package pf

import (
	"encoding/json"
	"errors"
	"net/http"
	"strconv"
	"strings"
)

type Server struct {
	App *App
}

type listingPayload struct {
	URL string `json:"url"`
}

type bulkPayload struct {
	URLs []string `json:"urls"`
}

func (s Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	path := s.apiPath(r.URL.Path)
	switch {
	case path == "/healthz":
		writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
	case path == "/":
		writeJSON(w, http.StatusOK, map[string]string{"service": "monitoring-pf", "ui": "portal", "api": "go"})
	case !strings.HasPrefix(path, "/api/v1"):
		writeError(w, http.StatusNotFound, "not found")
	case path == "/api/v1/access/me" && r.Method == http.MethodGet:
		s.accessMe(w, r)
	case path == "/api/v1/summary" && r.Method == http.MethodGet:
		s.summary(w, r)
	case path == "/api/v1/employees":
		s.employees(w, r)
	case strings.HasPrefix(path, "/api/v1/employees/"):
		s.employeeItem(w, r, path)
	case path == "/api/v1/projects":
		s.projects(w, r)
	case strings.HasPrefix(path, "/api/v1/projects/"):
		s.projectItem(w, r, path)
	case strings.HasPrefix(path, "/api/v1/listings/"):
		s.listingItem(w, r, path)
	default:
		writeError(w, http.StatusNotFound, "not found")
	}
}

func (s Server) apiPath(path string) string {
	base := s.App.Cfg.PublicBasePath
	if base != "" && path == base {
		return "/"
	}
	if base != "" && strings.HasPrefix(path, base+"/") {
		return strings.TrimPrefix(path, base)
	}
	return path
}

func (s Server) accessMe(w http.ResponseWriter, r *http.Request) {
	portalID := portalUserID(r)
	emp, err := s.App.CurrentEmployee(r.Context(), portalID, false)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	botUsername := s.App.Cfg.TGBotUsername
	if botUsername == "" {
		if resolved, err := s.App.TG.BotUsername(r.Context()); err == nil {
			botUsername = resolved
		}
	}
	var link *string
	if botUsername != "" && portalID != "" {
		v := "https://t.me/" + botUsername + "?start=" + portalID
		link = &v
	}
	var command *string
	if portalID != "" {
		v := "/start " + portalID
		command = &v
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"is_admin":               isAdmin(r),
		"portal_user_id":         nullablePlain(portalID),
		"telegram_linked":        emp != nil && emp.TGChatID != nil && *emp.TGChatID != "",
		"employee":               emp,
		"telegram_bot_username":  nullablePlain(botUsername),
		"telegram_start_command": command,
		"telegram_start_link":    link,
	})
}

func (s Server) summary(w http.ResponseWriter, r *http.Request) {
	emp, err := s.App.CurrentEmployee(r.Context(), portalUserID(r), false)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if emp != nil && emp.TGChatID == nil {
		emp = nil
	}
	out, err := s.App.Summary(r.Context(), emp)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, out)
}

func (s Server) employees(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		emp, err := s.App.CurrentEmployee(r.Context(), portalUserID(r), false)
		if err != nil {
			writeError(w, http.StatusInternalServerError, err.Error())
			return
		}
		items, err := s.App.ListEmployees(r.Context(), isAdmin(r), emp)
		if err != nil {
			writeError(w, http.StatusInternalServerError, err.Error())
			return
		}
		writeJSON(w, http.StatusOK, items)
	case http.MethodPost:
		if !isAdmin(r) {
			writeError(w, http.StatusNotFound, "not found")
			return
		}
		var payload EmployeePayload
		if !decodeJSON(w, r, &payload) {
			return
		}
		emp, err := s.App.CreateEmployee(r.Context(), payload)
		if err != nil {
			writeError(w, http.StatusBadRequest, err.Error())
			return
		}
		writeJSON(w, http.StatusCreated, emp)
	default:
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
	}
}

