cp.participant_type = 'user' AND cp.participant_id = ?
		  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 = ? AND user_id = ?`,
		channelID, userID)
	if err != nil {
		return 0, err
	}
	return result.RowsAffected()
}

func (s *ChannelStore) MarkRead(ctx context.Context, channelID, userID string) error {
	_, err := DB.ExecContext(ctx, `
		UPDATE channel_participants
		SET last_read_at = datetime('now')
		WHERE channel_id = ? AND participant_type = 'user' AND participant_id = ?
	`, channelID, userID)
	if err != nil {
		return nil
	}

	var latestMsgID *string
	_ = DB.QueryRowContext(ctx, `
		SELECT id FROM messages WHERE channel_id = ? ORDER BY created_at DESC LIMIT 1
	`, channelID).Scan(&latestMsgID)
	if latestMsgID != nil {
		_, _ = DB.ExecContext(ctx, `
			UPDATE channel_participants
			SET last_read_message_id = ?
			WHERE channel_id = ? AND participant_type = 'user' AND participant_id = ?
		`, *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 = ? AND participant_type = ?
	`, 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 {
	_, err := DB.ExecContext(ctx, `
		UPDATE channels
		SET workflow_id = ?, workflow_version = ?, current_stage = 0,
		    stage_data = ?, workflow_status = ?, last_activity_at = ?
		WHERE id = ?
	`, workflowID, version, stageData, status, time.Now().UTC().Format(timeFmt), 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
		FROM channels WHERE id = ? AND type = 'workflow'
	`, channelID).Scan(&ws.WorkflowID, &ws.WorkflowVersion,
		&ws.CurrentStage, &stageData, &ws.Status, &ws.LastActivityAt)
	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 {
	_, err := DB.ExecContext(ctx, `
		UPDATE channels
		SET current_stage = ?, stage_data = ?, last_activity_at = ?
		WHERE id = ?
	`, nextStage, stageData, time.Now().UTC().Format(timeFmt), 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 = ?, workflow_status = 'completed',
		    stage_data = ?, last_activity_at = ?, ai_mode = 'off'
		WHERE id = ?
	`, finalStage, stageData, time.Now().UTC().Format(timeFmt), channelID)
	return err
}

func (s *ChannelStore) RejectWorkflowToStage(ctx context.Context, channelID string, stage int) error {
	_, err := DB.ExecContext(ctx, `
		UPDATE channels SET current_stage = ?, last_activity_at = ? WHERE id = ?
	`, stage, time.Now().UTC().Format(timeFmt), 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 = ?
	`, 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 < ?
	`, cutoff.Format(timeFmt))
	if err != nil {
		return 0, err
	}
	return result.RowsAffected()
}

func (s *ChannelStore) EnforceWorkflowRetention(ctx context.Context) (int64, error) {
	// SQLite doesn't support JSON operators for retention policy evaluation.
	// This is a no-op on SQLite; retention enforcement is PG-only.
	return 0, nil
}

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 = ?`, 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) {
	// Auto-compaction scanner is PG-only (uses settings::text cast).
	return []models.Channel{}, nil
}

// ── 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 = ?`, 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 = ? AND user_id = ?
			UNION ALL
			SELECT 1 FROM channel_participants
			WHERE channel_id = ? AND participant_type = 'user' AND participant_id = ?
			LIMIT 1
		)`, channelID, userID, 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)
	archivedVal := 0
	if f.Archived {
		archivedVal = 1
	}
	b.Where("c.is_archived = ?", archivedVal)

	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 {
			placeholders[i] = "?"
			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 LIKE ?", "%"+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 = ?
			  AND cp.participant_type = 'user' AND cp.participant_id = ?
			  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 = ? AND (c.user_id = ? OR c.id IN (
			SELECT channel_id FROM channel_participants WHERE participant_type = 'user' AND participant_id = ?
		))
	`, channelListCols, channelListFrom), channelID, userID, userID)

	var item store.ChannelListItem
	var tags, settings string
	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, st(&item.CreatedAtTime), st(&item.UpdatedAtTime),
	)
	if err != nil {
		return nil, err
	}
	item.Tags = ScanArray(tags)
	if item.Tags == nil {
		item.Tags = []string{}
	}
	item.Settings = safeJSONString(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 {
	ch.ID = store.NewID()
	now := time.Now().UTC()
	ch.CreatedAt = now
	ch.UpdatedAt = now

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

	tx, err := DB.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()

	tagsJSON := ArrayToJSON(tags)
	_, err = tx.ExecContext(ctx, `
		INSERT INTO channels (id, user_id, title, type, description, model, system_prompt,
			provider_config_id, folder, folder_id, tags, ai_mode, created_at, updated_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		ch.ID, ch.UserID, ch.Title, ch.Type, ch.Description, ch.Model, ch.SystemPrompt,
		models.NullString(ch.ProviderConfigID), folder, models.NullString(ch.FolderID),
		tagsJSON, aiMode, now.Format(timeFmt), now.Format(timeFmt),
	)
	if err != nil {
		return fmt.Errorf("CreateFull insert channel: %w", err)
	}

	// Add owner participant
	_, _ = tx.ExecContext(ctx, `
		INSERT INTO channel_participants (id, channel_id, participant_type, participant_id, role)
		VALUES (?, ?, 'user', ?, 'owner')
		ON CONFLICT DO NOTHING`, store.NewID(), ch.ID, ownerUserID)

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

	// Auto-create channel_model if model specified
	if defaultModel != "" {
		_, _ = tx.ExecContext(ctx, `
			INSERT INTO channel_models (id, channel_id, model_id, provider_config_id, is_default)
			VALUES (?, ?, ?, ?, 1)
			ON CONFLICT DO NOTHING`, store.NewID(), 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 = json_patch(COALESCE(settings, '{}'), ?) WHERE id = ?`,
		string(settingsJSON), channelID)
	return err
}

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

func scanChannelListItems(rows *sql.Rows) ([]store.ChannelListItem, error) {
	var result []store.ChannelListItem
	for rows.Next() {
		var item store.ChannelListItem
		var tags, settings string
		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, st(&item.CreatedAtTime), st(&item.UpdatedAtTime),
		)
		if err != nil {
			return nil, err
		}
		item.Tags = ScanArray(tags)
		if item.Tags == nil {
			item.Tags = []string{}
		}
		item.Settings = safeJSONString(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 safeJSONString(s string) json.RawMessage {
	if s == "" || s == "null" {
		return json.RawMessage("{}")
	}
	return json.RawMessage(s)
}