package server

import (
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"

	"github.com/gorilla/mux"
	"golang.org/x/crypto/bcrypt"

	"git.riou.xyz/jriou/coller/internal"
)

type APIErrorResponse struct {
	Message string `json:"message"`
}

func (e APIErrorResponse) 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 apiError(level int, w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	// Wrap error for logging
	if err != nil {
		err = fmt.Errorf("%v: %w", topLevelErr, err)
	} else {
		err = topLevelErr
	}
	logger.Error(fmt.Sprintf("%v", err))

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(level)
	fmt.Fprint(w, APIErrorResponse{
		Message: fmt.Sprintf("%v", topLevelErr),
	}.ToJSON())
}

func APIError(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	apiError(http.StatusInternalServerError, w, logger, topLevelErr, err)
}

func APIErrorNotFound(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	apiError(http.StatusNotFound, w, logger, topLevelErr, err)
}

func APIErrorBadRequest(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	apiError(http.StatusBadRequest, w, logger, topLevelErr, err)
}

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

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

func (h *CreateNoteHandler) Name() string {
	return "CreateNoteHandler"
}

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

type CreateNoteResponse struct {
	ID int64 `json:"id"`
}

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

	logger := h.logger.With("handler", h.Name())

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

	var body CreateNotePayload
	err := json.NewDecoder(bodyReader).Decode(&body)
	if err != nil {
		APIError(w, logger, ErrCouldNotDecodePayload, err)
		return
	}

	if !h.allowNoEncryption && !body.Encrypted {
		APIError(w, logger, ErrEncryptionRequired, nil)
		return
	}

	if !h.allowClientEncryptionKey && body.EncryptionKey != "" {
		APIError(w, logger, ErrClientEncryptionKeyNotAllowed, nil)
		return
	}

	content, err := internal.Decode(body.Content)
	if err != nil {
		APIError(w, logger, ErrCouldNotDecodeContent, err)
		return
	}

	password, err := internal.Decode(body.Password)
	if err != nil {
		APIError(w, logger, ErrCouldNotDecodePassword, err)
		return
	}

	note, err := h.db.Create(content, password, body.EncryptionKey, body.Encrypted, body.Expiration, body.DeleteAfterRead, body.Language)
	if err != nil {
		APIError(w, logger, ErrCouldNotCreateNote, 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) Name() string {
	return "GetNoteHandler"
}

func (h *GetNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")

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

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

	logger := h.logger.With("handler", h.Name(), "note_id", id)

	if err != nil {
		APIError(w, logger, ErrCouldNotFindNote, err)
	} else if note == nil {
		APIErrorNotFound(w, logger, ErrNoteDoesNotExist, nil)
	} else if note.PasswordHash != nil {
		APIErrorBadRequest(w, logger, ErrNoteIsPasswordProtected, nil)
	} 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
	maxUploadSize int64
}

type GetProtectedNotePayload struct {
	EncryptionKey string `json:"encryption_key"`
	Password      string `json:"password"`
}

func (h *GetProtectedNoteHandler) Name() string {
	return "GetProtectedNoteHandler"
}

func (h *GetProtectedNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")

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

	logger := h.logger.With("handler", h.Name(), "note_id", id)

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

	var body GetProtectedNotePayload
	err := json.NewDecoder(bodyReader).Decode(&body)
	if err != nil {
		APIError(w, logger, ErrCouldNotDecodePayload, err)
		return
	}

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

	if err != nil {
		APIError(w, logger, ErrCouldNotFindNote, err)
		return
	} else if note == nil {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	if body.EncryptionKey != "" && note.Encrypted {
		note.Content, err = internal.Decrypt(note.Content, body.EncryptionKey)
		if err != nil {
			APIError(w, logger, ErrCouldNotDecryptNote, err)
			return
		}
	}

	password, err := internal.Decode(body.Password)
	if err != nil {
		APIError(w, logger, ErrCouldNotDecodePassword, err)
		return
	}

	if len(note.PasswordHash) > 0 {
		err := bcrypt.CompareHashAndPassword(note.PasswordHash, password)
		if err != nil {
			APIErrorBadRequest(w, logger, ErrInvalidPassword, err)
			return
		}
	}

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

type ClientHandler struct {
	logger        *slog.Logger
	version       string
	baseURL       string
	baseDirectory string
}

func (h *ClientHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.logger.Debug("rendering client redirection")
	vars := mux.Vars(r)
	os := vars["os"]
	arch := vars["arch"]
	clientName := vars["clientName"]

	if !internal.InSlice(supportedOSes, os) || !internal.InSlice(supportedArches, arch) || !internal.InSlice(supportedClients, clientName) {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	// No disclosure of the version running on the server
	if h.version == "" {
		http.Redirect(w, r, fmt.Sprintf("%s/%s/%s-%s-%s", h.baseURL, "latest", clientName, os, arch), http.StatusMovedPermanently)
		return
	}

	if h.baseDirectory != "" {
		// Serve file locally
		// Example: ./releases/1.2.0/coller-linux-amd64
		http.ServeFile(w, r, fmt.Sprintf("%s/%s/%s-%s-%s", h.baseDirectory, h.version, clientName, os, arch))
	} else {
		// Redirect to a download link
		// Example: https://git.riou.xyz/jriou/coller/releases/download/1.2.0/coller-linux-amd64
		http.Redirect(w, r, fmt.Sprintf("%s/%s/%s-%s-%s", h.baseURL, h.version, clientName, os, arch), http.StatusMovedPermanently)
	}
}