// Package invitestore implements the PostgreSQL-backed adapter for
// `ports.InviteStore`.
//
// PG_PLAN.md §6A migrates Game Lobby Service away from Redis-backed durable
// invite records.
package invitestore

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"strings"
	"time"

	"galaxy/lobby/internal/adapters/postgres/internal/sqlx"
	pgtable "galaxy/lobby/internal/adapters/postgres/jet/lobby/table"
	"galaxy/lobby/internal/domain/common"
	"galaxy/lobby/internal/domain/invite"
	"galaxy/lobby/internal/ports"

	pg "github.com/go-jet/jet/v2/postgres"
)

// Config configures one PostgreSQL-backed invite store instance.
type Config struct {
	DB               *sql.DB
	OperationTimeout time.Duration
}

// Store persists Game Lobby invite records in PostgreSQL.
type Store struct {
	db               *sql.DB
	operationTimeout time.Duration
}

// New constructs one PostgreSQL-backed invite store from cfg.
func New(cfg Config) (*Store, error) {
	if cfg.DB == nil {
		return nil, errors.New("new postgres invite store: db must not be nil")
	}
	if cfg.OperationTimeout <= 0 {
		return nil, errors.New("new postgres invite store: operation timeout must be positive")
	}
	return &Store{
		db:               cfg.DB,
		operationTimeout: cfg.OperationTimeout,
	}, nil
}

// inviteSelectColumns is the canonical SELECT list for the invites table,
// matching scanInvite's column order.
var inviteSelectColumns = pg.ColumnList{
	pgtable.Invites.InviteID,
	pgtable.Invites.GameID,
	pgtable.Invites.InviterUserID,
	pgtable.Invites.InviteeUserID,
	pgtable.Invites.RaceName,
	pgtable.Invites.Status,
	pgtable.Invites.CreatedAt,
	pgtable.Invites.ExpiresAt,
	pgtable.Invites.DecidedAt,
}

// Save persists a new created invite record. Save is create-only; a second
// save against the same invite id maps the unique-violation to
// invite.ErrConflict.
func (store *Store) Save(ctx context.Context, record invite.Invite) error {
	if store == nil || store.db == nil {
		return errors.New("save invite: nil store")
	}
	if err := record.Validate(); err != nil {
		return fmt.Errorf("save invite: %w", err)
	}
	if record.Status != invite.StatusCreated {
		return fmt.Errorf(
			"save invite: status must be %q, got %q",
			invite.StatusCreated, record.Status,
		)
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "save invite", store.operationTimeout)
	if err != nil {
		return err
	}
	defer cancel()

	stmt := pgtable.Invites.INSERT(
		pgtable.Invites.InviteID,
		pgtable.Invites.GameID,
		pgtable.Invites.InviterUserID,
		pgtable.Invites.InviteeUserID,
		pgtable.Invites.RaceName,
		pgtable.Invites.Status,
		pgtable.Invites.CreatedAt,
		pgtable.Invites.ExpiresAt,
		pgtable.Invites.DecidedAt,
	).VALUES(
		record.InviteID.String(),
		record.GameID.String(),
		record.InviterUserID,
		record.InviteeUserID,
		record.RaceName,
		string(record.Status),
		record.CreatedAt.UTC(),
		record.ExpiresAt.UTC(),
		sqlx.NullableTimePtr(record.DecidedAt),
	)

	query, args := stmt.Sql()
	if _, err := store.db.ExecContext(operationCtx, query, args...); err != nil {
		if sqlx.IsUniqueViolation(err) {
			return fmt.Errorf("save invite: %w", invite.ErrConflict)
		}
		return fmt.Errorf("save invite: %w", err)
	}
	return nil
}

