package store

import (
	"context"
	"crypto/rand"
	"encoding/base32"
	"fmt"
	"strings"
	"time"

	"github.com/loyaly/behavision-server/internal/api"
)

// CreateSite is the row half of opening a shop. The broker half follows it in
// the handler and the provisioner, and both use this so there is one
// definition of what a site is.
func (s *Store) CreateSite(ctx context.Context, clientID, slug, name, tz string) (api.NewSite, error) {
	var out api.NewSite
	if s.secrets == nil {
		return out, ErrNoSecrets
	}
	slug = strings.ToLower(strings.TrimSpace(slug))
	if tz == "" {
		tz = "UTC"
	}
	if _, err := time.LoadLocation(tz); err != nil {
		return out, fmt.Errorf("unknown timezone %q", tz)
	}

	var clientSlug string
	if err := s.pool.QueryRow(ctx, `SELECT slug FROM clients WHERE id = $1::uuid`, clientID).Scan(&clientSlug); err != nil {
		return out, fmt.Errorf("client %s: %w", clientID, err)
	}

	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return out, err
	}
	defer tx.Rollback(ctx) //nolint:errcheck

	// A plain INSERT, not an upsert: the API must not let an owner silently
	// rename an existing shop by re-posting its slug. A duplicate surfaces as
	// 23505 and the handler turns it into 409.
	if err := tx.QueryRow(ctx, `
		INSERT INTO sites (client_id, slug, name, timezone)
		VALUES ($1::uuid, $2, $3, $4)
		RETURNING id::text`, clientID, slug, name, tz).Scan(&out.SiteID); err != nil {
		return out, err
	}
	out.Slug, out.Name, out.Timezone = slug, name, tz
	// The broker username IS the topic namespace: <client>.<site>. The ACL is
	// written against it, so it is derived, never chosen.
	out.Username = clientSlug + "." + slug

	var agentID string
	if err := tx.QueryRow(ctx, `
		INSERT INTO agents (client_id, site_id, mqtt_username)
		VALUES ($1::uuid, $2::uuid, $3)
		RETURNING id::text`, clientID, out.SiteID, out.Username).Scan(&agentID); err != nil {
		return out, fmt.Errorf("create agent: %w", err)
	}

	out.Password, err = randomSecret(24)
	if err != nil {
		return out, err
	}
	// Sealed with the agent id as aad, so a row copied between agents does not
	// decrypt into a working credential.
	sealed, err := s.secrets.SealString(out.Password, agentID)
	if err != nil {
		return out, err
	}
	if _, err := tx.Exec(ctx, `UPDATE agents SET mqtt_password_enc = $2 WHERE id = $1::uuid`, agentID, sealed); err != nil {
		return out, err
	}
	return out, tx.Commit(ctx)
}

// DeleteNewSite removes a shop that was created moments ago and could not be
// registered with the broker. Scoped to the tenant and refused once the shop
// has anything under it: this is compensation for a failed create, not a
// delete-shop feature.
func (s *Store) DeleteNewSite(ctx context.Context, clientID, siteID string) error {
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx) //nolint:errcheck
	var used bool
	if err := tx.QueryRow(ctx, `
		SELECT EXISTS (SELECT 1 FROM visits WHERE site_id = $1::uuid)
		    OR EXISTS (SELECT 1 FROM site_cameras WHERE site_id = $1::uuid)`, siteID).Scan(&used); err != nil {
		return err
	}
	if used {
		return fmt.Errorf("site %s is in use", siteID)
	}
	if _, err := tx.Exec(ctx, `DELETE FROM agents WHERE site_id = $1::uuid AND client_id = $2::uuid`, siteID, clientID); err != nil {
		return err
	}
	if _, err := tx.Exec(ctx, `DELETE FROM sites WHERE id = $1::uuid AND client_id = $2::uuid`, siteID, clientID); err != nil {
		return err
	}
	return tx.Commit(ctx)
}

func randomSecret(n int) (string, error) {
	b := make([]byte, n)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	// base32 without padding: this gets typed, pasted into config files and
	// read down a phone line, and base64's + / = survive none of that.
	return strings.ToLower(base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(b)), nil
}