package admin

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

	"gopkg.in/yaml.v3"
	"thehouseoficarus/internal/behavior"
	"thehouseoficarus/internal/world"
)

// handleRoomInsert models the in-game `room insert <direction>` for the admin
// web GUI. Body: {from, dir, name?}. It creates a new room between `from` (A)
// and the room A's dir exit leads to (B), rewiring A→dir→new, new→dir→B and
// (when B's opposite exit points back at A) B→oppositeDir→new, preserving exit
// properties on both sides. A grid-conflict check (world.InsertGridConflicts)
// rejects inserts that would cause an overlap or twist. Returns the new room.
//
// The write sequence is transactional: the new room is written first, then A,
// then B. If any write after the first fails, the already-applied writes are
// rolled back (new room file deleted, A/B restored) so the on-disk world stays
// consistent and no partial undo entry is pushed. The room index is only
// touched after all writes succeed.
func (s *AdminServer) handleRoomInsert(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, `{"error":"method not allowed"}`, http.StatusMethodNotAllowed)
		return
	}
	var body struct {
		From int    `json:"from"`
		Dir  string `json:"dir"`
		Name string `json:"name"`
	}
	if err := readJSON(r, &body); err != nil || body.From <= 0 || body.Dir == "" {
		writeJSONError(w, "invalid body, need from and dir", http.StatusBadRequest)
		return
	}

	dir := world.ExitDir(strings.ToLower(body.Dir))
	oppositeDir, ok := world.OppositeExit[dir]
	if !ok {
		writeJSONError(w, "invalid direction: "+body.Dir, http.StatusBadRequest)
		return
	}

	aID := body.From
	aRoom, err := s.world.LoadRoom(aID)
	if err != nil {
		writeJSONError(w, fmt.Sprintf("could not load room #%d: %v", aID, err), http.StatusBadRequest)
		return
	}
	aExit, hasExit := aRoom.Exits[dir]
	if !hasExit {
		writeJSONError(w, fmt.Sprintf("room #%d has no %s exit", aID, dir), http.StatusBadRequest)
		return
	}
	bID := aExit.Room
	bRoom, err := s.world.LoadRoom(bID)
	if err != nil {
		writeJSONError(w, fmt.Sprintf("could not load the room to the %s (#%d): %v", dir, bID, err), http.StatusBadRequest)
		return
	}

	aPath, aPathOK := s.world.GetRoomPath(aID)
	if !aPathOK {
		writeJSONError(w, fmt.Sprintf("could not find the file for room #%d", aID), http.StatusInternalServerError)
		return
	}

	newID, subdir, allocErr := s.nextRoomID(aID)
	if allocErr != nil {
		writeJSONError(w, fmt.Sprintf("could not allocate a room id: %v", allocErr), http.StatusInternalServerError)
		return
	}

	name := strings.TrimSpace(body.Name)
	if name == "" {
		name = fmt.Sprintf("Room #%d", newID)
	}

	// Grid-conflict check on a hypothetical post-insert world.
	conflicts := world.InsertGridConflicts(aID, dir, bID, newID, func(id int) (*world.Room, bool) {
		r, err := s.world.LoadRoom(id)
		if err != nil {
			return nil, false
		}
		return r, true
	})
	if len(conflicts) > 0 {
		writeJSONError(w, s.formatGridConflicts(conflicts, "insert"), http.StatusConflict)
		return
	}

	// --- Transactional write sequence -------------------------------------
	newPath := filepath.Join(subdir, strconv.Itoa(newID)+".yaml")
	newRoom := &world.Room{
		Name: name,
		Description: behavior.DescList{
			{Text: "A featureless room."},
		},
		Exits: map[world.ExitDir]world.ExitDef{
			dir:         {Room: bID},
			oppositeDir: {Room: aID},
		},
	}
	newContent, werr := writeYAMLFile(newPath, newRoom)
	if werr != nil {
		writeJSONError(w, "could not write the new room: "+werr.Error(), http.StatusInternalServerError)
		return
	}

	// Rewire A's dir exit to the new room, preserving A's dir-exit props.
	oldA, _ := snapshotFile(aPath)
	aRoom.Exits[dir] = world.RewirePreserving(aExit, newID)
	newA, werr := writeYAMLFile(aPath, aRoom)
	if werr != nil {
		rollbackRemove(newPath)
		writeJSONError(w, "could not update room #"+strconv.Itoa(aID)+": "+werr.Error(), http.StatusInternalServerError)
		return
	}

