// Package core holds OpenMail's domain services: inboxes, messages, threads,
// drafts, and the inbound ingest path (parse → thread → store). It is the layer
// the API and MCP server call, and it implements mail.InboundSink so any
// MailBackend can deliver into it.
package core

import (
	"context"
	"errors"

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

	"github.com/karti-ai/openmail/internal/store"
)

// ErrNotFound is returned when a requested resource does not exist.
var ErrNotFound = errors.New("core: not found")

type Service struct {
	pool *pgxpool.Pool
}

func New(st *store.Store) *Service { return &Service{pool: st.Pool} }

// Ping verifies the database connection (used by the health endpoint).
func (s *Service) Ping(ctx context.Context) error { return s.pool.Ping(ctx) }

// EnsureDefaultPod returns the id of the singleton "default" pod, creating it if
// absent. Until DB-backed api_keys carry a pod_id, the API operates within this
// one tenant. Idempotent.
func (s *Service) EnsureDefaultPod(ctx context.Context) (string, error) {
	var id string
	err := s.pool.QueryRow(ctx, `SELECT id::text FROM pods WHERE name = 'default'`).Scan(&id)
	if err == nil {
		return id, nil
	}
	if !errors.Is(err, pgx.ErrNoRows) {
		return "", err
	}
	err = s.pool.QueryRow(ctx,
		`INSERT INTO pods (name) VALUES ('default')
		 ON CONFLICT (name) DO NOTHING
		 RETURNING id::text`).Scan(&id)
	if errors.Is(err, pgx.ErrNoRows) {
		// Lost a race; read the row the other writer created.
		err = s.pool.QueryRow(ctx, `SELECT id::text FROM pods WHERE name = 'default'`).Scan(&id)
	}
	return id, err
}

// nullStr maps an optional string to a value usable as a nullable SQL arg.
func nullStr(s *string) any {
	if s == nil {
		return nil
	}
	return *s
}