// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See License.txt for license information.

package model

import (
	"crypto/sha1"
	"encoding/hex"
	"encoding/json"
	"io"
	"net/http"
	"sort"
	"strings"
	"unicode/utf8"
)

const (
	CHANNEL_OPEN                   = "O"
	CHANNEL_PRIVATE                = "P"
	CHANNEL_DIRECT                 = "D"
	CHANNEL_GROUP                  = "G"
	CHANNEL_GROUP_MAX_USERS        = 8
	CHANNEL_GROUP_MIN_USERS        = 3
	DEFAULT_CHANNEL                = "town-square"
	CHANNEL_DISPLAY_NAME_MAX_RUNES = 64
	CHANNEL_NAME_MIN_LENGTH        = 2
	CHANNEL_NAME_MAX_LENGTH        = 64
	CHANNEL_NAME_UI_MAX_LENGTH     = 22
	CHANNEL_HEADER_MAX_RUNES       = 1024
	CHANNEL_PURPOSE_MAX_RUNES      = 250
	CHANNEL_CACHE_SIZE             = 25000

	CHANNEL_SORT_BY_USERNAME = "username"
	CHANNEL_SORT_BY_STATUS   = "status"
)

type Channel struct {
	Id            string                 `json:"id"`
	CreateAt      int64                  `json:"create_at"`
	UpdateAt      int64                  `json:"update_at"`
	DeleteAt      int64                  `json:"delete_at"`
	TeamId        string                 `json:"team_id"`
	Type          string                 `json:"type"`
	DisplayName   string                 `json:"display_name"`
	Name          string                 `json:"name"`
	Header        string                 `json:"header"`
	Purpose       string                 `json:"purpose"`
	LastPostAt    int64                  `json:"last_post_at"`
	TotalMsgCount int64                  `json:"total_msg_count"`
	ExtraUpdateAt int64                  `json:"extra_update_at"`
	CreatorId     string                 `json:"creator_id"`
	SchemeId      *string                `json:"scheme_id"`
	Props         map[string]interface{} `json:"props" db:"-"`
}

type ChannelPatch struct {
	DisplayName *string `json:"display_name"`
	Name        *string `json:"name"`
	Header      *string `json:"header"`
	Purpose     *string `json:"purpose"`
}

type ChannelForExport struct {
	Channel
	TeamName   string
	SchemeName *string
}

func (o *Channel) DeepCopy() *Channel {
	copy := *o
	if copy.SchemeId != nil {
		copy.SchemeId = NewString(*o.SchemeId)
	}
	return &copy
}

func (o *Channel) ToJson() string {
	b, _ := json.Marshal(o)
	return string(b)
}

func (o *ChannelPatch) ToJson() string {
	b, _ := json.Marshal(o)
	return string(b)
}

func ChannelFromJson(data io.Reader) *Channel {
	var o *Channel
	json.NewDecoder(data).Decode(&o)
	return o
}

func ChannelPatchFromJson(data io.Reader) *ChannelPatch {
	var o *ChannelPatch
	json.NewDecoder(data).Decode(&o)
	return o
}

func (o *Channel) Etag() string {
	return Etag(o.Id, o.UpdateAt)
}

func (o *Channel) IsValid() *AppError {
	if len(o.Id) != 26 {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.id.app_error", nil, "", http.StatusBadRequest)
	}

	if o.CreateAt == 0 {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.create_at.app_error", nil, "id="+o.Id, http.StatusBadRequest)
	}

	if o.UpdateAt == 0 {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.update_at.app_error", nil, "id="+o.Id, http.StatusBadRequest)
	}

	if utf8.RuneCountInString(o.DisplayName) > CHANNEL_DISPLAY_NAME_MAX_RUNES {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.display_name.app_error", nil, "id="+o.Id, http.StatusBadRequest)
	}

	if !IsValidChannelIdentifier(o.Name) {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.2_or_more.app_error", nil, "id="+o.Id, http.StatusBadRequest)
	}

	if !(o.Type == CHANNEL_OPEN || o.Type == CHANNEL_PRIVATE || o.Type == CHANNEL_DIRECT || o.Type == CHANNEL_GROUP) {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.type.app_error", nil, "id="+o.Id, http.StatusBadRequest)
	}

	if utf8.RuneCountInString(o.Header) > CHANNEL_HEADER_MAX_RUNES {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.header.app_error", nil, "id="+o.Id, http.StatusBadRequest)
	}

	if utf8.RuneCountInString(o.Purpose) > CHANNEL_PURPOSE_MAX_RUNES {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.purpose.app_error", nil, "id="+o.Id, http.StatusBadRequest)
	}

	if len(o.CreatorId) > 26 {
		return NewAppError("Channel.IsValid", "model.channel.is_valid.creator_id.app_error", nil, "", http.StatusBadRequest)
	}

	return nil
}

func (o *Channel) PreSave() {
	if o.Id == "" {
		o.Id = NewId()
	}

	o.CreateAt = GetMillis()
	o.UpdateAt = o.CreateAt
	o.ExtraUpdateAt = 0
}

func (o *Channel) PreUpdate() {
	o.UpdateAt = GetMillis()
}

func (o *Channel) IsGroupOrDirect() bool {
	return o.Type == CHANNEL_DIRECT || o.Type == CHANNEL_GROUP
}

func (o *Channel) Patch(patch *ChannelPatch) {
	if patch.DisplayName != nil {
		o.DisplayName = *patch.DisplayName
	}

	if patch.Name != nil {
		o.Name = *patch.Name
	}

	if patch.Header != nil {
		o.Header = *patch.Header
	}

	if patch.Purpose != nil {
		o.Purpose = *patch.Purpose
	}
}

func (o *Channel) MakeNonNil() {
	if o.Props == nil {
		o.Props = make(map[string]interface{})
	}
}

func (o *Channel) AddProp(key string, value interface{}) {
	o.MakeNonNil()

	o.Props[key] = value
}

func GetDMNameFromIds(userId1, userId2 string) string {
	if userId1 > userId2 {
		return userId2 + "__" + userId1
	} else {
		return userId1 + "__" + userId2
	}
}

func GetGroupDisplayNameFromUsers(users []*User, truncate bool) string {
	usernames := make([]string, len(users))
	for index, user := range users {
		usernames[index] = user.Username
	}

	sort.Strings(usernames)

	name := strings.Join(usernames, ", ")

	if truncate && len(name) > CHANNEL_NAME_MAX_LENGTH {
		name = name[:CHANNEL_NAME_MAX_LENGTH]
	}

	return name
}

func GetGroupNameFromUserIds(userIds []string) string {
	sort.Strings(userIds)

	h := sha1.New()
	for _, id := range userIds {
		io.WriteString(h, id)
	}

	return hex.EncodeToString(h.Sum(nil))
}