package main

import (
	"encoding/binary"
	"fmt"
	"net/http"
	"strconv"
	"strings"
	"time"
)

func isMethodAllowed(response *http.ResponseWriter, request *http.Request) bool {
	if request.Method != http.MethodPost {
		http.Error(*response, "POST only", http.StatusMethodNotAllowed)
		return false
	}
	return true
}

func parseRgb(str string) ([3]uint8, error) {
	parts := strings.SplitN(str, ",", 4)
	if len(parts) != 3 {
		return [3]uint8{}, fmt.Errorf("invalid rgb")
	}
	var rgb [3]uint8
	for i, p := range parts {
		n, err := strconv.ParseUint(strings.TrimSpace(p), 10, 8)
		if err != nil {
			return [3]uint8{}, fmt.Errorf("invalid component %d: %w", i, err)
		}
		rgb[i] = uint8(n)
	}
	return rgb, nil
}

func HttpHandleNewUser(response http.ResponseWriter, request *http.Request) {
	if !isMethodAllowed(&response, request) {
		return
	}

	username := request.FormValue("username")
	if len(username) < 4 {
		http.Error(response, "no or short username", http.StatusBadRequest)
		return
	}

	password := request.FormValue("password")
	if len(password) < 8 {
		http.Error(response, "no or short password", http.StatusBadRequest)
		return
	}

	color, err := parseRgb(request.FormValue("color"))
	if err != nil {
		http.Error(response, "bad color", http.StatusBadRequest)
	}

	hashedPassword, err := PasswordHash(password)
	if err != nil {
		http.Error(response, "internal server error", http.StatusInternalServerError)
		return
	}

	newClient := &Client{
		Name:         username,
		PasswordHash: hashedPassword,
		Color:        color,
		CreatedAt:    time.Now(),
	}

	ctx := request.Context()

	err = DbSaveClientWithoutGroups(ctx, newClient)
	if err != nil {
		http.Error(response, "name taken", http.StatusUnauthorized)
		return
	}

	response.WriteHeader(http.StatusAccepted)
	_, err = response.Write([]byte("created"))
	if err != nil {
		http.Error(response, "internal server error", http.StatusInternalServerError)
		return
	}
}

func HttpHandleLogin(response http.ResponseWriter, request *http.Request) {
	if !isMethodAllowed(&response, request) {
		return
	}

	username := request.FormValue("username")
	if len(username) < 4 {
		http.Error(response, "no or short username", http.StatusBadRequest)
		return
	}

	if len(username) < 8 {
		http.Error(response, "no or short password", http.StatusBadRequest)
		return
	}

	var (
		client *Client
		err    error
		ctx    = request.Context()
	)

	client, err = CacheGetClientByName(username)
	if err != nil {
		err := DbSetClientByName(ctx, client)
		if err != nil {
			http.Error(response, "bad login", http.StatusBadRequest)
			return
		}
		CacheSetClient(client)
	}

	token, err := TokenCreate(client.Id)
	if err != nil {
		http.Error(response, "internal server error", http.StatusInternalServerError)
		return
	}

	response.WriteHeader(http.StatusAccepted)
	_, err = response.Write([]byte(token))
	if err != nil {
		CacheDeleteClient(client.Id)
		http.Error(response, "internal server error", http.StatusInternalServerError)
		return
	}
}

func HttpHandleGroupCreate(response http.ResponseWriter, request *http.Request) {
	if !isMethodAllowed(&response, request) {
		return
	}

	token := request.FormValue("token")
	clientId, err := TokenValidateGetId(token)
	if err != nil {
		http.Error(response, "invalid token", http.StatusUnauthorized)
		return
	}

	name := request.FormValue("name")
	if name == "" {
		name = "Best group ever"
	}

	colorString := request.FormValue("color")
	color, err := parseRgb(colorString)
	if err != nil {
		var ok bool
		color, ok = Colors[colorString]
		if !ok {
			color = Colors["default"]
		}
	}

	ctx := request.Context()

	client := Client{Id: clientId}
	cacheClient, err := CacheGetClientById(clientId)
	if err == nil {
		client = *cacheClient
	} else {
		err = DbSetClientById(ctx, &client)
		if err != nil {
			http.Error(response, "internal server error", http.StatusInternalServerError)
			return
		}
	}

	group := Group{
		Name:      name,
		CreatedAt: time.Now(),
		OwnerId:   clientId,
		CreatorId: clientId,
		Color:     color,
	}

	enableClientColors := request.FormValue("enableClientColors")
	if enableClientColors == "1" {
		group.EnableClientColors = true
	}

	err = DbSaveGroupWithoutClients(ctx, &group)
	if err != nil {
		http.Error(response, "internal server error", http.StatusInternalServerError)
		return
	}
	groupIdBytes := make([]byte, 4)
	binary.BigEndian.PutUint32(groupIdBytes, group.Id)

	response.WriteHeader(http.StatusCreated)
	response.Write([]byte(groupIdBytes))
}

func HttpHandleGroupAddClient(response http.ResponseWriter, request *http.Request) {
	if !isMethodAllowed(&response, request) {
		return
	}

	token := request.FormValue("token")
	clientId, err := TokenValidateGetId(token)
	if err != nil {
		http.Error(response, "invalid token", http.StatusUnauthorized)
		return
	}

	affectedGroupId, err := ConvertStringUint32(request.FormValue("groupid"))
	if err != nil {
		http.Error(response, "no such group", http.StatusUnauthorized)
		return
	}

	ctx := request.Context()

	var group Group
	group.Id = affectedGroupId
	groupPtr, err := CacheGetGroup(affectedGroupId)
	if err == nil {
		group = *groupPtr
	} else {
		err = DbSetGroupById(ctx, &group)
		if err != nil {
			http.Error(response, "no such group", http.StatusUnauthorized)
			return
		}
	}

	if group.OwnerId != clientId {
		http.Error(response, "no such group", http.StatusUnauthorized)
		return
	}

	usersToAddString := request.FormValue("users")
	var remainingUsersCount = int(MaxClientsInGroup) - len(group.Clients)
	if remainingUsersCount < 1 {
		http.Error(response, "max users", http.StatusUnauthorized)
		return
	}

	userIdStrings := strings.SplitN(usersToAddString, ",", remainingUsersCount+1)
	if len(userIdStrings) == 0 {
		http.Error(response, "no users to add", http.StatusBadRequest)
		return
	}

	clientIds := make([]uint32, 0, len(userIdStrings))
	for _, s := range userIdStrings {
		id, err := ConvertStringUint32(strings.TrimSpace(s))
		if err != nil {
			continue
		}
		clientIds = append(clientIds, id)
	}
	if len(clientIds) == 0 {
		http.Error(response, "no valid users", http.StatusBadRequest)
		return
	}

	err = DbAddClientsToGroup(ctx, group.Id, clientIds)
	if err != nil {
		http.Error(response, "internal server error", http.StatusInternalServerError)
		return
	}

	response.WriteHeader(http.StatusAccepted)
	_, err = response.Write([]byte("ok"))
	if err != nil {
		http.Error(response, "internal server error", http.StatusInternalServerError)
		return
	}
}