package migration

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"path"
	"strings"

	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/ultisuite/ulti-backend/internal/nextcloud"
)

const maxDriveFileBytes = 25 * 1024 * 1024

type DriveImporter struct {
	db      *pgxpool.Pool
	nc      *nextcloud.Client
	client  *http.Client
	userUPN string
}

func NewDriveImporter(db *pgxpool.Pool, nc *nextcloud.Client) *DriveImporter {
	return &DriveImporter{db: db, nc: nc, client: migrationHTTPClient()}
}

func (d *DriveImporter) WithUserPrincipal(upn string) *DriveImporter {
	d.userUPN = strings.TrimSpace(upn)
	return d
}

func (d *DriveImporter) WithHTTPClient(c *http.Client) *DriveImporter {
	if c != nil {
		d.client = c
	}
	return d
}

func (d *DriveImporter) ImportBatch(ctx context.Context, job *Job, accessToken, provider string, delta bool, update progressUpdater) error {
	if d.nc == nil {
		return fmt.Errorf("nextcloud required for drive migration")
	}
	user, err := resolveMigrationUser(ctx, d.db, job.UserID)
	if err != nil {
		return err
	}
	ncUserID := nextcloud.UserIDFromClaims(user.Email, user.ExternalID)
	if _, err := d.nc.EnsurePrincipal(ctx, user.Email, user.ExternalID, user.Name); err != nil {
		return fmt.Errorf("nextcloud user: %w", err)
	}
	root := fmt.Sprintf("/Migration/%s", provider)
	_ = d.nc.CreateFolder(ctx, ncUserID, root)
	store, err := LoadImportedItemStore(ctx, d.db, job.ID, job.CursorJSON)
	if err != nil {
		return err
	}

	if delta && d.hasDriveDeltaCursor(job, provider) {
		return d.importDriveDelta(ctx, job, accessToken, provider, ncUserID, root, store, update)
	}

	imported, _ := job.StatsJSON["imported"].(float64)
	skipped, _ := job.StatsJSON["skipped"].(float64)
	exported, _ := job.StatsJSON["exported"].(float64)
	batch := 0

	queue := readDriveFolderQueue(job.CursorJSON, provider)
	folderIndex := int(jsonNumber(job.CursorJSON["folderIndex"]))
	if folderIndex >= len(queue) {
		if delta && !d.hasDriveDeltaCursor(job, provider) {
			if err := d.bootstrapDriveDelta(ctx, accessToken, provider, job.CursorJSON); err != nil {
				return err
			}
		}
		job.StatsJSON["imported"] = imported
		job.StatsJSON["skipped"] = skipped
		job.StatsJSON["exported"] = exported
		if delta && d.hasDriveDeltaCursor(job, provider) {
			job.StatsJSON["phase"] = "delta_ready"
		} else {
			job.StatsJSON["phase"] = "imported"
		}
		return update("completed", job.CursorJSON, job.StatsJSON, "")
	}

	current := queue[folderIndex]
	folderItems, nextCursor, subfolders, err := d.listDriveFolderItems(ctx, accessToken, provider, current, job.CursorJSON)
	if err != nil {
		return err
	}

