package repository

import (
	"context"
	"encoding/json"
	"errors"
	"time"

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

// AccountTransition is an append-only UserStatus change.
type AccountTransition struct {
	ID         uuid.UUID `json:"id"`
	UserID     uuid.UUID `json:"user_id"`
	FromStatus string    `json:"from_status"`
	ToStatus   string    `json:"to_status"`
	AdminID    uuid.UUID `json:"admin_id"`
	Reason     string    `json:"reason"`
	CreatedAt  time.Time `json:"created_at"`
}

// GetUserStatus returns users.status or empty if missing.
func (r *AdminRepo) GetUserStatus(ctx context.Context, userID uuid.UUID) (string, error) {
	var status string
	err := r.Pool.QueryRow(ctx, `
		SELECT status FROM users WHERE id=$1 AND deleted_at IS NULL`, userID,
	).Scan(&status)
	if errors.Is(err, pgx.ErrNoRows) {
		return "", nil
	}
	return status, err
}

// TransitionUserStatusWithAudit updates status, inserts transition + audit in one tx.
func (r *AdminRepo) TransitionUserStatusWithAudit(
	ctx context.Context,
	adminID, userID uuid.UUID,
	fromStatus, toStatus, reason string,
	meta json.RawMessage,
) error {
	tx, err := r.Pool.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)

	tag, err := tx.Exec(ctx, `
		UPDATE users SET status=$2, updated_at=now()
		WHERE id=$1 AND deleted_at IS NULL AND status=$3`,
		userID, toStatus, fromStatus,
	)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return errString("status conflict")
	}
	if _, err := tx.Exec(ctx, `
		INSERT INTO account_state_transitions(user_id, from_status, to_status, admin_id, reason)
		VALUES ($1,$2,$3,$4,$5)`,
		userID, fromStatus, toStatus, adminID, reason,
	); err != nil {
		return err
	}
	if meta == nil {
		meta = json.RawMessage(`{}`)
	}
	if _, err := tx.Exec(ctx, `
		INSERT INTO admin_audit_logs(admin_id, action, target_type, target_id, meta)
		VALUES ($1,'users.status.transition','user',$2,$3)`,
		adminID, userID.String(), meta,
	); err != nil {
		return err
	}
	return tx.Commit(ctx)
}

// ListStatusTransitions returns newest first.
func (r *AdminRepo) ListStatusTransitions(ctx context.Context, userID uuid.UUID, limit int) ([]AccountTransition, error) {
	if limit <= 0 || limit > 100 {
		limit = 50
	}
	rows, err := r.Pool.Query(ctx, `
		SELECT id, user_id, from_status, to_status, admin_id, reason, created_at
		FROM account_state_transitions
		WHERE user_id=$1
		ORDER BY created_at DESC
		LIMIT $2`, userID, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []AccountTransition
	for rows.Next() {
		var t AccountTransition
		if err := rows.Scan(&t.ID, &t.UserID, &t.FromStatus, &t.ToStatus, &t.AdminID, &t.Reason, &t.CreatedAt); err != nil {
			return nil, err
		}
		out = append(out, t)
	}
	return out, rows.Err()
}