package server

import (
	"bytes"
	"errors"
	"fmt"
	"html/template"
	"io"
	"log/slog"
	"net/http"
	"strconv"
	"strings"

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

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

type PageData struct {
	Title                    string
	Version                  string
	Expirations              []int
	Expiration               int
	Languages                []string
	Language                 string
	Err                      error
	URL                      string
	Note                     *Note
	EnablePasswordProtection bool
	EnableUploadFileButton   bool
	AllowClientEncryptionKey bool
	AllowNoEncryption        bool
	AceDirectory             string
	BootstrapDirectory       string
	DisableEditor            bool
	Password                 string // Not stored in the database
}

func WebError(w http.ResponseWriter, pageData PageData, templates *template.Template, templateName string, logger *slog.Logger, topLevelErr error, err error) {
	// Only show the top-level error to users
	pageData.Err = topLevelErr

	// Show full error in the logs
	if err != nil {
		err = fmt.Errorf("%v: %w", topLevelErr, err)
	} else {
		err = pageData.Err
	}
	logger.Error(fmt.Sprintf("%v", err))
	templates.ExecuteTemplate(w, templateName, pageData)
}

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) TemplateName() string {
	return "create"
}

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

func (h *CreateNoteWithFormHandler) WebError(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	WebError(w, h.PageData, h.Templates, h.TemplateName(), logger, topLevelErr, err)
}

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

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

	logger.Debug("parsing multipart form")
	err := r.ParseMultipartForm(h.maxUploadSize)
	if err != nil {
		h.WebError(w, logger, ErrCouldNotParseForm, err)
		return
	}

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

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

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

		logger.Debug("checking file size")
		if handler.Size > h.maxUploadSize {
			h.WebError(w, logger, ErrFileTooLarge, err)
			return
		}

		logger.Debug("checking file content type")
		if !strings.HasPrefix(handler.Header.Get("Content-Type"), "text/") {
			h.WebError(w, logger, ErrTextFileExpected, err)
			return
		}

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

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

	logger.Debug("checking content")
	if content == nil || len(content) == 0 {
		h.WebError(w, logger, ErrEmptyNote, nil)
		return
	}

	logger.Debug("checking inputs")
	password := r.FormValue("password")
	noEncryption := r.FormValue("no-encryption")
	encryptionKey := r.FormValue("encryption-key")
	expiration := r.FormValue("expiration")
	deleteAfterRead := r.FormValue("delete-after-read")
	language := r.FormValue("language")

	if !h.PageData.AllowNoEncryption && noEncryption != "" {
		h.WebError(w, logger, ErrEncryptionRequired, nil)
		return
	}

	if !h.PageData.AllowClientEncryptionKey && encryptionKey != "" {
		h.WebError(w, logger, ErrClientEncryptionKeyNotAllowed, nil)
		return
	}

	if !h.PageData.AllowClientEncryptionKey && encryptionKey == "" && noEncryption == "" {
		logger.Debug("generating encryption key")
		encryptionKey = internal.GenerateChars(encryptionKeyLength)
	}

	logger.Debug("computing expiration")
	var expirationInt int
	if expiration == "Expiration" {
		expirationInt = 0
	} else {
		expirationInt, err = strconv.Atoi(expiration)
		if err != nil {
			h.WebError(w, logger, ErrInvalidExpiration, err)
			return
		}
	}

	logger.Debug("saving note to the database")
	note, err := h.db.Create(content, []byte(password), encryptionKey, encryptionKey != "", expirationInt, deleteAfterRead != "", language)
	if err != nil {
		h.WebError(w, logger, ErrCouldNotCreateNote, err)
		return
	}

	logger.Debug("building note url")

	var scheme = "http://"
	if proto := r.Header.Get("X-Forwarded-Proto"); proto != "" {
		scheme = proto + "://"
	} else if r.TLS != nil {
		scheme = "https://"
	}

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

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

type GetRawWebNoteHandler struct {
	Templates *template.Template
	PageData  PageData
	logger    *slog.Logger
	db        *Database
}

func (h *GetRawWebNoteHandler) TemplateName() string {
	return "unprotectedNote"
}

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

func (h *GetRawWebNoteHandler) WebError(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	WebError(w, h.PageData, h.Templates, h.TemplateName(), logger, topLevelErr, err)
}

func (h *GetRawWebNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.PageData.Err = nil

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

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

	logger.Debug("fetching note from the database")
	note, err := h.db.Get(id)

	if err != nil {
		h.WebError(w, logger, ErrCouldNotFindNote, err)
		return
	}

	if note == nil {
		h.WebError(w, logger, ErrNoteDoesNotExist, err)
		return
	}

	if note.Encrypted || len(note.PasswordHash) > 0 {
		logger.Debug("rendering page")
		h.PageData.Note = note
		h.Templates.ExecuteTemplate(w, h.TemplateName(), h.PageData)
		return
	}

	logger.Debug("returning content")
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.WriteHeader(http.StatusOK)
	fmt.Fprint(w, string(note.Content))
}

