package onedrive

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"net/http"
	"strings"

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

	"github.com/alcionai/corso/src/internal/common/ptr"
	"github.com/alcionai/corso/src/internal/connector/graph"
	"github.com/alcionai/corso/src/internal/connector/onedrive/metadata"
	"github.com/alcionai/corso/src/pkg/backup/details"
	"github.com/alcionai/corso/src/pkg/logger"
	"github.com/alcionai/corso/src/pkg/services/m365/api"
)

// downloadUrlKeys is used to find the download URL in a DriveItem response.
var downloadURLKeys = []string{
	"@microsoft.graph.downloadUrl",
	"@content.downloadUrl",
}

// sharePointItemReader will return a io.ReadCloser for the specified item
// It crafts this by querying M365 for a download URL for the item
// and using a http client to initialize a reader
// TODO: Add metadata fetching to SharePoint
func sharePointItemReader(
	ctx context.Context,
	client graph.Requester,
	item models.DriveItemable,
) (details.ItemInfo, io.ReadCloser, error) {
	resp, err := downloadItem(ctx, client, item)
	if err != nil {
		return details.ItemInfo{}, nil, clues.Wrap(err, "sharepoint reader")
	}

	dii := details.ItemInfo{
		SharePoint: sharePointItemInfo(item, ptr.Val(item.GetSize())),
	}

	return dii, resp.Body, nil
}

func oneDriveItemMetaReader(
	ctx context.Context,
	service graph.Servicer,
	driveID string,
	item models.DriveItemable,
) (io.ReadCloser, int, error) {
	return baseItemMetaReader(ctx, service, driveID, item)
}

func sharePointItemMetaReader(
	ctx context.Context,
	service graph.Servicer,
	driveID string,
	item models.DriveItemable,
) (io.ReadCloser, int, error) {
	// TODO: include permissions
	return baseItemMetaReader(ctx, service, driveID, item)
}

func baseItemMetaReader(
	ctx context.Context,
	service graph.Servicer,
	driveID string,
	item models.DriveItemable,
) (io.ReadCloser, int, error) {
	var (
		perms []metadata.Permission
		err   error
		meta  = metadata.Metadata{FileName: ptr.Val(item.GetName())}
	)

	if item.GetShared() == nil {
		meta.SharingMode = metadata.SharingModeInherited
	} else {
		meta.SharingMode = metadata.SharingModeCustom
	}

	if meta.SharingMode == metadata.SharingModeCustom {
		perms, err = driveItemPermissionInfo(ctx, service, driveID, ptr.Val(item.GetId()))
		if err != nil {
			return nil, 0, err
		}

		meta.Permissions = perms
	}

	metaJSON, err := json.Marshal(meta)
	if err != nil {
		return nil, 0, clues.Wrap(err, "serializing item metadata").WithClues(ctx)
	}

	return io.NopCloser(bytes.NewReader(metaJSON)), len(metaJSON), nil
}

// oneDriveItemReader will return a io.ReadCloser for the specified item
// It crafts this by querying M365 for a download URL for the item
// and using a http client to initialize a reader
func oneDriveItemReader(
	ctx context.Context,
	client graph.Requester,
	item models.DriveItemable,
) (details.ItemInfo, io.ReadCloser, error) {
	var (
		rc     io.ReadCloser
		isFile = item.GetFile() != nil
	)

	if isFile {
		resp, err := downloadItem(ctx, client, item)
		if err != nil {
			return details.ItemInfo{}, nil, clues.Wrap(err, "onedrive reader")
		}

		rc = resp.Body
	}

	dii := details.ItemInfo{
		OneDrive: oneDriveItemInfo(item, ptr.Val(item.GetSize())),
	}

	return dii, rc, nil
}

func downloadItem(
	ctx context.Context,
	client graph.Requester,
	item models.DriveItemable,
) (*http.Response, error) {
	var url string

	for _, key := range downloadURLKeys {
		tmp, ok := item.GetAdditionalData()[key].(*string)
		if ok {
			url = ptr.Val(tmp)
			break
		}
	}

	if len(url) == 0 {
		return nil, clues.New("extracting file url").With("item_id", ptr.Val(item.GetId()))
	}

	resp, err := client.Request(ctx, http.MethodGet, url, nil, nil)
	if err != nil {
		return nil, err
	}

	if (resp.StatusCode / 100) == 2 {
		return resp, nil
	}

	if graph.IsMalwareResp(ctx, resp) {
		return nil, clues.New("malware detected").Label(graph.LabelsMalware)
	}

