package app

import (
	"context"
	"crypto/rand"
	"crypto/subtle"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"html/template"
	"io"
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/example/glpi-env-controller/internal/backup"
	"github.com/example/glpi-env-controller/internal/dockerctl"
	"github.com/example/glpi-env-controller/internal/envfile"
)

const unchangedSecret = "__ENV_CONTROLLER_UNCHANGED__"

type Server struct {
	cfg      Config
	password string
	csrf     string
	tpl      *template.Template
	docker   dockerctl.Controller
	projects map[string]ProjectConfig
	locks    map[string]*sync.Mutex
	logger   *slog.Logger
}

type pageData struct {
	Title     string
	CSRF      string
	Projects  []projectSummary
	Project   *projectView
	Flash     string
	FlashKind string
	Now       time.Time
}

type projectSummary struct {
	ID, Title               string
	Missing, Extra, Backups int
	Error                   string
}

type fieldView struct {
	Key, Value, Description                          string
	Secret, Missing, Extra, Duplicate, Long, Boolean bool
}

type projectView struct {
	Config        ProjectConfig
	Fields        []fieldView
	Missing       []string
	Extra         []string
	Duplicates    []string
	Backups       []backup.Entry
	Targets       []targetView
	CurrentSHA256 string
}

type targetView struct {
	Target dockerctl.Target
	Status dockerctl.Status
}

func NewServer(cfg Config, password string, htmlTemplate string, logger *slog.Logger) (*Server, error) {
	funcs := template.FuncMap{
		"humanBytes": humanBytes,
		"duration":   func(d time.Duration) string { return d.Round(time.Millisecond).String() },
		"join":       strings.Join,
		"hasAction": func(actions []string, action string) bool {
			for _, a := range actions {
				if a == action {
					return true
				}
			}
			return false
		},
	}
	tpl, err := template.New("page").Funcs(funcs).Parse(htmlTemplate)
	if err != nil {
		return nil, err
	}
	csrfBytes := make([]byte, 32)
	if _, err := rand.Read(csrfBytes); err != nil {
		return nil, err
	}
	if logger == nil {
		logger = slog.Default()
	}
	timeout, _ := time.ParseDuration(cfg.DockerTimeout)
	s := &Server{cfg: cfg, password: password, csrf: base64.RawURLEncoding.EncodeToString(csrfBytes), tpl: tpl, docker: dockerctl.Controller{Timeout: timeout}, projects: map[string]ProjectConfig{}, locks: map[string]*sync.Mutex{}, logger: logger}
	for _, p := range cfg.Projects {
		s.projects[p.ID] = p
		s.locks[p.ID] = &sync.Mutex{}
	}
	return s, nil
}

func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/healthz", s.health)
	mux.HandleFunc("/", s.route)
	return s.securityHeaders(s.basicAuth(mux))
}

func (s *Server) AutoImport(ctx context.Context) {
	if !s.cfg.AutoImportMissing {
		return
	}
	for _, project := range s.cfg.Projects {
		if _, err := s.importMissing(ctx, project, "startup", true, nil); err != nil {
			s.logger.Error("automatic env import failed", "project", project.ID, "error", err)
		}
	}
}

func (s *Server) route(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path == "/" {
		if r.Method != http.MethodGet {
			methodNotAllowed(w)
			return
		}
		s.index(w, r)
		return
	}
	parts := splitPath(r.URL.Path)
	if len(parts) < 2 || parts[0] != "project" {
		http.NotFound(w, r)
		return
	}
	project, ok := s.projects[parts[1]]
	if !ok {
		http.NotFound(w, r)
		return
	}
	if len(parts) == 2 {
		if r.Method != http.MethodGet {
			methodNotAllowed(w)
			return
		}
		s.projectPage(w, r, project, "", "")
		return
	}
	action := parts[2]
	switch action {
	case "save":
		if r.Method != http.MethodPost {
			methodNotAllowed(w)
			return
		}
		s.save(w, r, project)
	case "import":
		if r.Method != http.MethodPost {
			methodNotAllowed(w)
			return
		}
		s.importHandler(w, r, project)
	case "restore":
		if r.Method != http.MethodPost {
			methodNotAllowed(w)
			return
		}
		s.restore(w, r, project)
	case "containers":
		if r.Method != http.MethodPost {
			methodNotAllowed(w)
			return
		}
		s.containers(w, r, project)
	case "reveal":
		if r.Method != http.MethodPost {
			methodNotAllowed(w)
			return
		}
		s.reveal(w, r, project)
	case "backup":
		if r.Method != http.MethodGet || len(parts) != 4 {
			methodNotAllowed(w)
			return
		}
		s.downloadBackup(w, r, project, parts[3])
	default:
		http.NotFound(w, r)
	}
}

