// usage-report queries a hold service and generates a storage usage report
// grouped by user, with unique layers and totals.
//
// Usage:
//
//	go run ./cmd/usage-report --hold https://hold01.atcr.io
//	go run ./cmd/usage-report --hold https://hold01.atcr.io --from-manifests
//	go run ./cmd/usage-report --hold https://hold01.atcr.io --list-blobs
package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"slices"
	"sort"
	"strings"
	"time"
)

// LayerRecord matches the io.atcr.hold.layer record structure
type LayerRecord struct {
	Type      string `json:"$type"`
	Digest    string `json:"digest"`
	Size      int64  `json:"size"`
	MediaType string `json:"mediaType"`
	Manifest  string `json:"manifest"`
	UserDID   string `json:"userDid"`
	CreatedAt string `json:"createdAt"`
}

// ManifestRecord matches the io.atcr.manifest record structure
type ManifestRecord struct {
	Type       string `json:"$type"`
	Repository string `json:"repository"`
	Digest     string `json:"digest"`
	HoldDID    string `json:"holdDid"`
	Config     *struct {
		Digest string `json:"digest"`
		Size   int64  `json:"size"`
	} `json:"config"`
	Layers []struct {
		Digest    string `json:"digest"`
		Size      int64  `json:"size"`
		MediaType string `json:"mediaType"`
	} `json:"layers"`
	Manifests []struct {
		Digest string `json:"digest"`
		Size   int64  `json:"size"`
	} `json:"manifests"`
	CreatedAt string `json:"createdAt"`
}

// CrewRecord matches the io.atcr.hold.crew record structure
type CrewRecord struct {
	Member      string   `json:"member"`
	Role        string   `json:"role"`
	Permissions []string `json:"permissions"`
	AddedAt     string   `json:"addedAt"`
}

// ListRecordsResponse is the response from com.atproto.repo.listRecords
type ListRecordsResponse struct {
	Records []struct {
		URI   string          `json:"uri"`
		CID   string          `json:"cid"`
		Value json.RawMessage `json:"value"`
	} `json:"records"`
	Cursor string `json:"cursor,omitempty"`
}

// UserUsage tracks storage for a single user
type UserUsage struct {
	DID          string
	Handle       string
	UniqueLayers map[string]int64 // digest -> size
	TotalSize    int64
	LayerCount   int
	Repositories map[string]bool // unique repos
}

var client = &http.Client{Timeout: 30 * time.Second}

// BlobInfo represents a single blob with its metadata
type BlobInfo struct {
	Digest    string
	Size      int64
	MediaType string
	UserDID   string
	Handle    string
}

func main() {
	holdURL := flag.String("hold", "https://hold01.atcr.io", "Hold service URL")
	fromManifests := flag.Bool("from-manifests", false, "Calculate usage from user manifests instead of hold layer records (more accurate but slower)")
	listBlobs := flag.Bool("list-blobs", false, "List all individual blobs sorted by size (largest first)")
	flag.Parse()

	// Normalize URL
	baseURL := strings.TrimSuffix(*holdURL, "/")

	fmt.Printf("Querying %s...\n\n", baseURL)

	// First, get the hold's DID
	holdDID, err := getHoldDID(baseURL)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to get hold DID: %v\n", err)
		os.Exit(1)
	}
	fmt.Printf("Hold DID: %s\n\n", holdDID)

	// If --list-blobs flag is set, run blob listing mode
	if *listBlobs {
		listAllBlobs(baseURL, holdDID)
		return
	}

	var userUsage map[string]*UserUsage

	if *fromManifests {
		fmt.Println("=== Calculating from user manifests (bypasses layer record bug) ===")
		userUsage, err = calculateFromManifests(baseURL, holdDID)
	} else {
		fmt.Println("=== Calculating from hold layer records ===")
		fmt.Println("NOTE: May undercount app-password users due to layer record bug")
		fmt.Println("      Use --from-manifests for more accurate results")

		userUsage, err = calculateFromLayerRecords(baseURL, holdDID)
	}

	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to calculate usage: %v\n", err)
		os.Exit(1)
	}

