package repository

import (
	"context"
	"errors"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/yuxingu/digital-psychology/apps/api/internal/model"
)

// AskRepo persists ask threads and messages.
type AskRepo struct {
	Pool *pgxpool.Pool
}

// CreateThread inserts a thread bound to a profile.
func (r *AskRepo) CreateThread(ctx context.Context, userID, profileID uuid.UUID, scene *string) (*model.AskThread, error) {
	t := &model.AskThread{}
	err := r.Pool.QueryRow(ctx, `
		INSERT INTO ask_threads(user_id, profile_id, scene)
		VALUES ($1,$2,$3)
		RETURNING id, user_id, profile_id, scene, created_at`,
		userID, profileID, scene,
	).Scan(&t.ID, &t.UserID, &t.ProfileID, &t.Scene, &t.CreatedAt)
	return t, err
}

// GetThreadForUser loads a thread owned by user.
func (r *AskRepo) GetThreadForUser(ctx context.Context, userID, threadID uuid.UUID) (*model.AskThread, error) {
	t := &model.AskThread{}
	err := r.Pool.QueryRow(ctx, `
		SELECT id, user_id, profile_id, scene, created_at
		FROM ask_threads WHERE id=$1 AND user_id=$2 AND deleted_at IS NULL`,
		threadID, userID,
	).Scan(&t.ID, &t.UserID, &t.ProfileID, &t.Scene, &t.CreatedAt)
	return t, err
}

// ListMessages returns messages in a thread (oldest first).
func (r *AskRepo) ListMessages(ctx context.Context, threadID uuid.UUID) ([]model.AskMessage, error) {
	rows, err := r.Pool.Query(ctx, `
		SELECT id, thread_id, role, content, created_at
		FROM ask_messages WHERE thread_id=$1 AND deleted_at IS NULL
		ORDER BY created_at ASC`, threadID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []model.AskMessage
	for rows.Next() {
		var m model.AskMessage
		if err := rows.Scan(&m.ID, &m.ThreadID, &m.Role, &m.Content, &m.CreatedAt); err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

// InsertMessage stores one message.
func (r *AskRepo) InsertMessage(ctx context.Context, threadID uuid.UUID, role, content string) (*model.AskMessage, error) {
	m := &model.AskMessage{}
	err := r.Pool.QueryRow(ctx, `
		INSERT INTO ask_messages(thread_id, role, content)
		VALUES ($1,$2,$3)
		RETURNING id, thread_id, role, content, created_at`,
		threadID, role, content,
	).Scan(&m.ID, &m.ThreadID, &m.Role, &m.Content, &m.CreatedAt)
	return m, err
}

// CountUserAssistantMessages counts all assistant replies for quota (free tier).
func (r *AskRepo) CountUserAssistantMessages(ctx context.Context, userID uuid.UUID) (int, error) {
	var n int
	err := r.Pool.QueryRow(ctx, `
		SELECT COUNT(*) FROM ask_messages m
		JOIN ask_threads t ON t.id = m.thread_id
		WHERE t.user_id=$1 AND m.role='assistant' AND m.deleted_at IS NULL AND t.deleted_at IS NULL`,
		userID,
	).Scan(&n)
	return n, err
}

// ConsumeMembershipQuota decrements ask_quota_left when membership is active.
// Returns false if no active membership or quota is already 0.
func (r *AskRepo) ConsumeMembershipQuota(ctx context.Context, userID uuid.UUID) (ok bool, left int, err error) {
	err = r.Pool.QueryRow(ctx, `
		UPDATE memberships
		SET ask_quota_left = ask_quota_left - 1, updated_at=now()
		WHERE user_id=$1 AND status='active' AND expires_at > now()
			AND deleted_at IS NULL AND ask_quota_left > 0
		RETURNING ask_quota_left`, userID,
	).Scan(&left)
	if errors.Is(err, pgx.ErrNoRows) {
		return false, 0, nil
	}
	if err != nil {
		return false, 0, err
	}
	return true, left, nil
}