func (s *Server) health(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		methodNotAllowed(w)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_, _ = io.WriteString(w, `{"status":"ok"}`)
}

func (s *Server) index(w http.ResponseWriter, r *http.Request) {
	data := pageData{Title: "ENV Controller", CSRF: s.csrf, Now: time.Now()}
	for _, project := range s.cfg.Projects {
		summary := projectSummary{ID: project.ID, Title: project.Title}
		current, example, err := readDocs(project)
		if err != nil {
			summary.Error = err.Error()
		} else {
			missing, extra := envfile.Compare(current, example)
			summary.Missing, summary.Extra = len(missing), len(extra)
		}
		entries, _ := (backup.Store{Dir: project.BackupDir, MaxBackups: s.cfg.MaxBackups}).List()
		summary.Backups = len(entries)
		data.Projects = append(data.Projects, summary)
	}
	s.render(w, data)
}

func (s *Server) projectPage(w http.ResponseWriter, r *http.Request, project ProjectConfig, flash, kind string) {
	view, err := s.loadProjectView(r.Context(), project)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	s.render(w, pageData{Title: project.Title, CSRF: s.csrf, Project: &view, Flash: flash, FlashKind: kind, Now: time.Now()})
}

func (s *Server) loadProjectView(ctx context.Context, project ProjectConfig) (projectView, error) {
	current, example, err := readDocs(project)
	if err != nil {
		return projectView{}, err
	}
	curValues := current.Effective()
	exValues := example.Effective()
	descriptions := envfile.Descriptions(example)
	occ := current.Occurrences()
	missing, extra := envfile.Compare(current, example)
	missingSet := setOf(missing)
	extraSet := setOf(extra)
	var keys []string
	seen := map[string]struct{}{}
	for _, line := range example.Lines {
		if line.Kind == envfile.LineAssignment {
			if _, ok := seen[line.Key]; !ok {
				keys = append(keys, line.Key)
				seen[line.Key] = struct{}{}
			}
		}
	}
	var extraSorted []string
	for key := range curValues {
		if _, ok := seen[key]; !ok {
			extraSorted = append(extraSorted, key)
		}
	}
	sort.Strings(extraSorted)
	keys = append(keys, extraSorted...)
	var fields []fieldView
	for _, key := range keys {
		value, exists := curValues[key]
		if !exists {
			value = exValues[key]
		}
		secret := isSecret(key)
		shown := value
		if secret {
			shown = unchangedSecret
		}
		fields = append(fields, fieldView{Key: key, Value: shown, Description: descriptions[key], Secret: secret, Missing: contains(missingSet, key), Extra: contains(extraSet, key), Duplicate: occ[key] > 1, Long: isLong(key, value), Boolean: isBoolean(exValues[key])})
	}
	var duplicates []string
	for key, count := range occ {
		if count > 1 {
			duplicates = append(duplicates, fmt.Sprintf("%s (%dx)", key, count))
		}
	}
	sort.Strings(duplicates)
	entries, err := (backup.Store{Dir: project.BackupDir, MaxBackups: s.cfg.MaxBackups}).List()
	if err != nil {
		return projectView{}, err
	}
	var targets []targetView
	for _, target := range dockerctl.SortedTargets(project.Targets) {
		targets = append(targets, targetView{Target: target, Status: s.docker.Status(ctx, target)})
	}
	return projectView{Config: project, Fields: fields, Missing: missing, Extra: extra, Duplicates: duplicates, Backups: entries, Targets: targets}, nil
}

