package api

import (
	"context"
	"fmt"
	"regexp"
	"time"

	"github.com/alcionai/clues"
	"github.com/jaytaylor/html2text"
	"github.com/microsoftgraph/msgraph-sdk-go/models"
	"github.com/microsoftgraph/msgraph-sdk-go/teams"

	"github.com/alcionai/corso/src/internal/common/ptr"
	"github.com/alcionai/corso/src/internal/common/str"
	"github.com/alcionai/corso/src/internal/m365/graph"
	"github.com/alcionai/corso/src/pkg/backup/details"
	"github.com/alcionai/corso/src/pkg/logger"
)

// ---------------------------------------------------------------------------
// controller
// ---------------------------------------------------------------------------

func (c Client) Channels() Channels {
	return Channels{c}
}

// Channels is an interface-compliant provider of the client.
type Channels struct {
	Client
}

// ---------------------------------------------------------------------------
// containers
// ---------------------------------------------------------------------------

func (c Channels) GetChannel(
	ctx context.Context,
	teamID, containerID string,
) (models.Channelable, error) {
	config := &teams.ItemChannelsChannelItemRequestBuilderGetRequestConfiguration{
		QueryParameters: &teams.ItemChannelsChannelItemRequestBuilderGetQueryParameters{
			Select: idAnd("displayName"),
		},
	}

	resp, err := c.Stable.
		Client().
		Teams().
		ByTeamId(teamID).
		Channels().
		ByChannelId(containerID).
		Get(ctx, config)
	if err != nil {
		return nil, graph.Stack(ctx, err)
	}

	return resp, nil
}

// GetChannelByName fetches a channel by name
func (c Channels) GetChannelByName(
	ctx context.Context,
	teamID, containerName string,
) (models.Channelable, error) {
	ctx = clues.Add(ctx, "channel_name", containerName)

	filter := fmt.Sprintf("displayName eq '%s'", containerName)
	options := &teams.ItemChannelsRequestBuilderGetRequestConfiguration{
		QueryParameters: &teams.ItemChannelsRequestBuilderGetQueryParameters{
			Filter: &filter,
		},
	}

	resp, err := c.Stable.
		Client().
		Teams().
		ByTeamId(teamID).
		Channels().
		Get(ctx, options)
	if err != nil {
		return nil, graph.Stack(ctx, err).WithClues(ctx)
	}

	gv := resp.GetValue()
	if len(gv) == 0 {
		return nil, clues.New("channel not found").WithClues(ctx)
	}

	// We only allow the api to match one channel with the provided name.
	// If we match multiples, we'll eagerly return the first one.
	logger.Ctx(ctx).Debugw("channels matched the name search")

	// Sanity check ID and name
	cal := gv[0]

	if err := checkIDAndName(cal); err != nil {
		return nil, clues.Stack(err).WithClues(ctx)
	}

	return cal, nil
}

// ---------------------------------------------------------------------------
// message
// ---------------------------------------------------------------------------

func (c Channels) GetChannelMessage(
	ctx context.Context,
	teamID, channelID, messageID string,
) (models.ChatMessageable, *details.GroupsInfo, error) {
	message, err := c.Stable.
		Client().
		Teams().
		ByTeamId(teamID).
		Channels().
		ByChannelId(channelID).
		Messages().
		ByChatMessageId(messageID).
		Get(ctx, nil)
	if err != nil {
		return nil, nil, graph.Stack(ctx, err)
	}

	replies, err := c.GetChannelMessageReplies(ctx, teamID, channelID, messageID)
	if err != nil {
		return nil, nil, graph.Wrap(ctx, err, "retrieving message replies")
	}

	message.SetReplies(replies)

	info := channelMessageInfo(message)

	return message, info, nil
}

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

func channelMessageInfo(
	msg models.ChatMessageable,
) *details.GroupsInfo {
	var (
		lastReply   models.ChatMessageable
		lastReplyAt time.Time
		modTime     = ptr.OrNow(msg.GetLastModifiedDateTime())
	)

	replies := msg.GetReplies()

	for _, r := range replies {
		cdt := ptr.Val(r.GetCreatedDateTime())
		if cdt.After(lastReplyAt) {
			lastReply = r
			lastReplyAt = ptr.Val(r.GetCreatedDateTime())
		}
	}