// Get returns the record identified by inviteID.
func (store *Store) Get(ctx context.Context, inviteID common.InviteID) (invite.Invite, error) {
	if store == nil || store.db == nil {
		return invite.Invite{}, errors.New("get invite: nil store")
	}
	if err := inviteID.Validate(); err != nil {
		return invite.Invite{}, fmt.Errorf("get invite: %w", err)
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "get invite", store.operationTimeout)
	if err != nil {
		return invite.Invite{}, err
	}
	defer cancel()

	stmt := pg.SELECT(inviteSelectColumns).
		FROM(pgtable.Invites).
		WHERE(pgtable.Invites.InviteID.EQ(pg.String(inviteID.String())))

	query, args := stmt.Sql()
	row := store.db.QueryRowContext(operationCtx, query, args...)
	record, err := scanInvite(row)
	if sqlx.IsNoRows(err) {
		return invite.Invite{}, invite.ErrNotFound
	}
	if err != nil {
		return invite.Invite{}, fmt.Errorf("get invite: %w", err)
	}
	return record, nil
}

// GetByGame returns every invite attached to gameID.
func (store *Store) GetByGame(ctx context.Context, gameID common.GameID) ([]invite.Invite, error) {
	if store == nil || store.db == nil {
		return nil, errors.New("get invites by game: nil store")
	}
	if err := gameID.Validate(); err != nil {
		return nil, fmt.Errorf("get invites by game: %w", err)
	}

	stmt := pg.SELECT(inviteSelectColumns).
		FROM(pgtable.Invites).
		WHERE(pgtable.Invites.GameID.EQ(pg.String(gameID.String()))).
		ORDER_BY(pgtable.Invites.CreatedAt.ASC(), pgtable.Invites.InviteID.ASC())

	return store.queryList(ctx, "get invites by game", stmt)
}

// GetByUser returns every invite addressed to inviteeUserID.
func (store *Store) GetByUser(ctx context.Context, inviteeUserID string) ([]invite.Invite, error) {
	if store == nil || store.db == nil {
		return nil, errors.New("get invites by user: nil store")
	}
	trimmed := strings.TrimSpace(inviteeUserID)
	if trimmed == "" {
		return nil, fmt.Errorf("get invites by user: invitee user id must not be empty")
	}

	stmt := pg.SELECT(inviteSelectColumns).
		FROM(pgtable.Invites).
		WHERE(pgtable.Invites.InviteeUserID.EQ(pg.String(trimmed))).
		ORDER_BY(pgtable.Invites.CreatedAt.ASC(), pgtable.Invites.InviteID.ASC())

	return store.queryList(ctx, "get invites by user", stmt)
}

// GetByInviter returns every invite created by inviterUserID.
func (store *Store) GetByInviter(ctx context.Context, inviterUserID string) ([]invite.Invite, error) {
	if store == nil || store.db == nil {
		return nil, errors.New("get invites by inviter: nil store")
	}
	trimmed := strings.TrimSpace(inviterUserID)
	if trimmed == "" {
		return nil, fmt.Errorf("get invites by inviter: inviter user id must not be empty")
	}

	stmt := pg.SELECT(inviteSelectColumns).
		FROM(pgtable.Invites).
		WHERE(pgtable.Invites.InviterUserID.EQ(pg.String(trimmed))).
		ORDER_BY(pgtable.Invites.CreatedAt.ASC(), pgtable.Invites.InviteID.ASC())

	return store.queryList(ctx, "get invites by inviter", stmt)
}

func (store *Store) queryList(ctx context.Context, operation string, stmt pg.SelectStatement) ([]invite.Invite, error) {
	operationCtx, cancel, err := sqlx.WithTimeout(ctx, operation, store.operationTimeout)
	if err != nil {
		return nil, err
	}
	defer cancel()

	query, args := stmt.Sql()
	rows, err := store.db.QueryContext(operationCtx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("%s: %w", operation, err)
	}
	defer rows.Close()

	records := make([]invite.Invite, 0)
	for rows.Next() {
		record, err := scanInvite(rows)
		if err != nil {
			return nil, fmt.Errorf("%s: scan: %w", operation, err)
		}
		records = append(records, record)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("%s: %w", operation, err)
	}
	if len(records) == 0 {
		return nil, nil
	}
	return records, nil
}