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

func (h *GetProtectedRawWebNoteHandler) TemplateName() string {
	return "protectedNote"
}

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

func (h *GetProtectedRawWebNoteHandler) WebError(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	WebError(w, h.PageData, h.Templates, h.TemplateName(), logger, topLevelErr, err)
}

func (h *GetProtectedRawWebNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.PageData.Err = nil

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

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

	logger.Debug("parsing multipart form")
	err := r.ParseMultipartForm(h.maxUploadSize)
	if err != nil {
		h.WebError(w, logger, ErrCouldNotParseForm, err)
		return
	}

	password := r.FormValue("password")
	encryptionKey := r.FormValue("encryption-key")

	logger.Debug("fetching note from the database")
	note, err := h.db.Get(id)

	if err != nil {
		h.WebError(w, logger, ErrCouldNotFindNote, err)
		return
	}

	if note == nil {
		h.WebError(w, logger, ErrNoteDoesNotExist, nil)
		return
	}

	if note.Encrypted {
		if encryptionKey == "" {
			h.WebError(w, logger, ErrEncryptionKeyNotFound, nil)
			return
		}
		logger.Debug("decrypting content")
		note.Content, err = internal.Decrypt(note.Content, encryptionKey)
		if err != nil {
			h.WebError(w, logger, ErrCouldNotDecryptNote, err)
			return
		}
	}

	if len(note.PasswordHash) > 0 {
		logger.Debug("comparing password hashes")
		if err := bcrypt.CompareHashAndPassword(note.PasswordHash, []byte(password)); err != nil {
			h.WebError(w, logger, ErrInvalidPassword, err)
			return
		}
	}

	logger.Debug("returning content")
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.WriteHeader(http.StatusOK)
	fmt.Fprint(w, string(note.Content))
}

type GetWebNoteHandler struct {
	Templates *template.Template
	PageData  PageData
	logger    *slog.Logger
	db        *Database
}

func (h *GetWebNoteHandler) TemplateName() string {
	return "unprotectedNote"
}

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

func (h *GetWebNoteHandler) WebError(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	WebError(w, h.PageData, h.Templates, h.TemplateName(), logger, topLevelErr, err)
}

func (h *GetWebNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.PageData.Err = nil

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

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

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

	if err != nil {
		h.WebError(w, logger, ErrCouldNotFindNote, err)
		return
	}

	if note == nil {
		h.WebError(w, logger, ErrNoteDoesNotExist, nil)
		return
	}

	h.PageData.Note = note

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

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

func (h *GetProtectedWebNoteHandler) TemplateName() string {
	return "protectedNote"
}

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

func (h *GetProtectedWebNoteHandler) WebError(w http.ResponseWriter, logger *slog.Logger, topLevelErr error, err error) {
	WebError(w, h.PageData, h.Templates, h.TemplateName(), logger, topLevelErr, err)
}

func (h *GetProtectedWebNoteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.PageData.Err = nil

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

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

	logger.Debug("parsing multipart form")
	err := r.ParseMultipartForm(h.maxUploadSize)
	if err != nil {
		h.WebError(w, logger, ErrCouldNotParseForm, err)
		return
	}

	password := r.FormValue("password")
	encryptionKey := r.FormValue("encryption-key")

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

	if err != nil {
		h.WebError(w, logger, ErrCouldNotFindNote, err)
		return
	}

	if note == nil {
		h.WebError(w, logger, ErrNoteDoesNotExist, nil)
		return
	}

	if note.Encrypted {
		if encryptionKey == "" {
			h.WebError(w, logger, ErrEncryptionKeyNotFound, nil)
			return
		}
		note.Content, err = internal.Decrypt(note.Content, encryptionKey)
		if err != nil {
			h.WebError(w, logger, ErrCouldNotDecryptNote, err)
			return
		}
	}

	if len(note.PasswordHash) > 0 {
		if err := bcrypt.CompareHashAndPassword(note.PasswordHash, []byte(password)); err != nil {
			h.WebError(w, logger, ErrInvalidPassword, err)
			return
		}
	}

	h.PageData.Password = password
	h.PageData.Note = note

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

type ClientsHandler struct {
	Templates *template.Template
	PageData  PageData
	logger    *slog.Logger
}

func (h *ClientsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.logger.Debug("rendering clients web page")
	h.Templates.ExecuteTemplate(w, "clients", h.PageData)
}