func (s *Server) save(w http.ResponseWriter, r *http.Request, project ProjectConfig) {
	if !s.validatePost(w, r) {
		return
	}
	lock := s.locks[project.ID]
	lock.Lock()
	defer lock.Unlock()
	currentData, err := os.ReadFile(project.EnvFile)
	if err != nil {
		s.projectPage(w, r, project, err.Error(), "error")
		return
	}
	current, err := envfile.Parse(currentData)
	if err != nil {
		s.projectPage(w, r, project, err.Error(), "error")
		return
	}
	values := current.Effective()
	for key := range values {
		formKey := "v." + key
		posted, ok := r.Form[formKey]
		if !ok || len(posted) == 0 {
			continue
		}
		value := posted[0]
		if isSecret(key) && value == unchangedSecret {
			continue
		}
		if err := current.Set(key, value); err != nil {
			s.projectPage(w, r, project, err.Error(), "error")
			return
		}
	}
	store := backup.Store{Dir: project.BackupDir, MaxBackups: s.cfg.MaxBackups}
	entry, err := store.Create(project.EnvFile, "edit", s.cfg.Username)
	if err != nil {
		s.projectPage(w, r, project, "Backup fehlgeschlagen: "+err.Error(), "error")
		return
	}
	if err := atomicWrite(project.EnvFile, current.Render()); err != nil {
		s.projectPage(w, r, project, "Schreiben fehlgeschlagen: "+err.Error(), "error")
		return
	}
	message := "Konfiguration gespeichert; Sicherung " + entry.Name + " wurde vorher erstellt."
	message += s.applyFromForm(r.Context(), r, project)
	s.projectPage(w, r, project, message, "success")
}

func (s *Server) importHandler(w http.ResponseWriter, r *http.Request, project ProjectConfig) {
	if !s.validatePost(w, r) {
		return
	}
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	missing, err := s.importMissing(r.Context(), project, s.cfg.Username, true, r)
	if err != nil {
		s.projectPage(w, r, project, err.Error(), "error")
		return
	}
	if len(missing) == 0 {
		s.projectPage(w, r, project, "Keine neuen Einträge in .env.example gefunden.", "info")
		return
	}
	message := fmt.Sprintf("%d neue Einträge importiert: %s.", len(missing), strings.Join(missing, ", "))
	message += s.applyFromForm(r.Context(), r, project)
	s.projectPage(w, r, project, message, "success")
}

func (s *Server) importMissing(_ context.Context, project ProjectConfig, actor string, withBackup bool, _ *http.Request) ([]string, error) {
	lock := s.locks[project.ID]
	lock.Lock()
	defer lock.Unlock()
	current, example, err := readDocs(project)
	if err != nil {
		return nil, err
	}
	missing, _ := envfile.Compare(current, example)
	if len(missing) == 0 {
		return nil, nil
	}
	if withBackup {
		if _, err := (backup.Store{Dir: project.BackupDir, MaxBackups: s.cfg.MaxBackups}).Create(project.EnvFile, "import", actor); err != nil {
			return nil, fmt.Errorf("backup before import: %w", err)
		}
	}
	marker := "# --- Automatisch aus .env.example importiert am " + time.Now().Format(time.RFC3339) + " ---"
	added, err := current.ImportMissing(example, marker)
	if err != nil {
		return nil, err
	}
	if err := atomicWrite(project.EnvFile, current.Render()); err != nil {
		return nil, err
	}
	return added, nil
}

