package postgres

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

	"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 {
	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)
	}
	// 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, cm.ProviderConfigID, 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 id, channel_id, participant_type, participant_id, role,
			display_name, avatar_url, joined_at
		FROM channel_participants WHERE channel_id = $1 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
		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
}