package world

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"

	"gopkg.in/yaml.v3"
)

// CountExtraInbound returns the number of exits in rooms OTHER than A and C
// that point into B, plus any A/C exits to B other than the expected
// (A→dir→B, C→oppositeDir→B). A nonzero result means B has been modified
// since it was inserted and a remove would silently orphan edges. It walks
// data/rooms and matches \b<id>\b against raw file contents to skip rooms
// that don't mention bID at all, then unmarshals only the matching files.
//
// Shared by the in-game room-remove command and the admin API so the two
// removal paths cannot drift.
func CountExtraInbound(dataDir string, bID, aID, cID int, dir, oppositeDir ExitDir) int {
	roomsDir := filepath.Join(dataDir, "rooms")
	re := regexp.MustCompile(fmt.Sprintf(`\b%d\b`, bID))
	var extra int
	_ = filepath.WalkDir(roomsDir, func(path string, d os.DirEntry, err error) error {
		if err != nil || d.IsDir() || filepath.Ext(path) != ".yaml" {
			return nil
		}
		data, rerr := os.ReadFile(path)
		if rerr != nil {
			return nil
		}
		if !re.MatchString(string(data)) {
			return nil
		}
		idStr := strings.TrimSuffix(filepath.Base(path), ".yaml")
		rid, serr := strconv.Atoi(idStr)
		if serr != nil || rid == bID {
			return nil
		}
		var room Room
		if yerr := yaml.Unmarshal(data, &room); yerr != nil {
			return nil
		}
		if room.Exits == nil {
			return nil
		}
		for ed, exitDef := range room.Exits {
			if exitDef.Room != bID {
				continue
			}
			// Allowed: A→dir→B and C→oppositeDir→B.
			if rid == aID && ed == dir {
				continue
			}
			if rid == cID && ed == oppositeDir {
				continue
			}
			extra++
		}
		return nil
	})
	return extra
}