	// Rewire B's reciprocal exit to the new room, preserving B's own exit
	// props, only when B's opposite exit already points back at A (lenient
	// one-way insertion when it does not).
	var extraFiles []ExtraFile
	bPath, bPathOK := s.world.GetRoomPath(bID)
	var oldB, newB []byte
	bRewired := false
	if bPathOK {
		if bExit, ok := bRoom.Exits[oppositeDir]; ok && bExit.Room == aID {
			oldB, _ = snapshotFile(bPath)
			bRoom.Exits[oppositeDir] = world.RewirePreserving(bExit, newID)
			var berr error
			newB, berr = writeYAMLFile(bPath, bRoom)
			if berr != nil {
				rollbackWrite(aPath, oldA)
				rollbackRemove(newPath)
				writeJSONError(w, "could not update the far room #"+strconv.Itoa(bID)+": "+berr.Error(), http.StatusInternalServerError)
				return
			}
			bRewired = true
		}
	}

	// All writes succeeded: register the new room and record the change.
	s.world.AddRoomPath(newID, newPath)
	extraFiles = append(extraFiles, ExtraFile{
		FilePath:   aPath,
		OldContent: oldA,
		NewContent: newA,
	})
	if bRewired {
		extraFiles = append(extraFiles, ExtraFile{
			FilePath:   bPath,
			OldContent: oldB,
			NewContent: newB,
		})
	}
	s.undoStack.Push(ChangeDesc{
		Description: fmt.Sprintf("insert room %d %s %d (new %d)", aID, dir, bID, newID),
		FilePath:    newPath,
		NewContent:  newContent,
		IsCreate:    true,
		ExtraFiles:  extraFiles,
	})

	writeJSON(w, map[string]any{"room": map[string]any{"id": newID, "name": name}})
}

// handleRoomRemove models the in-game `room remove <direction>` for the admin
// web GUI. Body: {from, dir}. It deletes the room reached via `from`'s dir exit
// (B) and pulls the far room C (B's dir exit's target) back to `from`, rewiring
// from→dir→C and C→oppositeDir→from, preserving exit properties on both sides.
// It fails (400/409) under the same conditions as the in-game command. The GUI
// cannot relocate live players standing in B (a documented limitation of the
// admin/game decoupling — same as the existing Delete Room endpoint); it does
// clear room state and mob instances for B.
//
// The write sequence is transactional: A is rewritten first, then C, then B is
// deleted. If any step after the first fails, the already-applied writes are
// rolled back (A/C restored, B's file left intact) so the on-disk world stays
// consistent and no partial undo entry is pushed. Index/state cleanup runs only
// after the delete succeeds.
func (s *AdminServer) handleRoomRemove(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, `{"error":"method not allowed"}`, http.StatusMethodNotAllowed)
		return
	}
	var body struct {
		From int    `json:"from"`
		Dir  string `json:"dir"`
	}
	if err := readJSON(r, &body); err != nil || body.From <= 0 || body.Dir == "" {
		writeJSONError(w, "invalid body, need from and dir", http.StatusBadRequest)
		return
	}

	dir := world.ExitDir(strings.ToLower(body.Dir))
	oppositeDir, ok := world.OppositeExit[dir]
	if !ok {
		writeJSONError(w, "invalid direction: "+body.Dir, http.StatusBadRequest)
		return
	}

	aID := body.From
	aRoom, err := s.world.LoadRoom(aID)
	if err != nil {
		writeJSONError(w, fmt.Sprintf("could not load room #%d: %v", aID, err), http.StatusBadRequest)
		return
	}
	aExit, hasExit := aRoom.Exits[dir]
	if !hasExit {
		writeJSONError(w, fmt.Sprintf("room #%d has no %s exit", aID, dir), http.StatusBadRequest)
		return
	}
	bID := aExit.Room
	if bID == aID {
		writeJSONError(w, "that exit loops back to the same room", http.StatusBadRequest)
		return
	}
	bRoom, err := s.world.LoadRoom(bID)
	if err != nil {
		writeJSONError(w, fmt.Sprintf("could not load the room to the %s (#%d): %v", dir, bID, err), http.StatusBadRequest)
		return
	}
	bLabel := s.roomLabel(bRoom, bID)