	// Resolve DIDs to handles
	fmt.Println("\n\nResolving DIDs to handles...")
	for _, usage := range userUsage {
		handle, err := resolveDIDToHandle(usage.DID)
		if err != nil {
			usage.Handle = usage.DID
		} else {
			usage.Handle = handle
		}
	}

	// Convert to slice and sort by total size (descending)
	var sorted []*UserUsage
	for _, u := range userUsage {
		sorted = append(sorted, u)
	}
	sort.Slice(sorted, func(i, j int) bool {
		return sorted[i].TotalSize > sorted[j].TotalSize
	})

	// Print report
	fmt.Println("\n========================================")
	fmt.Println("STORAGE USAGE REPORT")
	fmt.Println("========================================")

	var grandTotal int64
	var grandLayers int
	for _, u := range sorted {
		grandTotal += u.TotalSize
		grandLayers += u.LayerCount
	}

	fmt.Printf("\nTotal Users: %d\n", len(sorted))
	fmt.Printf("Total Unique Layers: %d\n", grandLayers)
	fmt.Printf("Total Storage: %s\n\n", humanSize(grandTotal))

	fmt.Println("BY USER (sorted by storage):")
	fmt.Println("----------------------------------------")
	for i, u := range sorted {
		fmt.Printf("%3d. %s\n", i+1, u.Handle)
		fmt.Printf("     DID: %s\n", u.DID)
		fmt.Printf("     Unique Layers: %d\n", u.LayerCount)
		fmt.Printf("     Total Size: %s\n", humanSize(u.TotalSize))
		if len(u.Repositories) > 0 {
			var repos []string
			for r := range u.Repositories {
				repos = append(repos, r)
			}
			sort.Strings(repos)
			fmt.Printf("     Repositories: %s\n", strings.Join(repos, ", "))
		}
		pct := float64(0)
		if grandTotal > 0 {
			pct = float64(u.TotalSize) / float64(grandTotal) * 100
		}
		fmt.Printf("     Share: %.1f%%\n\n", pct)
	}

	// Output CSV format for easy analysis
	fmt.Println("\n========================================")
	fmt.Println("CSV FORMAT")
	fmt.Println("========================================")
	fmt.Println("handle,did,unique_layers,total_bytes,total_human,repositories")
	for _, u := range sorted {
		var repos []string
		for r := range u.Repositories {
			repos = append(repos, r)
		}
		sort.Strings(repos)
		fmt.Printf("%s,%s,%d,%d,%s,\"%s\"\n", u.Handle, u.DID, u.LayerCount, u.TotalSize, humanSize(u.TotalSize), strings.Join(repos, ";"))
	}
}

// listAllBlobs fetches all blobs and lists them sorted by size (largest first)
func listAllBlobs(baseURL, holdDID string) {
	fmt.Println("=== Fetching all blob records ===")

	layers, err := fetchAllLayerRecords(baseURL, holdDID)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to fetch layer records: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Fetched %d layer records\n", len(layers))

	// Deduplicate by digest, keeping track of first seen user
	blobMap := make(map[string]*BlobInfo)
	for _, layer := range layers {
		if existing, exists := blobMap[layer.Digest]; exists {
			// If we have a record with a user DID and existing doesn't, prefer this one
			if existing.UserDID == "" && layer.UserDID != "" {
				existing.UserDID = layer.UserDID
			}
			continue
		}
		blobMap[layer.Digest] = &BlobInfo{
			Digest:    layer.Digest,
			Size:      layer.Size,
			MediaType: layer.MediaType,
			UserDID:   layer.UserDID,
		}
	}

	// Convert to slice
	var blobs []*BlobInfo
	for _, b := range blobMap {
		blobs = append(blobs, b)
	}

	// Sort by size (largest first)
	sort.Slice(blobs, func(i, j int) bool {
		return blobs[i].Size > blobs[j].Size
	})

	fmt.Printf("Found %d unique blobs\n\n", len(blobs))

	// Resolve DIDs to handles (batch for efficiency)
	fmt.Println("Resolving DIDs to handles...")
	didToHandle := make(map[string]string)
	for _, b := range blobs {
		if b.UserDID == "" {
			continue
		}
		if _, exists := didToHandle[b.UserDID]; !exists {
			handle, err := resolveDIDToHandle(b.UserDID)
			if err != nil {
				didToHandle[b.UserDID] = b.UserDID
			} else {
				didToHandle[b.UserDID] = handle
			}
		}
		b.Handle = didToHandle[b.UserDID]
	}