	// upstream error checks can compare the status with
	// clues.HasLabel(err, graph.LabelStatus(http.KnownStatusCode))
	cerr := clues.Wrap(clues.New(resp.Status), "non-2xx http response").
		Label(graph.LabelStatus(resp.StatusCode))

	return resp, cerr
}

// oneDriveItemInfo will populate a details.OneDriveInfo struct
// with properties from the drive item.  ItemSize is specified
// separately for restore processes because the local itemable
// doesn't have its size value updated as a side effect of creation,
// and kiota drops any SetSize update.
func oneDriveItemInfo(di models.DriveItemable, itemSize int64) *details.OneDriveInfo {
	var email, driveName, driveID string

	if di.GetCreatedBy() != nil && di.GetCreatedBy().GetUser() != nil {
		// User is sometimes not available when created via some
		// external applications (like backup/restore solutions)
		ed, ok := di.GetCreatedBy().GetUser().GetAdditionalData()["email"]
		if ok {
			email = *ed.(*string)
		}
	}

	if di.GetParentReference() != nil {
		driveID = ptr.Val(di.GetParentReference().GetDriveId())
		driveName = strings.TrimSpace(ptr.Val(di.GetParentReference().GetName()))
	}

	return &details.OneDriveInfo{
		Created:   ptr.Val(di.GetCreatedDateTime()),
		DriveID:   driveID,
		DriveName: driveName,
		ItemName:  ptr.Val(di.GetName()),
		ItemType:  details.OneDriveItem,
		Modified:  ptr.Val(di.GetLastModifiedDateTime()),
		Owner:     email,
		Size:      itemSize,
	}
}

// driveItemPermissionInfo will fetch the permission information
// for a drive item given a drive and item id.
func driveItemPermissionInfo(
	ctx context.Context,
	service graph.Servicer,
	driveID string,
	itemID string,
) ([]metadata.Permission, error) {
	perm, err := api.GetItemPermission(ctx, service, driveID, itemID)
	if err != nil {
		return nil, err
	}

	uperms := filterUserPermissions(ctx, perm.GetValue())

	return uperms, nil
}

func filterUserPermissions(ctx context.Context, perms []models.Permissionable) []metadata.Permission {
	up := []metadata.Permission{}

	for _, p := range perms {
		if p.GetGrantedToV2() == nil {
			// For link shares, we get permissions without a user
			// specified
			continue
		}

		var (
			// Below are the mapping from roles to "Advanced" permissions
			// screen entries:
			//
			// owner - Full Control
			// write - Design | Edit | Contribute (no difference in /permissions api)
			// read  - Read
			// empty - Restricted View
			//
			// helpful docs:
			// https://devblogs.microsoft.com/microsoft365dev/controlling-app-access-on-specific-sharepoint-site-collections/
			roles    = p.GetRoles()
			gv2      = p.GetGrantedToV2()
			entityID string
			gv2t     metadata.GV2Type
		)

		switch true {
		case gv2.GetUser() != nil:
			gv2t = metadata.GV2User
			entityID = ptr.Val(gv2.GetUser().GetId())
		case gv2.GetSiteUser() != nil:
			gv2t = metadata.GV2SiteUser
			entityID = ptr.Val(gv2.GetSiteUser().GetId())
		case gv2.GetGroup() != nil:
			gv2t = metadata.GV2Group
			entityID = ptr.Val(gv2.GetGroup().GetId())
		case gv2.GetSiteGroup() != nil:
			gv2t = metadata.GV2SiteGroup
			entityID = ptr.Val(gv2.GetSiteGroup().GetId())
		case gv2.GetApplication() != nil:
			gv2t = metadata.GV2App
			entityID = ptr.Val(gv2.GetApplication().GetId())
		case gv2.GetDevice() != nil:
			gv2t = metadata.GV2Device
			entityID = ptr.Val(gv2.GetDevice().GetId())
		default:
			logger.Ctx(ctx).Info("untracked permission")
		}

