package handlers

import (
	"encoding/json"
	"io"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"github.com/go-chi/chi/v5"
	"xorm.io/xorm"

	"github.com/forgeo/forgebucket/internal/api/middleware"
	"github.com/forgeo/forgebucket/internal/config"
	gitdomain "github.com/forgeo/forgebucket/internal/domain/git"
	"github.com/forgeo/forgebucket/internal/models"
)

// repoResponse enriches a Repository with derived fields the frontend needs.
type repoResponse struct {
	models.Repository
	OwnerName string `json:"ownerName"`
	IsEmpty   bool   `json:"isEmpty"`
	AvatarURL string `json:"avatarUrl"`
	Size      int64  `json:"size"`
}

func avatarPath(repoRoot string, repoID int64) string {
	return filepath.Join(repoRoot, ".avatars", strconv.FormatInt(repoID, 10))
}

func isValidRepoName(name string) bool {
	if len(name) == 0 || len(name) > 100 {
		return false
	}
	for _, c := range name {
		if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
			(c >= '0' && c <= '9') || c == '.' || c == '_' || c == '-') {
			return false
		}
	}
	return true
}

func (h *RepoHandler) withOwnerName(repo *models.Repository) repoResponse {
	var owner models.User
	h.db.ID(repo.OwnerID).Get(&owner)
	gitdomain.SetRepoRoot(h.cfg.RepoRoot)

	avURL := ""
	if _, err := os.Stat(avatarPath(h.cfg.RepoRoot, repo.ID)); err == nil {
		avURL = "/api/v1/repos/" + owner.Username + "/" + repo.Name + "/avatar"
	}

	return repoResponse{
		Repository: *repo,
		AvatarURL:  avURL,
		OwnerName:  owner.Username,
		IsEmpty:    gitdomain.IsEmpty(repo.DiskPath),
	}
}

type RepoHandler struct {
	db  *xorm.Engine
	cfg *config.Config
}

func NewRepoHandler(db *xorm.Engine, cfg *config.Config) *RepoHandler {
	return &RepoHandler{db: db, cfg: cfg}
}

func (h *RepoHandler) List(w http.ResponseWriter, r *http.Request) {
	userID, _ := middleware.UserIDFromContext(r.Context())

	var repos []models.Repository
	if err := h.db.Where("owner_id = ?", userID).Find(&repos); err != nil {
		jsonError(w, "could not list repositories", http.StatusInternalServerError)
		return
	}

	result := make([]repoResponse, len(repos))
	for i := range repos {
		result[i] = h.withOwnerName(&repos[i])
	}
	jsonOK(w, result)
}

func (h *RepoHandler) Create(w http.ResponseWriter, r *http.Request) {
	userID, _ := middleware.UserIDFromContext(r.Context())

	var body struct {
		Name          string `json:"name"`
		Description   string `json:"description"`
		IsPrivate     bool   `json:"isPrivate"`
		DefaultBranch string `json:"defaultBranch"`
		InitReadme    string `json:"initReadme"`    // "none" | "blank" | "tutorial"
		InitGitignore bool   `json:"initGitignore"` // true → add .gitignore
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		jsonError(w, "invalid request body", http.StatusBadRequest)
		return
	}
	if body.Name == "" {
		jsonError(w, "name is required", http.StatusBadRequest)
		return
	}
	branch := body.DefaultBranch
	if branch == "" {
		branch = "main"
	}

	diskPath := filepath.Join(h.cfg.RepoRoot, strconv.FormatInt(userID, 10), body.Name+".git")

	repo := &models.Repository{
		OwnerID:       userID,
		Name:          body.Name,
		Description:   body.Description,
		IsPrivate:     body.IsPrivate,
		DefaultBranch: branch,
		DiskPath:      diskPath,
	}

	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	if err := gitdomain.Init(diskPath); err != nil {
		jsonError(w, "could not initialise git repository", http.StatusInternalServerError)
		return
	}

	// Update bare repo HEAD if branch differs from the Init default (main).
	if branch != "main" {
		gitdomain.SetDefaultBranch(diskPath, branch)
	}

	if _, err := h.db.Insert(repo); err != nil {
		jsonError(w, "repository name already taken", http.StatusConflict)
		return
	}