	listIndex := int(jsonNumber(job.CursorJSON["listIndex"]))
	for i := listIndex; i < len(folderItems) && batch < driveImportBatchSize(); i++ {
		item := folderItems[i]
		if alreadyImported(store, item.ID) {
			continue
		}
		relPath := path.Join(current.Path, sanitizeDrivePath(item.Name))
		targetPath := path.Join(root, relPath)
		if item.IsFolder {
			if err := d.nc.CreateFolder(ctx, ncUserID, targetPath); err != nil {
				if markErr := store.MarkFailed(ctx, item.ID, err.Error(), relPath); markErr != nil {
					return markErr
				}
				incJobStat(job.StatsJSON, "failed")
				batch++
				continue
			}
			if err := store.MarkPath(ctx, item.ID, relPath); err != nil {
				return err
			}
			queue = enqueueDriveFolder(queue, driveFolderRef{ID: item.ID, Path: relPath})
		} else {
			if item.Export {
				content, contentType, fileName, err := d.downloadGoogleExport(ctx, accessToken, item)
				if err != nil {
					skipped++
					if err := store.MarkSkipped(ctx, item.ID, "export: "+err.Error(), relPath); err != nil {
						return err
					}
					batch++
					continue
				}
				targetPath = path.Join(path.Dir(targetPath), fileName)
				relPath = path.Join(path.Dir(relPath), fileName)
				if err := d.nc.Upload(ctx, ncUserID, targetPath, content, contentType); err != nil {
					if markErr := store.MarkFailed(ctx, item.ID, err.Error(), relPath); markErr != nil {
						return markErr
					}
					incJobStat(job.StatsJSON, "failed")
					batch++
					continue
				}
				exported++
				if pdfMime, pdfExt, ok := googleSlidesPDFExport(item.MimeType); ok {
					pdfItem := item
					pdfItem.ExportMime = pdfMime
					pdfItem.ExportExt = pdfExt
					if pdfContent, pdfType, pdfName, err := d.downloadGoogleExport(ctx, accessToken, pdfItem); err == nil {
						pdfRel := path.Join(path.Dir(relPath), pdfName)
						pdfTarget := path.Join(root, pdfRel)
						if err := d.nc.Upload(ctx, ncUserID, pdfTarget, pdfContent, pdfType); err == nil {
							if err := store.MarkPath(ctx, item.ID+"_pdf", pdfRel); err != nil {
								return err
							}
						}
					}
				}
			} else {
				if item.Size > maxDriveFileBytes {
					skipped++
					reason := fmt.Sprintf("file exceeds %d byte limit", maxDriveFileBytes)
					if err := store.MarkSkipped(ctx, item.ID, reason, relPath); err != nil {
						return err
					}
					batch++
					continue
				}
				content, contentType, err := d.downloadDriveFile(ctx, accessToken, item)
				if err != nil {
					if markErr := store.MarkFailed(ctx, item.ID, err.Error(), relPath); markErr != nil {
						return markErr
					}
					incJobStat(job.StatsJSON, "failed")
					batch++
					continue
				}
				if err := d.nc.Upload(ctx, ncUserID, targetPath, content, contentType); err != nil {
					if markErr := store.MarkFailed(ctx, item.ID, err.Error(), relPath); markErr != nil {
						return markErr
					}
					incJobStat(job.StatsJSON, "failed")
					batch++
					continue
				}
			}
		}
		if err := store.MarkImported(ctx, item.ID); err != nil {
			return err
		}
		if !item.IsFolder {
			if err := store.MarkPath(ctx, item.ID, relPath); err != nil {
				return err
			}
		}
		imported++
		batch++
	}

	for _, sub := range subfolders {
		relPath := path.Join(current.Path, sanitizeDrivePath(sub.Name))
		queue = enqueueDriveFolder(queue, driveFolderRef{ID: sub.ID, Path: relPath})
	}
	writeDriveFolderQueue(job.CursorJSON, queue)

	job.StatsJSON["imported"] = imported
	job.StatsJSON["skipped"] = skipped
	job.StatsJSON["exported"] = exported

	if listIndex+batch < len(folderItems) {
		job.CursorJSON["listIndex"] = float64(listIndex + batch)
		return update("pending", job.CursorJSON, job.StatsJSON, "")
	}
	delete(job.CursorJSON, "listIndex")

	if nextCursor != "" {
		if provider == "google" {
			job.CursorJSON["pageToken"] = nextCursor
		} else {
			job.CursorJSON["nextLink"] = nextCursor
		}
		return update("pending", job.CursorJSON, job.StatsJSON, "")
	}
	delete(job.CursorJSON, "pageToken")
	delete(job.CursorJSON, "nextLink")

	job.CursorJSON["folderIndex"] = float64(folderIndex + 1)
	delete(job.CursorJSON, "listIndex")
	return update("pending", job.CursorJSON, job.StatsJSON, "")
}

type driveItem struct {
	ID         string
	Name       string
	ParentID   string
	IsFolder   bool
	Size       int64
	MimeType   string
	Download   string
	Export     bool
	ExportMime string
	ExportExt  string
}

