package server

import (
	"bytes"
	"embed"
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"io"
	"log/slog"
	"net/http"
	"strconv"

	"git.riou.xyz/jriou/coller/internal"
	"github.com/gorilla/mux"
)

var passwordLength = internal.MIN_PASSWORD_LENGTH

type Server struct {
	logger  *slog.Logger
	db      *Database
	config  *Config
	version string
}

func NewServer(logger *slog.Logger, db *Database, config *Config, version string) (*Server, error) {
	l := logger.With("module", "server")

	return &Server{
		logger:  l,
		db:      db,
		config:  config,
		version: version,
	}, nil
}

func (s *Server) SetIDLength(length int) {
	idLength = length
}

func (s *Server) SetPasswordLength(length int) {
	passwordLength = length
}

type ErrorResponse struct {
	Message string `json:"message"`
	Error   string `json:"error"`
}

func (e ErrorResponse) ToJSON() string {
	b, err := json.Marshal(e)
	if err == nil {
		return string(b)
	}
	return fmt.Sprintf("{\"message\":\"could not serialize response to JSON\", \"error\":\"%v\"}", err)
}

func WriteError(w http.ResponseWriter, message string, err error) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusInternalServerError)
	fmt.Fprint(w, ErrorResponse{
		Message: message,
		Error:   fmt.Sprintf("%v", err),
	}.ToJSON())
}

func HeathHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "OK")
}

type CreateNoteHandler struct {
	logger        *slog.Logger
	db            *Database
	maxUploadSize int64
}

type CreateNotePayload struct {
	Content         string `json:"content"`
	Password        string `json:"password"`
	Encrypted       bool   `json:"encrypted"`
	Expiration      int    `json:"expiration"`
	DeleteAfterRead bool   `json:"delete_after_read"`
}

type CreateNoteResponse struct {
	ID string `json:"id"`
}

func (h *CreateNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")

	bodyReader := http.MaxBytesReader(w, r.Body, h.maxUploadSize)
	defer r.Body.Close()

	var body CreateNotePayload
	err := json.NewDecoder(bodyReader).Decode(&body)
	if err != nil {
		WriteError(w, "could not decode payload to create note", err)
		return
	}

	content, err := internal.Decode(body.Content)

	if err != nil {
		WriteError(w, "could not decode content", err)
		return
	}

	note, err := h.db.Create(content, body.Password, body.Encrypted, body.Expiration, body.DeleteAfterRead)
	if err != nil {
		WriteError(w, "could not create note", err)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(CreateNoteResponse{ID: note.ID})
}

type GetNoteHandler struct {
	logger *slog.Logger
	db     *Database
}

func (h *GetNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain")

	id := mux.Vars(r)["id"]

	note, err := h.db.Get(id)

	if err != nil {
		WriteError(w, "could not get note", err)
	} else if note == nil {
		w.WriteHeader(http.StatusNotFound)
	} else {
		if note.Encrypted {
			w.Header().Set("Content-Type", "application/octet-stream")
		}
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, string(note.Content))
	}
}

type GetProtectedNoteHandler struct {
	logger *slog.Logger
	db     *Database
}

func (h *GetProtectedNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain")

	vars := mux.Vars(r)
	id := vars["id"]
	password := vars["password"]

	note, err := h.db.Get(id)

	if err != nil {
		WriteError(w, "could not get note", err)
		return
	} else if note == nil {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	if password != "" && note.Encrypted {
		note.Content, err = internal.Decrypt(note.Content, password)
		if err != nil {
			WriteError(w, "could not decrypt note", err)
			return
		}
	}

	w.WriteHeader(http.StatusOK)
	fmt.Fprint(w, string(note.Content))
}

type PageData struct {
	Title       string
	Version     string
	Expirations []int
	Err         error
	URL         string
}

type HomeHandler struct {
	Templates *template.Template
	PageData  PageData
}

func (h *HomeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.Templates.ExecuteTemplate(w, "index", h.PageData)
}

type CreateNoteWithFormHandler struct {
	Templates     *template.Template
	PageData      PageData
	logger        *slog.Logger
	db            *Database
	maxUploadSize int64
}

func (h *CreateNoteWithFormHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.PageData.Err = nil
	templateName := "create"

	h.logger.Debug("parsing multipart form")
	err := r.ParseMultipartForm(h.maxUploadSize)
	if err != nil {
		h.PageData.Err = err
		h.Templates.ExecuteTemplate(w, templateName, h.PageData)
		return
	}

	h.logger.Debug("parsing content")
	content := []byte(r.FormValue("content"))