	// Guard 1: B leads back to A via oppositeDir.
	backExit, hasBack := bRoom.Exits[oppositeDir]
	if !hasBack || backExit.Room != aID {
		writeJSONError(w, fmt.Sprintf("cannot remove: %s does not lead back here via %s (not an insert chain)", bLabel, oppositeDir), http.StatusBadRequest)
		return
	}
	// Guard 2: B has a forward dir exit.
	fwdExit, hasFwd := bRoom.Exits[dir]
	if !hasFwd {
		writeJSONError(w, fmt.Sprintf("cannot remove: %s has no room beyond to pull (use Delete Room for a dead-end)", bLabel), http.StatusBadRequest)
		return
	}
	cID := fwdExit.Room
	if cID == bID || cID == aID {
		writeJSONError(w, "cannot remove: the far room is not a distinct room", http.StatusBadRequest)
		return
	}
	// Guard 3: B has exactly two exits.
	if len(bRoom.Exits) != 2 {
		writeJSONError(w, fmt.Sprintf("cannot remove: %s has other exits besides %s and %s", bLabel, oppositeDir, dir), http.StatusBadRequest)
		return
	}
	// Guard 4: C's opposite exit points back at B.
	cRoom, err := s.world.LoadRoom(cID)
	if err != nil {
		writeJSONError(w, fmt.Sprintf("could not load the far room #%d: %v", cID, err), http.StatusBadRequest)
		return
	}
	cOppExit, hasCOpp := cRoom.Exits[oppositeDir]
	if !hasCOpp || cOppExit.Room != bID {
		writeJSONError(w, fmt.Sprintf("cannot remove: the far room #%d does not lead back to %s via %s", cID, bLabel, oppositeDir), http.StatusBadRequest)
		return
	}
	// Guard 5: no extra inbound edges to B.
	if extra := s.countExtraInbound(bID, aID, cID, dir, oppositeDir); extra > 0 {
		writeJSONError(w, fmt.Sprintf("cannot remove: %d other exit(s) point into %s (it was modified since insertion)", extra, bLabel), http.StatusBadRequest)
		return
	}
	// Guard 6: grid-conflict check on a hypothetical post-remove world.
	conflicts := world.RemoveGridConflicts(aID, dir, func(id int) (*world.Room, bool) {
		r, err := s.world.LoadRoom(id)
		if err != nil {
			return nil, false
		}
		return r, true
	})
	if len(conflicts) > 0 {
		writeJSONError(w, s.formatGridConflicts(conflicts, "remove"), http.StatusConflict)
		return
	}

	// --- Transactional write sequence -------------------------------------
	aPath, aPathOK := s.world.GetRoomPath(aID)
	if !aPathOK {
		writeJSONError(w, fmt.Sprintf("could not find the file for room #%d", aID), http.StatusInternalServerError)
		return
	}
	oldA, _ := snapshotFile(aPath)
	aRoom.Exits[dir] = world.RewirePreserving(aExit, cID)
	newA, werr := writeYAMLFile(aPath, aRoom)
	if werr != nil {
		writeJSONError(w, "could not update room #"+strconv.Itoa(aID)+": "+werr.Error(), http.StatusInternalServerError)
		return
	}

	cPath, cPathOK := s.world.GetRoomPath(cID)
	oldC, _ := snapshotFile(cPath)
	var newC []byte
	cRewired := false
	if cPathOK {
		cRoom.Exits[oppositeDir] = world.RewirePreserving(cOppExit, aID)
		var cerr error
		newC, cerr = writeYAMLFile(cPath, cRoom)
		if cerr != nil {
			rollbackWrite(aPath, oldA)
			writeJSONError(w, "could not update the far room #"+strconv.Itoa(cID)+": "+cerr.Error(), http.StatusInternalServerError)
			return
		}
		cRewired = true
	}

	bPath, bPathOK := s.world.GetRoomPath(bID)
	if !bPathOK {
		rollbackWrite(aPath, oldA)
		if cRewired {
			rollbackWrite(cPath, oldC)
		}
		writeJSONError(w, fmt.Sprintf("could not find the file for room #%d", bID), http.StatusInternalServerError)
		return
	}
	oldB, _ := snapshotFile(bPath)
	if rerr := os.Remove(bPath); rerr != nil {
		rollbackWrite(aPath, oldA)
		if cRewired {
			rollbackWrite(cPath, oldC)
		}
		writeJSONError(w, "could not delete room #"+strconv.Itoa(bID)+": "+rerr.Error(), http.StatusInternalServerError)
		return
	}