func (s *Server) restore(w http.ResponseWriter, r *http.Request, project ProjectConfig) {
	if !s.validatePost(w, r) {
		return
	}
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	name := r.FormValue("backup")
	if name == "" {
		s.projectPage(w, r, project, "Keine Sicherung ausgewählt.", "error")
		return
	}
	lock := s.locks[project.ID]
	lock.Lock()
	defer lock.Unlock()
	store := backup.Store{Dir: project.BackupDir, MaxBackups: s.cfg.MaxBackups}
	pre, err := store.Create(project.EnvFile, "pre_restore", s.cfg.Username)
	if err != nil {
		s.projectPage(w, r, project, "Sicherung vor Wiederherstellung fehlgeschlagen: "+err.Error(), "error")
		return
	}
	data, err := store.Read(name)
	if err != nil {
		s.projectPage(w, r, project, err.Error(), "error")
		return
	}
	if _, err := envfile.Parse(data); err != nil {
		s.projectPage(w, r, project, "Ungültige Sicherung: "+err.Error(), "error")
		return
	}
	if err := atomicWrite(project.EnvFile, data); err != nil {
		s.projectPage(w, r, project, err.Error(), "error")
		return
	}
	message := "Sicherung " + name + " wiederhergestellt. Der vorherige Stand wurde als " + pre.Name + " gesichert."
	message += s.applyFromForm(r.Context(), r, project)
	s.projectPage(w, r, project, message, "success")
}

func (s *Server) containers(w http.ResponseWriter, r *http.Request, project ProjectConfig) {
	if !s.validatePost(w, r) {
		return
	}
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	message := s.applyFromForm(r.Context(), r, project)
	if message == "" {
		message = " Keine Container ausgewählt."
	}
	s.projectPage(w, r, project, strings.TrimSpace(message), "info")
}

func (s *Server) applyFromForm(ctx context.Context, r *http.Request, project ProjectConfig) string {
	if r.Form == nil {
		_ = r.ParseForm()
	}
	selected := r.Form["target"]
	if len(selected) == 0 {
		return ""
	}
	allow := map[string]dockerctl.Target{}
	for _, target := range project.Targets {
		allow[target.ContainerName] = target
	}
	var results []string
	for _, name := range selected {
		target, ok := allow[name]
		if !ok {
			results = append(results, name+": nicht freigegeben")
			continue
		}
		action := r.FormValue("action." + name)
		if action == "" {
			action = target.DefaultAction
		}
		result := s.docker.Execute(ctx, target, action)
		if result.Success {
			results = append(results, fmt.Sprintf("%s: %s erfolgreich", name, action))
		} else {
			results = append(results, fmt.Sprintf("%s: %s fehlgeschlagen (%s)", name, action, result.Error))
		}
	}
	return " Container-Aktionen: " + strings.Join(results, "; ") + "."
}

func (s *Server) reveal(w http.ResponseWriter, r *http.Request, project ProjectConfig) {
	if !s.validatePost(w, r) {
		return
	}
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	key := r.FormValue("key")
	if !isSecret(key) {
		http.Error(w, "not a secret field", http.StatusBadRequest)
		return
	}
	current, _, err := readDocs(project)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	value, ok := current.Effective()[key]
	if !ok {
		http.Error(w, "unknown key", http.StatusNotFound)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-store")
	_ = json.NewEncoder(w).Encode(map[string]string{"value": value})
}

func (s *Server) downloadBackup(w http.ResponseWriter, r *http.Request, project ProjectConfig, name string) {
	path, err := (backup.Store{Dir: project.BackupDir}).Path(name)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "application/octet-stream")
	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", name))
	w.Header().Set("Cache-Control", "no-store")
	http.ServeFile(w, r, path)
}

func (s *Server) validatePost(w http.ResponseWriter, r *http.Request) bool {
	r.Body = http.MaxBytesReader(w, r.Body, 2<<20)
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return false
	}
	provided := r.FormValue("csrf")
	if subtle.ConstantTimeCompare([]byte(provided), []byte(s.csrf)) != 1 {
		http.Error(w, "invalid CSRF token", http.StatusForbidden)
		return false
	}
	return true
}