	// if the message hasn't been modified since before the most recent
	// reply, set the modified time to the most recent reply.  This ensures
	// we update the message contents to match changes in replies.
	if modTime.Before(lastReplyAt) {
		modTime = lastReplyAt
	}

	preview, contentLen, err := getChatMessageContentPreview(msg)
	if err != nil {
		preview = "malformed or unparseable html" + preview
	}

	message := details.ChannelMessageInfo{
		AttachmentNames: GetChatMessageAttachmentNames(msg),
		CreatedAt:       ptr.Val(msg.GetCreatedDateTime()),
		Creator:         GetChatMessageFrom(msg),
		Preview:         preview,
		ReplyCount:      len(replies),
		Size:            contentLen,
		Subject:         ptr.Val(msg.GetSubject()),
	}

	var lr details.ChannelMessageInfo

	if lastReply != nil {
		preview, contentLen, err = getChatMessageContentPreview(lastReply)
		if err != nil {
			preview = "malformed or unparseable html: " + preview
		}

		lr = details.ChannelMessageInfo{
			AttachmentNames: GetChatMessageAttachmentNames(lastReply),
			CreatedAt:       ptr.Val(lastReply.GetCreatedDateTime()),
			Creator:         GetChatMessageFrom(lastReply),
			Preview:         preview,
			Size:            contentLen,
		}
	}

	return &details.GroupsInfo{
		ItemType:  details.GroupsChannelMessage,
		Modified:  modTime,
		Message:   message,
		LastReply: lr,
	}
}

// checkIDAndName is a validator that ensures the ID
// and name are populated and not zero valued.
func checkIDAndName(c models.Channelable) error {
	if c == nil {
		return clues.New("nil container")
	}

	id := ptr.Val(c.GetId())
	if len(id) == 0 {
		return clues.New("container missing ID")
	}

	dn := ptr.Val(c.GetDisplayName())
	if len(dn) == 0 {
		return clues.New("container missing display name").With("container_id", id)
	}

	return nil
}

func GetChatMessageFrom(msg models.ChatMessageable) string {
	from := msg.GetFrom()

	switch true {
	case from == nil:
		return ""
	case from.GetApplication() != nil:
		return ptr.Val(from.GetApplication().GetDisplayName())
	case from.GetDevice() != nil:
		return ptr.Val(from.GetDevice().GetDisplayName())
	case from.GetUser() != nil:
		return ptr.Val(from.GetUser().GetDisplayName())
	}

	return ""
}

func getChatMessageContentPreview(msg models.ChatMessageable) (string, int64, error) {
	content, origSize, err := stripChatMessageHTML(msg)
	return str.Preview(content, 128), origSize, clues.Stack(err).OrNil()
}

func stripChatMessageHTML(msg models.ChatMessageable) (string, int64, error) {
	var (
		content  string
		origSize int64
	)

	if msg.GetBody() != nil {
		content = ptr.Val(msg.GetBody().GetContent())
	}

	origSize = int64(len(content))

	content = replaceAttachmentMarkup(content, msg.GetAttachments())
	content, err := html2text.FromString(content)

	return content, origSize, clues.Stack(err).OrNil()
}

var attachmentMarkupRE = regexp.MustCompile(`<attachment id=[\\]?"([\d\w-]+)[\\]?"></attachment>`)

// replaces any instance of `<attachment id=\"1693946862569\"></attachment>` with `[attachment:{{name-of-attachment}}]`
// assumes that the attachment ID exists in the attachments slice, otherwise defaults to `[attachment]`.
func replaceAttachmentMarkup(
	content string,
	attachments []models.ChatMessageAttachmentable,
) string {
	attMap := map[string]string{}

	for _, att := range attachments {
		attMap[ptr.Val(att.GetId())] = ptr.Val(att.GetName())
	}

	replacer := func(sub string) string {
		sm := attachmentMarkupRE.FindStringSubmatch(sub)

		if len(sm) > 1 {
			name, ok := attMap[sm[1]]
			if !ok {
				return "[attachment]"
			}

			return fmt.Sprintf("[attachment:%s]", name)
		}

		return "[attachment]"
	}

	return attachmentMarkupRE.ReplaceAllStringFunc(content, replacer)
}

func GetChatMessageAttachmentNames(msg models.ChatMessageable) []string {
	names := make([]string, 0, len(msg.GetAttachments()))

	for _, a := range msg.GetAttachments() {
		if name := ptr.Val(a.GetName()); len(name) > 0 {
			names = append(names, name)
		}
	}

	return names
}