type driveSubfolder struct {
	ID   string
	Name string
}

func (d *DriveImporter) listDriveFolderItems(ctx context.Context, accessToken, provider string, folder driveFolderRef, cursor map[string]any) ([]driveItem, string, []driveSubfolder, error) {
	switch provider {
	case "google":
		pageToken, _ := cursor["pageToken"].(string)
		q := url.QueryEscape("'" + folder.ID + "' in parents and trashed=false")
		listURL := "https://www.googleapis.com/drive/v3/files?pageSize=100&fields=nextPageToken,files(id,name,mimeType,size)&q=" + q
		if pageToken != "" {
			listURL += "&pageToken=" + url.QueryEscape(pageToken)
		}
		body, err := apiGet(ctx, d.client, listURL, accessToken)
		if err != nil {
			return nil, "", nil, err
		}
		var parsed struct {
			Files         []struct {
				ID       string `json:"id"`
				Name     string `json:"name"`
				MimeType string `json:"mimeType"`
				Size     string `json:"size"`
			} `json:"files"`
			NextPageToken string `json:"nextPageToken"`
		}
		if err := json.Unmarshal(body, &parsed); err != nil {
			return nil, "", nil, err
		}
		out := make([]driveItem, 0, len(parsed.Files))
		for _, f := range parsed.Files {
			size := int64(0)
			if f.Size != "" {
				fmt.Sscan(f.Size, &size)
			}
			item := driveItem{
				ID:       f.ID,
				Name:     f.Name,
				IsFolder: f.MimeType == "application/vnd.google-apps.folder",
				Size:     size,
				MimeType: f.MimeType,
			}
			if item.IsFolder {
				out = append(out, item)
				continue
			}
			if exportMime, ext, ok := googleWorkspaceExport(f.MimeType); ok {
				item.Export = true
				item.ExportMime = exportMime
				item.ExportExt = ext
				item.Name = driveExportFileName(f.Name, ext)
			} else {
				item.Download = "https://www.googleapis.com/drive/v3/files/" + url.PathEscape(f.ID) + "?alt=media"
			}
			out = append(out, item)
		}
		return out, parsed.NextPageToken, nil, nil
	default:
		nextLink, _ := cursor["nextLink"].(string)
		var listURL string
		if folder.ID == "root" {
			listURL = graphMicrosoftURL(d.userUPN, "/drive/root/children?$top=100&$select=id,name,folder,file,size")
		} else {
			listURL = graphMicrosoftURL(d.userUPN, "/drive/items/"+url.PathEscape(folder.ID)+"/children?$top=100&$select=id,name,folder,file,size")
		}
		if nextLink != "" {
			listURL = nextLink
		}
		body, err := apiGet(ctx, d.client, listURL, accessToken)
		if err != nil {
			return nil, "", nil, err
		}
		var parsed struct {
			Value []struct {
				ID     string `json:"id"`
				Name   string `json:"name"`
				Folder *struct {
					ChildCount int `json:"childCount"`
				} `json:"folder"`
				File *struct {
					MimeType string `json:"mimeType"`
				} `json:"file"`
				Size int64 `json:"size"`
			} `json:"value"`
			NextLink string `json:"@odata.nextLink"`
		}
		if err := json.Unmarshal(body, &parsed); err != nil {
			return nil, "", nil, err
		}
		out := make([]driveItem, 0, len(parsed.Value))
		var subs []driveSubfolder
		for _, f := range parsed.Value {
			if f.Folder != nil {
				out = append(out, driveItem{ID: f.ID, Name: f.Name, IsFolder: true})
				if f.Folder.ChildCount > 0 {
					subs = append(subs, driveSubfolder{ID: f.ID, Name: f.Name})
				}
				continue
			}
			mime := ""
			if f.File != nil {
				mime = f.File.MimeType
			}
			out = append(out, driveItem{
				ID:       f.ID,
				Name:     f.Name,
				Size:     f.Size,
				MimeType: mime,
				Download: graphMicrosoftURL(d.userUPN, "/drive/items/"+url.PathEscape(f.ID)+"/content"),
			})
		}
		return out, parsed.NextLink, subs, nil
	}
}

func (d *DriveImporter) downloadDriveFile(ctx context.Context, accessToken string, item driveItem) (io.ReadCloser, string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, item.Download, nil)
	if err != nil {
		return nil, "", err
	}
	req.Header.Set("Authorization", "Bearer "+accessToken)
	resp, err := migrationDo(ctx, d.client, req)
	if err != nil {
		return nil, "", fmt.Errorf("download %s: %w", item.Name, err)
	}
	contentType := resp.Header.Get("Content-Type")
	if contentType == "" {
		contentType = item.MimeType
	}
	if contentType == "" {
		contentType = "application/octet-stream"
	}
	return resp.Body, contentType, nil
}

func (d *DriveImporter) downloadGoogleExport(ctx context.Context, accessToken string, item driveItem) (io.ReadCloser, string, string, error) {
	exportURL := fmt.Sprintf(
		"https://www.googleapis.com/drive/v3/files/%s/export?mimeType=%s",
		url.PathEscape(item.ID),
		url.QueryEscape(item.ExportMime),
	)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, exportURL, nil)
	if err != nil {
		return nil, "", "", err
	}
	req.Header.Set("Authorization", "Bearer "+accessToken)
	resp, err := migrationDo(ctx, d.client, req)
	if err != nil {
		return nil, "", "", fmt.Errorf("export %s: %w", item.Name, err)
	}
	contentType := resp.Header.Get("Content-Type")
	if contentType == "" {
		contentType = item.ExportMime
	}
	return resp.Body, contentType, driveExportFileName(item.Name, item.ExportExt), nil
}

func sanitizeDrivePath(name string) string {
	name = strings.TrimSpace(name)
	name = strings.ReplaceAll(name, "/", "-")
	name = strings.ReplaceAll(name, "\\", "-")
	if name == "" {
		return "untitled"
	}
	return name
}