func (s *Server) render(w http.ResponseWriter, data pageData) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	if err := s.tpl.ExecuteTemplate(w, "page", data); err != nil {
		s.logger.Error("render page", "error", err)
	}
}

func (s *Server) basicAuth(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/healthz" {
			next.ServeHTTP(w, r)
			return
		}
		user, pass, ok := r.BasicAuth()
		if !ok || subtle.ConstantTimeCompare([]byte(user), []byte(s.cfg.Username)) != 1 || subtle.ConstantTimeCompare([]byte(pass), []byte(s.password)) != 1 {
			w.Header().Set("WWW-Authenticate", `Basic realm="ENV Controller", charset="UTF-8"`)
			http.Error(w, "authentication required", http.StatusUnauthorized)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func (s *Server) securityHeaders(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("Referrer-Policy", "no-referrer")
		w.Header().Set("Permissions-Policy", "camera=(), microphone=(), geolocation=()")
		w.Header().Set("Content-Security-Policy", "default-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline'; connect-src 'self'; frame-ancestors 'none'; base-uri 'none'; form-action 'self'")
		next.ServeHTTP(w, r)
	})
}

func readDocs(project ProjectConfig) (*envfile.Document, *envfile.Document, error) {
	curData, err := os.ReadFile(project.EnvFile)
	if err != nil {
		return nil, nil, fmt.Errorf("read .env: %w", err)
	}
	exData, err := os.ReadFile(project.ExampleFile)
	if err != nil {
		return nil, nil, fmt.Errorf("read .env.example: %w", err)
	}
	cur, err := envfile.Parse(curData)
	if err != nil {
		return nil, nil, err
	}
	ex, err := envfile.Parse(exData)
	if err != nil {
		return nil, nil, err
	}
	return cur, ex, nil
}

func atomicWrite(path string, data []byte) error {
	info, err := os.Stat(path)
	if err != nil {
		return err
	}
	dir := filepath.Dir(path)
	tmp, err := os.CreateTemp(dir, ".env-controller-*")
	if err != nil {
		return err
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName)
	if err := tmp.Chmod(info.Mode().Perm()); err != nil {
		tmp.Close()
		return err
	}
	if err := preserveOwnership(tmpName, info); err != nil {
		tmp.Close()
		return err
	}
	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Sync(); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Close(); err != nil {
		return err
	}
	if err := os.Rename(tmpName, path); err != nil {
		return err
	}
	if d, err := os.Open(dir); err == nil {
		_ = d.Sync()
		_ = d.Close()
	}
	return nil
}

func splitPath(path string) []string {
	var out []string
	for _, p := range strings.Split(strings.Trim(path, "/"), "/") {
		if p != "" {
			out = append(out, p)
		}
	}
	return out
}
func methodNotAllowed(w http.ResponseWriter) {
	http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
}
func setOf(values []string) map[string]struct{} {
	m := map[string]struct{}{}
	for _, v := range values {
		m[v] = struct{}{}
	}
	return m
}
func contains(m map[string]struct{}, k string) bool { _, ok := m[k]; return ok }
func isSecret(key string) bool {
	u := strings.ToUpper(key)
	for _, part := range []string{"PASSWORD", "PASSWD", "SECRET", "TOKEN", "API_KEY", "PRIVATE_KEY", "CREDENTIAL"} {
		if strings.Contains(u, part) {
			return true
		}
	}
	return false
}
func isLong(key, value string) bool {
	return strings.Contains(value, "\n") || len(value) > 100 || strings.HasSuffix(strings.ToUpper(key), "_TEXT")
}
func isBoolean(value string) bool {
	return strings.EqualFold(value, "true") || strings.EqualFold(value, "false")
}
func humanBytes(n int64) string {
	const unit = 1024
	if n < unit {
		return strconv.FormatInt(n, 10) + " B"
	}
	div, exp := int64(unit), 0
	for n >= div*unit && exp < 4 {
		div *= unit
		exp++
	}
	return fmt.Sprintf("%.1f %ciB", float64(n)/float64(div), "KMGTPE"[exp])
}