		// Technically GrantedToV2 can also contain devices, but the
		// documentation does not mention about devices in permissions
		if entityID == "" {
			// This should ideally not be hit
			continue
		}

		up = append(up, metadata.Permission{
			ID:         ptr.Val(p.GetId()),
			Roles:      roles,
			EntityID:   entityID,
			EntityType: gv2t,
			Expiration: p.GetExpirationDateTime(),
		})
	}

	return up
}

// sharePointItemInfo will populate a details.SharePointInfo struct
// with properties from the drive item.  ItemSize is specified
// separately for restore processes because the local itemable
// doesn't have its size value updated as a side effect of creation,
// and kiota drops any SetSize update.
// TODO: Update drive name during Issue #2071
func sharePointItemInfo(di models.DriveItemable, itemSize int64) *details.SharePointInfo {
	var driveName, siteID, driveID, weburl, creatorEmail string

	// TODO: we rely on this info for details/restore lookups,
	// so if it's nil we have an issue, and will need an alternative
	// way to source the data.
	if di.GetCreatedBy() != nil && di.GetCreatedBy().GetUser() != nil {
		// User is sometimes not available when created via some
		// external applications (like backup/restore solutions)
		additionalData := di.GetCreatedBy().GetUser().GetAdditionalData()
		ed, ok := additionalData["email"]

		if !ok {
			ed = additionalData["displayName"]
		}

		if ed != nil {
			creatorEmail = *ed.(*string)
		}
	}

	gsi := di.GetSharepointIds()
	if gsi != nil {
		siteID = ptr.Val(gsi.GetSiteId())
		weburl = ptr.Val(gsi.GetSiteUrl())

		if len(weburl) == 0 {
			weburl = constructWebURL(di.GetAdditionalData())
		}
	}

	if di.GetParentReference() != nil {
		driveID = ptr.Val(di.GetParentReference().GetDriveId())
		driveName = strings.TrimSpace(ptr.Val(di.GetParentReference().GetName()))
	}

	return &details.SharePointInfo{
		ItemType:  details.SharePointLibrary,
		ItemName:  ptr.Val(di.GetName()),
		Created:   ptr.Val(di.GetCreatedDateTime()),
		Modified:  ptr.Val(di.GetLastModifiedDateTime()),
		DriveID:   driveID,
		DriveName: driveName,
		Size:      itemSize,
		Owner:     creatorEmail,
		WebURL:    weburl,
		SiteID:    siteID,
	}
}

// driveItemWriter is used to initialize and return an io.Writer to upload data for the specified item
// It does so by creating an upload session and using that URL to initialize an `itemWriter`
// TODO: @vkamra verify if var session is the desired input
func driveItemWriter(
	ctx context.Context,
	gs graph.Servicer,
	driveID, itemID string,
	itemSize int64,
) (io.Writer, error) {
	ctx = clues.Add(ctx, "upload_item_id", itemID)

	r, err := api.PostDriveItem(ctx, gs, driveID, itemID)
	if err != nil {
		return nil, clues.Stack(err)
	}

	iw := graph.NewLargeItemWriter(itemID, ptr.Val(r.GetUploadUrl()), itemSize)

	return iw, nil
}

// constructWebURL helper function for recreating the webURL
// for the originating SharePoint site. Uses additional data map
// from a models.DriveItemable that possesses a downloadURL within the map.
// Returns "" if map nil or key is not present.
func constructWebURL(adtl map[string]any) string {
	var (
		desiredKey = "@microsoft.graph.downloadUrl"
		sep        = `/_layouts`
		url        string
	)

	if adtl == nil {
		return url
	}

	r := adtl[desiredKey]
	point, ok := r.(*string)

	if !ok {
		return url
	}

	value := ptr.Val(point)
	if len(value) == 0 {
		return url
	}

	temp := strings.Split(value, sep)
	url = temp[0]

	return url
}

func setName(orig models.ItemReferenceable, driveName string) models.ItemReferenceable {
	if orig == nil {
		return nil
	}

	orig.SetName(&driveName)

	return orig
}