	// Calculate total
	var totalSize int64
	for _, b := range blobs {
		totalSize += b.Size
	}

	// Print report
	fmt.Println("\n========================================")
	fmt.Println("BLOB SIZE REPORT (sorted largest to smallest)")
	fmt.Println("========================================")
	fmt.Printf("\nTotal Unique Blobs: %d\n", len(blobs))
	fmt.Printf("Total Storage: %s\n\n", humanSize(totalSize))

	fmt.Println("BLOBS:")
	fmt.Println("----------------------------------------")
	for i, b := range blobs {
		pct := float64(0)
		if totalSize > 0 {
			pct = float64(b.Size) / float64(totalSize) * 100
		}
		owner := b.Handle
		if owner == "" {
			owner = "(unknown)"
		}
		fmt.Printf("%4d. %s\n", i+1, humanSize(b.Size))
		fmt.Printf("      Digest: %s\n", b.Digest)
		fmt.Printf("      Owner: %s\n", owner)
		if b.MediaType != "" {
			fmt.Printf("      Type: %s\n", b.MediaType)
		}
		fmt.Printf("      Share: %.2f%%\n\n", pct)
	}

	// Output CSV format
	fmt.Println("\n========================================")
	fmt.Println("CSV FORMAT")
	fmt.Println("========================================")
	fmt.Println("rank,size_bytes,size_human,digest,owner,media_type,share_pct")
	for i, b := range blobs {
		pct := float64(0)
		if totalSize > 0 {
			pct = float64(b.Size) / float64(totalSize) * 100
		}
		owner := b.Handle
		if owner == "" {
			owner = ""
		}
		fmt.Printf("%d,%d,%s,%s,%s,%s,%.2f\n", i+1, b.Size, humanSize(b.Size), b.Digest, owner, b.MediaType, pct)
	}
}

// calculateFromLayerRecords uses the hold's layer records (original method)
func calculateFromLayerRecords(baseURL, holdDID string) (map[string]*UserUsage, error) {
	layers, err := fetchAllLayerRecords(baseURL, holdDID)
	if err != nil {
		return nil, err
	}

	fmt.Printf("Fetched %d layer records\n", len(layers))

	userUsage := make(map[string]*UserUsage)
	for _, layer := range layers {
		if layer.UserDID == "" {
			continue
		}

		usage, exists := userUsage[layer.UserDID]
		if !exists {
			usage = &UserUsage{
				DID:          layer.UserDID,
				UniqueLayers: make(map[string]int64),
				Repositories: make(map[string]bool),
			}
			userUsage[layer.UserDID] = usage
		}

		if _, seen := usage.UniqueLayers[layer.Digest]; !seen {
			usage.UniqueLayers[layer.Digest] = layer.Size
			usage.TotalSize += layer.Size
			usage.LayerCount++
		}
	}

	return userUsage, nil
}

// calculateFromManifests queries crew members and fetches their manifests from their PDSes
func calculateFromManifests(baseURL, holdDID string) (map[string]*UserUsage, error) {
	// Get all crew members
	crewDIDs, err := fetchCrewMembers(baseURL, holdDID)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch crew: %w", err)
	}

	// Also get captain
	captainDID, err := fetchCaptain(baseURL, holdDID)
	if err == nil && captainDID != "" {
		// Add captain to list if not already there
		found := slices.Contains(crewDIDs, captainDID)
		if !found {
			crewDIDs = append(crewDIDs, captainDID)
		}
	}

	fmt.Printf("Found %d users (crew + captain)\n", len(crewDIDs))

	userUsage := make(map[string]*UserUsage)

	for _, did := range crewDIDs {
		fmt.Printf("  Checking manifests for %s...", did)

		// Resolve DID to PDS
		pdsEndpoint, err := resolveDIDToPDS(did)
		if err != nil {
			fmt.Printf(" (failed to resolve PDS: %v)\n", err)
			continue
		}