	h.logger.Debug("parsing file")
	file, handler, err := r.FormFile("file")
	if err != nil && !errors.Is(err, http.ErrMissingFile) {
		h.PageData.Err = err
		h.Templates.ExecuteTemplate(w, templateName, h.PageData)
		return
	}

	if !errors.Is(err, http.ErrMissingFile) {
		defer file.Close()

		h.logger.Debug("checking file size")
		if handler.Size > h.maxUploadSize {
			h.PageData.Err = fmt.Errorf("file too large (%d > %d)", handler.Size, h.maxUploadSize)
			h.Templates.ExecuteTemplate(w, templateName, h.PageData)
			return
		}

		h.logger.Debug("checking file content type")
		if handler.Header.Get("Content-Type") != "text/plain" {
			h.PageData.Err = fmt.Errorf("text file expected (got %s)", handler.Header.Get("Content-Type"))
			h.Templates.ExecuteTemplate(w, templateName, h.PageData)
			return
		}

		h.logger.Debug("reading uploaded file")
		var fileContent bytes.Buffer
		n, err := io.Copy(&fileContent, file)
		if err != nil {
			h.PageData.Err = err
			h.Templates.ExecuteTemplate(w, templateName, h.PageData)
			return
		}

		h.logger.Debug("file uploaded", slog.Any("bytes", n))
		if n != 0 {
			content = fileContent.Bytes()
		}
	}

	h.logger.Debug("checking content")
	if content == nil {
		h.PageData.Err = fmt.Errorf("empty note")
		h.Templates.ExecuteTemplate(w, templateName, h.PageData)
		return
	}

	h.logger.Debug("checking inputs")
	noPassword := r.FormValue("no-password")
	password := r.FormValue("password")
	expiration := r.FormValue("expiration")
	deleteAfterRead := r.FormValue("delete-after-read")

	if password == "" && noPassword == "" {
		h.logger.Debug("generating password")
		password = internal.GenerateChars(passwordLength)
	}

	h.logger.Debug("computing expiration")
	var expirationInt int
	if expiration == "Expiration" {
		expirationInt = 0
	} else {
		expirationInt, _ = strconv.Atoi(expiration)
	}

	h.logger.Debug("saving note to the database")
	note, err := h.db.Create(content, password, password != "", expirationInt, deleteAfterRead != "")
	if err != nil {
		h.PageData.Err = err
		h.Templates.ExecuteTemplate(w, templateName, h.PageData)
		return
	}

	h.logger.Debug("building note url")
	var scheme = "http://"
	if r.TLS != nil {
		scheme = "https://"
	}

	h.PageData.URL = fmt.Sprintf("%s%s/%s", scheme, r.Host, note.ID)
	if password != "" {
		h.PageData.URL += "/" + password
	}

	h.logger.Debug("rendering page")
	h.Templates.ExecuteTemplate(w, "create", h.PageData)
}

//go:embed templates/*
var templatesFS embed.FS

func (s *Server) Start() error {
	r := mux.NewRouter().StrictSlash(true)

	// API
	r.HandleFunc("/health", HeathHandler)
	r.Path("/api/note").Handler(&CreateNoteHandler{logger: s.logger, db: s.db, maxUploadSize: s.config.MaxUploadSize}).Methods("POST")
	r.Path("/{id:[a-zA-Z0-9]+}/{password:[a-zA-Z0-9]+}").Handler(&GetProtectedNoteHandler{logger: s.logger, db: s.db}).Methods("GET")
	r.Path("/{id:[a-zA-Z0-9]+}").Handler(&GetNoteHandler{logger: s.logger, db: s.db}).Methods("GET")

	// Web pages
	funcs := template.FuncMap{
		"HumanDuration": internal.HumanDuration,
	}
	p := PageData{
		Title:       s.config.Title,
		Expirations: s.config.Expirations,
	}

	if s.config.ShowVersion {
		p.Version = s.version
	}

	templates, err := template.New("templates").Funcs(funcs).ParseFS(templatesFS, "templates/*.html")
	if err != nil {
		return err
	}
	createNoteWithFormHandler := &CreateNoteWithFormHandler{
		Templates:     templates,
		PageData:      p,
		logger:        s.logger,
		db:            s.db,
		maxUploadSize: s.config.MaxUploadSize,
	}
	r.Path("/create").Handler(createNoteWithFormHandler).Methods("POST")

	r.Path("/").Handler(&HomeHandler{Templates: templates, PageData: p}).Methods("GET")

	addr := fmt.Sprintf("%s:%d", s.config.ListenAddress, s.config.ListenPort)
	return http.ListenAndServe(addr, r)
}