	// Create initial commit when README or .gitignore was requested.
	wantsReadme := body.InitReadme == "blank" || body.InitReadme == "tutorial"
	if wantsReadme || body.InitGitignore {
		var u models.User
		h.db.ID(userID).Get(&u)
		authorEmail := u.Email
		if authorEmail == "" {
			authorEmail = u.Username + "@forgebucket.local"
		}
		if err := gitdomain.InitWithFiles(diskPath, branch, body.Name, u.Username, authorEmail, wantsReadme, body.InitGitignore); err != nil {
			// Non-fatal: repo is created, just without initial files.
			_ = err
		}
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	json.NewEncoder(w).Encode(h.withOwnerName(repo))
}

func (h *RepoHandler) Import(w http.ResponseWriter, r *http.Request) {
	userID, ok := middleware.UserIDFromContext(r.Context())
	if !ok {
		jsonError(w, "unauthorized", http.StatusUnauthorized)
		return
	}

	var body struct {
		URL         string `json:"url"`
		Name        string `json:"name"`
		Description string `json:"description"`
		IsPrivate   bool   `json:"isPrivate"`
		AuthUser    string `json:"authUser"`
		AuthPass    string `json:"authPass"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		jsonError(w, "invalid request body", http.StatusBadRequest)
		return
	}
	if body.URL == "" || body.Name == "" {
		jsonError(w, "url and name are required", http.StatusBadRequest)
		return
	}

	// Inject credentials into the URL if provided.
	srcURL := body.URL
	if body.AuthUser != "" {
		u, err := url.Parse(body.URL)
		if err != nil {
			jsonError(w, "invalid URL", http.StatusBadRequest)
			return
		}
		u.User = url.UserPassword(body.AuthUser, body.AuthPass)
		srcURL = u.String()
	}

	diskPath := filepath.Join(h.cfg.RepoRoot, strconv.FormatInt(userID, 10), body.Name+".git")

	repo := &models.Repository{
		OwnerID:       userID,
		Name:          body.Name,
		Description:   body.Description,
		IsPrivate:     body.IsPrivate,
		DefaultBranch: "main",
		DiskPath:      diskPath,
	}

	if _, err := h.db.Insert(repo); err != nil {
		jsonError(w, "repository name already taken", http.StatusConflict)
		return
	}

	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	if err := gitdomain.CloneRepo(srcURL, diskPath); err != nil {
		h.db.ID(repo.ID).Delete(&models.Repository{})
		jsonError(w, "import failed: "+err.Error(), http.StatusBadRequest)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	json.NewEncoder(w).Encode(h.withOwnerName(repo))
}

func (h *RepoHandler) Get(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}
	resp := h.withOwnerName(repo)
	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	resp.Size = gitdomain.RepoSize(repo.DiskPath)
	jsonOK(w, resp)
}

func (h *RepoHandler) Tree(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}

	ref := r.URL.Query().Get("ref")
	if ref == "" {
		ref = repo.DefaultBranch
	}
	subPath := r.URL.Query().Get("path")

	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	entries, err := gitdomain.TreeLS(repo.DiskPath, ref, subPath)
	if err != nil {
		jsonError(w, "could not read tree", http.StatusInternalServerError)
		return
	}
	if entries == nil {
		entries = []gitdomain.TreeEntry{}
	}
	jsonOK(w, entries)
}

func (h *RepoHandler) Blob(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}

	ref := r.URL.Query().Get("ref")
	if ref == "" {
		ref = repo.DefaultBranch
	}
	path := r.URL.Query().Get("path")
	if path == "" {
		jsonError(w, "path is required", http.StatusBadRequest)
		return
	}

	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	content, err := gitdomain.BlobCat(repo.DiskPath, ref, path)
	if err != nil {
		jsonError(w, "file not found", http.StatusNotFound)
		return
	}
	jsonOK(w, map[string]string{"content": string(content), "path": path, "ref": ref})
}

func (h *RepoHandler) UpdateBlob(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}

	userID, ok := middleware.UserIDFromContext(r.Context())
	if !ok {
		jsonError(w, "unauthorized", http.StatusUnauthorized)
		return
	}
	var u models.User
	if has, _ := h.db.ID(userID).Get(&u); !has {
		jsonError(w, "user not found", http.StatusUnauthorized)
		return
	}

	var req struct {
		Path    string `json:"path"`
		Content string `json:"content"`
		Message string `json:"message"`
		Branch  string `json:"branch"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonError(w, "invalid body", http.StatusBadRequest)
		return
	}
	if req.Path == "" || req.Message == "" {
		jsonError(w, "path and message are required", http.StatusBadRequest)
		return
	}
	if req.Branch == "" {
		req.Branch = repo.DefaultBranch
	}

	authorEmail := u.Email
	if authorEmail == "" {
		authorEmail = u.Username + "@forgebucket.local"
	}

