package behavior

import (
	"bytes"
	"os"

	"gopkg.in/yaml.v3"
)

// Structural room-ID references in non-room content files.
//
// Rooms carry their room references in typed structs (world.Room.RewriteRoomIDs
// walks those). Content outside data/rooms — courses, modules, triggers, items,
// objects, mobs — carries the same references in YAML that the admin editor
// reads and writes as generic maps. This walker remaps those references by
// field name so a room rename/swap cannot leave a course obstacle, a transport
// destination, or a trigger teleport pointing at the old ID.
//
// It is deliberately key-aware: only the known structural keys are touched, so
// an author's flag value, delay, quantity, or color index that happens to equal
// a room ID is never rewritten. That is the same rule world.Room.RewriteRoomIDs
// applies to typed fields.

// scalarRoomRefKeys are keys whose value is a single room ID.
var scalarRoomRefKeys = map[string]bool{
	"room":        true, // world.ExitDef.Room, behavior.Condition.Room
	"teleport":    true, // behavior.Step.Teleport
	"destination": true, // game.ModDef.Destination
	"on_fail":     true, // game.ObstacleDef.OnFailRoom
	"room_id":     true, // game.ObstacleDef.RoomID
	"start_room":  true, // game.CourseConfig.StartRoom
}

// listRoomRefKeys are keys whose value is a list of room IDs.
var listRoomRefKeys = map[string]bool{
	"wander_rooms":  true, // world.RoomMob/RoomObject.WanderRooms
	"despawn_rooms": true, // behavior.SpawnMobConfig.DespawnRooms
}

// RemapRoomRefs remaps every structural room-ID reference in a decoded YAML
// value per idMap (oldID -> newID), recursing through maps and lists. It
// returns whether anything changed. idMap is assumed to be a bijection.
//
// The value is expected to be the result of yaml.Unmarshal into any (maps and
// slices of any); unknown shapes are ignored.
func RemapRoomRefs(v any, idMap map[int]int) bool {
	if len(idMap) == 0 {
		return false
	}
	return remapRoomRefs(v, idMap)
}

func remapRoomRefs(v any, idMap map[int]int) bool {
	switch node := v.(type) {
	case map[string]any:
		changed := false
		for key, val := range node {
			if scalarRoomRefKeys[key] {
				if n, ok := asInt(val); ok {
					if newID, mapped := idMap[n]; mapped && newID != n {
						node[key] = newID
						changed = true
					}
					continue
				}
			}
			if listRoomRefKeys[key] {
				if list, ok := val.([]any); ok && remapRoomRefList(list, idMap) {
					changed = true
				}
				continue
			}
			if remapRoomRefs(val, idMap) {
				changed = true
			}
		}
		return changed
	case map[any]any:
		// yaml.v3 decodes into map[string]any, but a caller that round-tripped
		// through a different decoder can hand us map[any]any.
		changed := false
		for key, val := range node {
			ks, ok := key.(string)
			if !ok {
				continue
			}
			if scalarRoomRefKeys[ks] {
				if n, ok := asInt(val); ok {
					if newID, mapped := idMap[n]; mapped && newID != n {
						node[key] = newID
						changed = true
					}
					continue
				}
			}
			if listRoomRefKeys[ks] {
				if list, ok := val.([]any); ok && remapRoomRefList(list, idMap) {
					changed = true
				}
				continue
			}
			if remapRoomRefs(val, idMap) {
				changed = true
			}
		}
		return changed
	case []any:
		changed := false
		for _, item := range node {
			if remapRoomRefs(item, idMap) {
				changed = true
			}
		}
		return changed
	default:
		return false
	}
}

func remapRoomRefList(list []any, idMap map[int]int) bool {
	changed := false
	for i, item := range list {
		n, ok := asInt(item)
		if !ok {
			continue
		}
		if newID, mapped := idMap[n]; mapped && newID != n {
			list[i] = newID
			changed = true
		}
	}
	return changed
}

// MarshalYAMLMap encodes a decoded YAML map with the same settings the admin
// editor uses, so a rewritten content file matches what the editor would write
// and cannot drop a key a typed struct does not model.
func MarshalYAMLMap(m map[string]any) ([]byte, error) {
	var buf bytes.Buffer
	enc := yaml.NewEncoder(&buf)
	enc.SetIndent(2)
	if err := enc.Encode(m); err != nil {
		return nil, err
	}
	if err := enc.Close(); err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

// asInt coerces the numeric types a YAML decoder (or a JSON round-trip) can
// produce for an integer field.
func asInt(v any) (int, bool) {
	switch n := v.(type) {
	case int:
		return n, true
	case int8:
		return int(n), true
	case int16:
		return int(n), true
	case int32:
		return int(n), true
	case int64:
		return int(n), true
	case uint:
		return int(n), true
	case uint8:
		return int(n), true
	case uint16:
		return int(n), true
	case uint32:
		return int(n), true
	case uint64:
		return int(n), true
	case float64:
		return int(n), true
	case float32:
		return int(n), true
	default:
		return 0, false
	}
}

// RoomRefContentDirs are the data subdirectories whose files can carry a
// structural room reference outside data/rooms. Directories not listed here
// (help, players) never do, and players are migrated separately by the game.
var RoomRefContentDirs = []string{"courses", "modules", "triggers", "items", "objects", "mobs"}

// RoomRefFileChange is a content file whose room references moved, with its
// original and rewritten content. Callers stage these into a journaled
// transaction (or write them) and record the before/after images for undo.
type RoomRefFileChange struct {
	Path    string
	Old     []byte
	Content []byte
}

// RewriteRoomRefsInDir walks dir and returns every YAML file whose structural
// room references changed under idMap, re-encoded. A file that cannot be read
// or parsed is skipped: one malformed content file must not block a room
// rename, and the startup validator reports it independently. A missing dir is
// not an error (the content family may be absent).
func RewriteRoomRefsInDir(dir string, idMap map[int]int) ([]RoomRefFileChange, error) {
	if len(idMap) == 0 {
		return nil, nil
	}
	var changes []RoomRefFileChange
	err := WalkYAMLDir(dir, func(path, id string, data []byte) error {
		var v any
		if err := yaml.Unmarshal(data, &v); err != nil {
			return nil
		}
		if !RemapRoomRefs(v, idMap) {
			return nil
		}
		m, ok := v.(map[string]any)
		if !ok {
			return nil
		}
		encoded, err := MarshalYAMLMap(m)
		if err != nil {
			return err
		}
		changes = append(changes, RoomRefFileChange{Path: path, Old: data, Content: encoded})
		return nil
	})
	if os.IsNotExist(err) {
		return nil, nil
	}
	return changes, err
}