	// All writes succeeded: rebuild the index and clear B's live state.
	var extraFiles []ExtraFile
	extraFiles = append(extraFiles, ExtraFile{
		FilePath:   aPath,
		OldContent: oldA,
		NewContent: newA,
	})
	if cRewired {
		extraFiles = append(extraFiles, ExtraFile{
			FilePath:   cPath,
			OldContent: oldC,
			NewContent: newC,
		})
	}
	s.world.RebuildRoomIndex(s.dataDir)
	s.world.ClearRoomState(bID)
	if s.mobStore != nil {
		s.mobStore.RemoveMobsInRoom(bID)
	}
	s.undoStack.Push(ChangeDesc{
		Description: fmt.Sprintf("remove room %d %s (pull %d to %d)", bID, dir, cID, aID),
		FilePath:    bPath,
		OldContent:  oldB,
		IsDelete:    true,
		ExtraFiles:  extraFiles,
	})

	writeJSON(w, map[string]any{"ok": true, "removed": bID, "pulled_to": cID})
}

// rollbackWrite restores a file's previous content. Used to undo an already-
// applied write when a later step in a transactional handler fails. Errors are
// logged (not returned) because there is no further recovery available.
func rollbackWrite(path string, oldContent []byte) {
	if oldContent == nil {
		return
	}
	if err := os.WriteFile(path, oldContent, 0644); err != nil {
		fmt.Printf("admin: rollback write %s failed: %v\n", path, err)
	}
}

// rollbackRemove deletes a file that was just created. Used to undo a new-room
// write when a later step in insert fails. Errors are logged (not returned).
func rollbackRemove(path string) {
	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
		fmt.Printf("admin: rollback remove %s failed: %v\n", path, err)
	}
}

// roomLabel returns "#id" or "#id (Name)" for human-readable error messages.
func (s *AdminServer) roomLabel(r *world.Room, id int) string {
	if r != nil && r.Name != "" {
		return fmt.Sprintf("#%d (%s)", id, r.Name)
	}
	return fmt.Sprintf("#%d", id)
}

// formatGridConflicts renders the conflicts returned by Insert/RemoveGridConflicts
// as a single human-readable string, mirroring the in-game command's messages:
// twists become "room #N (Name) would have an ambiguous grid position" and
// overlaps become "would collide with room #N (Name)". mode is "insert" or
// "remove" and selects the leading verb.
func (s *AdminServer) formatGridConflicts(cs []world.GridConflict, mode string) string {
	verb := "insert"
	if mode == "remove" {
		verb = "remove"
	}
	var parts []string
	for _, c := range cs {
		switch c.Kind {
		case "twist":
			r, _ := s.world.LoadRoom(c.Target)
			parts = append(parts, fmt.Sprintf("room %s would have an ambiguous grid position after %s", s.roomLabel(r, c.Target), verb))
		case "overlap":
			tgt, _ := s.world.LoadRoom(c.Target)
			occ, _ := s.world.LoadRoom(c.Occupier)
			parts = append(parts, fmt.Sprintf("%s would cause a grid collision: room %s cannot be placed because room %s is already there", verb, s.roomLabel(tgt, c.Target), s.roomLabel(occ, c.Occupier)))
		}
	}
	if len(parts) == 0 {
		return fmt.Sprintf("cannot %s: it would cause map conflicts", verb)
	}
	return "cannot " + verb + ": " + strings.Join(parts, "; ")
}

// countExtraInbound mirrors Game.countExtraInbound for the admin API: it
// counts 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). 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.
func (s *AdminServer) countExtraInbound(bID, aID, cID int, dir, oppositeDir world.ExitDir) int {
	roomsDir := filepath.Join(s.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 world.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
			}
			if rid == aID && ed == dir {
				continue
			}
			if rid == cID && ed == oppositeDir {
				continue
			}
			extra++
		}
		return nil
	})
	return extra
}