	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	if err := gitdomain.WriteFile(repo.DiskPath, req.Branch, req.Path, req.Content, u.Username, authorEmail, req.Message); err != nil {
		jsonError(w, "could not save file: "+err.Error(), http.StatusInternalServerError)
		return
	}
	jsonOK(w, map[string]string{"status": "ok"})
}

func (h *RepoHandler) Branches(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}
	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	branches, err := gitdomain.Branches(repo.DiskPath)
	if err != nil {
		jsonError(w, "could not list branches", http.StatusInternalServerError)
		return
	}
	if branches == nil {
		branches = []gitdomain.Branch{}
	}
	jsonOK(w, branches)
}

func (h *RepoHandler) Commits(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}

	ref := r.URL.Query().Get("ref")
	if ref == "" {
		ref = repo.DefaultBranch
	}
	limit := 30
	if l := r.URL.Query().Get("limit"); l != "" {
		if n, err := strconv.Atoi(l); err == nil && n > 0 && n <= 100 {
			limit = n
		}
	}

	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	commits, err := gitdomain.Log(repo.DiskPath, ref, limit)
	if err != nil {
		jsonError(w, "could not read commits", http.StatusInternalServerError)
		return
	}
	if commits == nil {
		commits = []gitdomain.Commit{}
	}
	jsonOK(w, commits)
}

func (h *RepoHandler) Update(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}
	callerID, _ := middleware.UserIDFromContext(r.Context())
	if callerID != repo.OwnerID {
		jsonError(w, "only the owner can update a repository", http.StatusForbidden)
		return
	}

	var body struct {
		Name          *string `json:"name"`
		Description   *string `json:"description"`
		IsPrivate     *bool   `json:"isPrivate"`
		DefaultBranch *string `json:"defaultBranch"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		jsonError(w, "invalid request body", http.StatusBadRequest)
		return
	}

	cols := []string{}

	// Rename: update disk path and DB name atomically.
	if body.Name != nil && *body.Name != "" && *body.Name != repo.Name {
		newName := strings.TrimSpace(*body.Name)
		if !isValidRepoName(newName) {
			jsonError(w, "invalid repository name: use letters, numbers, hyphens, underscores, and dots only", http.StatusBadRequest)
			return
		}
		newDiskPath := filepath.Join(filepath.Dir(repo.DiskPath), newName+".git")
		if _, err := os.Stat(newDiskPath); !os.IsNotExist(err) {
			jsonError(w, "a repository with that name already exists", http.StatusConflict)
			return
		}
		if err := os.Rename(repo.DiskPath, newDiskPath); err != nil {
			jsonError(w, "could not rename repository on disk", http.StatusInternalServerError)
			return
		}
		repo.DiskPath = newDiskPath
		repo.Name = newName
		cols = append(cols, "name", "disk_path")
	}
	if body.Description != nil {
		repo.Description = *body.Description
		cols = append(cols, "description")
	}
	if body.IsPrivate != nil {
		repo.IsPrivate = *body.IsPrivate
		cols = append(cols, "is_private")
	}
	if body.DefaultBranch != nil {
		repo.DefaultBranch = *body.DefaultBranch
		cols = append(cols, "default_branch")
	}

	if len(cols) > 0 {
		if _, err := h.db.ID(repo.ID).Cols(cols...).Update(repo); err != nil {
			jsonError(w, "could not update repository", http.StatusInternalServerError)
			return
		}
	}
	jsonOK(w, h.withOwnerName(repo))
}

// GetAvatar serves the repository avatar image stored on disk.
func (h *RepoHandler) GetAvatar(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}
	data, err := os.ReadFile(avatarPath(h.cfg.RepoRoot, repo.ID))
	if err != nil {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", http.DetectContentType(data))
	w.Header().Set("Cache-Control", "public, max-age=86400")
	w.Write(data)
}