func (s Server) employeeItem(w http.ResponseWriter, r *http.Request, path string) {
	id, ok := pathID(w, strings.TrimPrefix(path, "/api/v1/employees/"))
	if !ok {
		return
	}
	if !isAdmin(r) {
		writeError(w, http.StatusNotFound, "not found")
		return
	}
	switch r.Method {
	case http.MethodPatch:
		var payload EmployeePayload
		if !decodeJSON(w, r, &payload) {
			return
		}
		emp, err := s.App.UpdateEmployee(r.Context(), id, payload)
		if err != nil {
			status := http.StatusBadRequest
			if errors.Is(err, ErrNotFound) {
				status = http.StatusNotFound
			}
			writeError(w, status, err.Error())
			return
		}
		writeJSON(w, http.StatusOK, emp)
	case http.MethodDelete:
		err := s.App.DeleteEmployee(r.Context(), id)
		if err != nil {
			status := http.StatusBadRequest
			if errors.Is(err, ErrNotFound) {
				status = http.StatusNotFound
			}
			writeError(w, status, err.Error())
			return
		}
		w.WriteHeader(http.StatusNoContent)
	default:
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
	}
}

func (s Server) projects(w http.ResponseWriter, r *http.Request) {
	emp, ok := s.requireEmployee(w, r)
	if !ok {
		return
	}
	switch r.Method {
	case http.MethodGet:
		items, err := s.App.ListProjects(r.Context(), emp.ID)
		if err != nil {
			writeError(w, http.StatusInternalServerError, err.Error())
			return
		}
		writeJSON(w, http.StatusOK, items)
	case http.MethodPost:
		var payload ProjectPayload
		if !decodeJSON(w, r, &payload) {
			return
		}
		project, err := s.App.CreateProject(r.Context(), emp.ID, payload)
		if err != nil {
			writeError(w, http.StatusBadRequest, err.Error())
			return
		}
		writeJSON(w, http.StatusCreated, project)
	default:
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
	}
}

func (s Server) projectItem(w http.ResponseWriter, r *http.Request, path string) {
	emp, ok := s.requireEmployee(w, r)
	if !ok {
		return
	}
	rest := strings.TrimPrefix(path, "/api/v1/projects/")
	parts := strings.Split(strings.Trim(rest, "/"), "/")
	if len(parts) == 0 {
		writeError(w, http.StatusNotFound, "not found")
		return
	}
	projectID, ok := pathID(w, parts[0])
	if !ok {
		return
	}
	if len(parts) == 1 {
		s.projectCRUD(w, r, emp.ID, projectID)
		return
	}
	switch {
	case len(parts) == 2 && parts[1] == "check" && r.Method == http.MethodPost:
		if _, err := s.App.ProjectByID(r.Context(), emp.ID, projectID, false); err != nil {
			writeError(w, http.StatusNotFound, "project not found")
			return
		}
		changes, err := s.App.Worker.CheckProject(r.Context(), projectID)
		if err != nil {
			writeError(w, http.StatusBadRequest, err.Error())
			return
		}
		writeJSON(w, http.StatusOK, map[string]int{"changes": changes})
	case len(parts) == 2 && parts[1] == "suggest" && r.Method == http.MethodGet:
		if _, err := s.App.ProjectByID(r.Context(), emp.ID, projectID, false); err != nil {
			writeError(w, http.StatusNotFound, "project not found")
			return
		}
		out, err := s.App.Worker.Suggest(r.Context(), projectID)
		if err != nil {
			writeError(w, http.StatusBadRequest, err.Error())
			return
		}
		writeJSON(w, http.StatusOK, out)
	case len(parts) == 2 && parts[1] == "listings" && r.Method == http.MethodPost:
		s.addListing(w, r, emp.ID, projectID)
	case len(parts) == 3 && parts[1] == "listings" && parts[2] == "bulk" && r.Method == http.MethodPost:
		s.addListings(w, r, emp.ID, projectID)
	default:
		writeError(w, http.StatusNotFound, "not found")
	}
}