// UpdateStatus applies one status transition with compare-and-swap on the
// current status column. When transitioning to redeemed the row's race_name
// column is replaced with the trimmed input value.
func (store *Store) UpdateStatus(ctx context.Context, input ports.UpdateInviteStatusInput) error {
	if store == nil || store.db == nil {
		return errors.New("update invite status: nil store")
	}
	if err := input.Validate(); err != nil {
		return fmt.Errorf("update invite status: %w", err)
	}
	if err := invite.Transition(input.ExpectedFrom, input.To); err != nil {
		return err
	}

	operationCtx, cancel, err := sqlx.WithTimeout(ctx, "update invite status", store.operationTimeout)
	if err != nil {
		return err
	}
	defer cancel()

	at := input.At.UTC()
	raceName := strings.TrimSpace(input.RaceName)

	// race_name is replaced only when the caller supplies a non-empty value;
	// otherwise the existing value is preserved (CASE WHEN '' THEN race_name).
	raceExpr := pg.CASE().
		WHEN(pg.String(raceName).EQ(pg.String(""))).THEN(pgtable.Invites.RaceName).
		ELSE(pg.String(raceName))

	stmt := pgtable.Invites.UPDATE(
		pgtable.Invites.Status,
		pgtable.Invites.DecidedAt,
		pgtable.Invites.RaceName,
	).SET(
		pg.String(string(input.To)),
		pg.TimestampzT(at),
		raceExpr,
	).WHERE(pg.AND(
		pgtable.Invites.InviteID.EQ(pg.String(input.InviteID.String())),
		pgtable.Invites.Status.EQ(pg.String(string(input.ExpectedFrom))),
	))

	query, args := stmt.Sql()
	result, err := store.db.ExecContext(operationCtx, query, args...)
	if err != nil {
		return fmt.Errorf("update invite status: %w", err)
	}
	affected, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("update invite status: rows affected: %w", err)
	}
	if affected == 0 {
		probe := pg.SELECT(pgtable.Invites.Status).
			FROM(pgtable.Invites).
			WHERE(pgtable.Invites.InviteID.EQ(pg.String(input.InviteID.String())))
		probeQuery, probeArgs := probe.Sql()

		var current string
		row := store.db.QueryRowContext(operationCtx, probeQuery, probeArgs...)
		if err := row.Scan(&current); err != nil {
			if sqlx.IsNoRows(err) {
				return invite.ErrNotFound
			}
			return fmt.Errorf("update invite status: probe: %w", err)
		}
		return fmt.Errorf("update invite status: %w", invite.ErrConflict)
	}
	return nil
}

type rowScanner interface {
	Scan(dest ...any) error
}

func scanInvite(rs rowScanner) (invite.Invite, error) {
	var (
		inviteID      string
		gameID        string
		inviterUserID string
		inviteeUserID string
		raceName      string
		status        string
		createdAt     time.Time
		expiresAt     time.Time
		decidedAt     sql.NullTime
	)
	if err := rs.Scan(
		&inviteID,
		&gameID,
		&inviterUserID,
		&inviteeUserID,
		&raceName,
		&status,
		&createdAt,
		&expiresAt,
		&decidedAt,
	); err != nil {
		return invite.Invite{}, err
	}
	return invite.Invite{
		InviteID:      common.InviteID(inviteID),
		GameID:        common.GameID(gameID),
		InviterUserID: inviterUserID,
		InviteeUserID: inviteeUserID,
		RaceName:      raceName,
		Status:        invite.Status(status),
		CreatedAt:     createdAt.UTC(),
		ExpiresAt:     expiresAt.UTC(),
		DecidedAt:     sqlx.TimePtrFromNullable(decidedAt),
	}, nil
}

// Ensure Store satisfies the ports.InviteStore interface at compile time.
var _ ports.InviteStore = (*Store)(nil)