// UploadAvatar accepts a multipart image upload and stores it as the repo avatar.
func (h *RepoHandler) UploadAvatar(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}
	callerID, _ := middleware.UserIDFromContext(r.Context())
	if callerID != repo.OwnerID {
		jsonError(w, "only the owner can change the avatar", http.StatusForbidden)
		return
	}

	r.Body = http.MaxBytesReader(w, r.Body, 5<<20)
	if err := r.ParseMultipartForm(5 << 20); err != nil {
		jsonError(w, "file too large (max 5 MB)", http.StatusBadRequest)
		return
	}
	file, _, err := r.FormFile("avatar")
	if err != nil {
		jsonError(w, "avatar file is required", http.StatusBadRequest)
		return
	}
	defer file.Close()

	// Sniff content type from first 512 bytes, then read the rest.
	sniff := make([]byte, 512)
	n, _ := file.Read(sniff)
	ct := http.DetectContentType(sniff[:n])
	if ct != "image/jpeg" && ct != "image/png" && ct != "image/gif" && ct != "image/webp" {
		jsonError(w, "unsupported image type; use JPEG, PNG, GIF, or WebP", http.StatusBadRequest)
		return
	}
	rest, err := io.ReadAll(file)
	if err != nil {
		jsonError(w, "could not read file", http.StatusInternalServerError)
		return
	}
	data := append(sniff[:n], rest...)

	avatarDir := filepath.Join(h.cfg.RepoRoot, ".avatars")
	if err := os.MkdirAll(avatarDir, 0755); err != nil {
		jsonError(w, "could not create avatar directory", http.StatusInternalServerError)
		return
	}
	if err := os.WriteFile(avatarPath(h.cfg.RepoRoot, repo.ID), data, 0644); err != nil {
		jsonError(w, "could not save avatar", http.StatusInternalServerError)
		return
	}

	var ownerUser models.User
	h.db.ID(repo.OwnerID).Get(&ownerUser)
	jsonOK(w, map[string]string{
		"avatarUrl": "/api/v1/repos/" + ownerUser.Username + "/" + repo.Name + "/avatar",
	})
}

func (h *RepoHandler) Delete(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}

	callerID, _ := middleware.UserIDFromContext(r.Context())
	if callerID != repo.OwnerID {
		jsonError(w, "only the owner can delete a repository", http.StatusForbidden)
		return
	}

	if _, err := h.db.ID(repo.ID).Delete(&models.Repository{}); err != nil {
		jsonError(w, "could not delete repository", http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *RepoHandler) Diff(w http.ResponseWriter, r *http.Request) {
	repo, ok := h.lookupRepo(w, r)
	if !ok {
		return
	}

	base := r.URL.Query().Get("base")
	head := r.URL.Query().Get("head")
	if base == "" || head == "" {
		jsonError(w, "base and head query params are required", http.StatusBadRequest)
		return
	}

	gitdomain.SetRepoRoot(h.cfg.RepoRoot)
	diffs, err := gitdomain.Diff(repo.DiskPath, base, head)
	if err != nil {
		jsonError(w, "could not compute diff", http.StatusInternalServerError)
		return
	}
	if diffs == nil {
		diffs = []gitdomain.FileDiff{}
	}
	jsonOK(w, diffs)
}

// lookupRepo resolves {owner}/{repo} URL params to a DB row, enforcing access.
func (h *RepoHandler) lookupRepo(w http.ResponseWriter, r *http.Request) (*models.Repository, bool) {
	ownerName := chi.URLParam(r, "owner")
	repoName := chi.URLParam(r, "repo")

	var owner models.User
	found, err := h.db.Where("username = ?", ownerName).Get(&owner)
	if err != nil || !found {
		jsonError(w, "repository not found", http.StatusNotFound)
		return nil, false
	}

	var repo models.Repository
	found, err = h.db.Where("owner_id = ? AND name = ?", owner.ID, repoName).Get(&repo)
	if err != nil || !found {
		jsonError(w, "repository not found", http.StatusNotFound)
		return nil, false
	}

	// Private repo: only the owner may access (RBAC will be expanded in Phase 3)
	if repo.IsPrivate {
		callerID, _ := middleware.UserIDFromContext(r.Context())
		if callerID != repo.OwnerID {
			jsonError(w, "repository not found", http.StatusNotFound)
			return nil, false
		}
	}

	return &repo, true
}