func (s Server) projectCRUD(w http.ResponseWriter, r *http.Request, ownerID, projectID int64) {
	switch r.Method {
	case http.MethodGet:
		project, err := s.App.ProjectByID(r.Context(), ownerID, projectID, true)
		if err != nil {
			writeError(w, http.StatusNotFound, "project not found")
			return
		}
		writeJSON(w, http.StatusOK, project)
	case http.MethodPatch:
		var payload ProjectPayload
		if !decodeJSON(w, r, &payload) {
			return
		}
		project, err := s.App.UpdateProject(r.Context(), ownerID, projectID, payload)
		if err != nil {
			status := http.StatusBadRequest
			if errors.Is(err, ErrNotFound) {
				status = http.StatusNotFound
			}
			writeError(w, status, err.Error())
			return
		}
		writeJSON(w, http.StatusOK, project)
	case http.MethodDelete:
		if err := s.App.DeleteProject(r.Context(), ownerID, projectID); err != nil {
			writeError(w, http.StatusNotFound, "project not found")
			return
		}
		w.WriteHeader(http.StatusNoContent)
	default:
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
	}
}

func (s Server) addListing(w http.ResponseWriter, r *http.Request, ownerID, projectID int64) {
	if _, err := s.App.ProjectByID(r.Context(), ownerID, projectID, false); err != nil {
		writeError(w, http.StatusNotFound, "project not found")
		return
	}
	var payload listingPayload
	if !decodeJSON(w, r, &payload) {
		return
	}
	id, err := s.App.Worker.AddListing(r.Context(), projectID, payload.URL)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	listing, err := s.App.ListingByID(r.Context(), id, true)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusCreated, listing)
}

func (s Server) addListings(w http.ResponseWriter, r *http.Request, ownerID, projectID int64) {
	if _, err := s.App.ProjectByID(r.Context(), ownerID, projectID, false); err != nil {
		writeError(w, http.StatusNotFound, "project not found")
		return
	}
	var payload bulkPayload
	if !decodeJSON(w, r, &payload) {
		return
	}
	out, err := s.App.Worker.AddListings(r.Context(), projectID, payload.URLs)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, out)
}

func (s Server) listingItem(w http.ResponseWriter, r *http.Request, path string) {
	emp, ok := s.requireEmployee(w, r)
	if !ok {
		return
	}
	id, ok := pathID(w, strings.TrimPrefix(path, "/api/v1/listings/"))
	if !ok {
		return
	}
	if r.Method != http.MethodDelete {
		writeError(w, http.StatusMethodNotAllowed, "method not allowed")
		return
	}
	if err := s.App.DeleteListing(r.Context(), emp.ID, id); err != nil {
		writeError(w, http.StatusNotFound, "listing not found")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (s Server) requireEmployee(w http.ResponseWriter, r *http.Request) (*Employee, bool) {
	emp, err := s.App.CurrentEmployee(r.Context(), portalUserID(r), true)
	if errors.Is(err, ErrTelegramRequired) {
		writeError(w, http.StatusForbidden, "Сначала авторизуйтесь в Telegram-боте Monitoring PF")
		return nil, false
	}
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return nil, false
	}
	return emp, true
}

func portalUserID(r *http.Request) string {
	return strings.TrimSpace(r.Header.Get("X-User-Id"))
}

func isAdmin(r *http.Request) bool {
	return r.Header.Get("X-User-Is-Admin") == "1"
}

func nullablePlain(value string) *string {
	if strings.TrimSpace(value) == "" {
		return nil
	}
	return &value
}

func pathID(w http.ResponseWriter, value string) (int64, bool) {
	if strings.Contains(value, "/") {
		writeError(w, http.StatusNotFound, "not found")
		return 0, false
	}
	id, err := strconv.ParseInt(value, 10, 64)
	if err != nil || id <= 0 {
		writeError(w, http.StatusNotFound, "not found")
		return 0, false
	}
	return id, true
}

func decodeJSON(w http.ResponseWriter, r *http.Request, out any) bool {
	defer r.Body.Close()
	if err := json.NewDecoder(r.Body).Decode(out); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json")
		return false
	}
	return true
}

func writeJSON(w http.ResponseWriter, status int, value any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

func writeError(w http.ResponseWriter, status int, detail string) {
	writeJSON(w, status, map[string]string{"detail": detail})
}