		// Fetch manifests that use this hold
		manifests, err := fetchUserManifestsForHold(pdsEndpoint, did, holdDID)
		if err != nil {
			fmt.Printf(" (failed to fetch manifests: %v)\n", err)
			continue
		}

		if len(manifests) == 0 {
			fmt.Printf(" 0 manifests\n")
			continue
		}

		// Calculate unique layers across all manifests
		usage := &UserUsage{
			DID:          did,
			UniqueLayers: make(map[string]int64),
			Repositories: make(map[string]bool),
		}

		for _, m := range manifests {
			usage.Repositories[m.Repository] = true

			// Add config blob
			if m.Config != nil {
				if _, seen := usage.UniqueLayers[m.Config.Digest]; !seen {
					usage.UniqueLayers[m.Config.Digest] = m.Config.Size
					usage.TotalSize += m.Config.Size
					usage.LayerCount++
				}
			}

			// Add layers
			for _, layer := range m.Layers {
				if _, seen := usage.UniqueLayers[layer.Digest]; !seen {
					usage.UniqueLayers[layer.Digest] = layer.Size
					usage.TotalSize += layer.Size
					usage.LayerCount++
				}
			}
		}

		fmt.Printf(" %d manifests, %d unique layers, %s\n", len(manifests), usage.LayerCount, humanSize(usage.TotalSize))

		if usage.LayerCount > 0 {
			userUsage[did] = usage
		}
	}

	return userUsage, nil
}

// fetchCrewMembers gets all crew member DIDs from the hold
func fetchCrewMembers(baseURL, holdDID string) ([]string, error) {
	var dids []string
	seen := make(map[string]bool)

	cursor := ""
	for {
		u := fmt.Sprintf("%s/xrpc/com.atproto.repo.listRecords", baseURL)
		params := url.Values{}
		params.Set("repo", holdDID)
		params.Set("collection", "io.atcr.hold.crew")
		params.Set("limit", "100")
		if cursor != "" {
			params.Set("cursor", cursor)
		}

		resp, err := client.Get(u + "?" + params.Encode())
		if err != nil {
			return nil, err
		}

		var listResp ListRecordsResponse
		if err := json.NewDecoder(resp.Body).Decode(&listResp); err != nil {
			resp.Body.Close()
			return nil, err
		}
		resp.Body.Close()

		for _, rec := range listResp.Records {
			var crew CrewRecord
			if err := json.Unmarshal(rec.Value, &crew); err != nil {
				continue
			}
			if crew.Member != "" && !seen[crew.Member] {
				seen[crew.Member] = true
				dids = append(dids, crew.Member)
			}
		}

		if listResp.Cursor == "" || len(listResp.Records) < 100 {
			break
		}
		cursor = listResp.Cursor
	}

	return dids, nil
}

// fetchCaptain gets the captain DID from the hold
func fetchCaptain(baseURL, holdDID string) (string, error) {
	u := fmt.Sprintf("%s/xrpc/com.atproto.repo.getRecord?repo=%s&collection=io.atcr.hold.captain&rkey=self",
		baseURL, url.QueryEscape(holdDID))

	resp, err := client.Get(u)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("status %d", resp.StatusCode)
	}

	var result struct {
		Value struct {
			Owner string `json:"owner"`
		} `json:"value"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return "", err
	}

	return result.Value.Owner, nil
}

// fetchUserManifestsForHold fetches all manifests from a user's PDS that use the specified hold
func fetchUserManifestsForHold(pdsEndpoint, userDID, holdDID string) ([]ManifestRecord, error) {
	var manifests []ManifestRecord
	cursor := ""

	for {
		u := fmt.Sprintf("%s/xrpc/com.atproto.repo.listRecords", pdsEndpoint)
		params := url.Values{}
		params.Set("repo", userDID)
		params.Set("collection", "io.atcr.manifest")
		params.Set("limit", "100")
		if cursor != "" {
			params.Set("cursor", cursor)
		}

		resp, err := client.Get(u + "?" + params.Encode())
		if err != nil {
			return nil, err
		}

		if resp.StatusCode != http.StatusOK {
			resp.Body.Close()
			return nil, fmt.Errorf("status %d", resp.StatusCode)
		}

		var listResp ListRecordsResponse
		if err := json.NewDecoder(resp.Body).Decode(&listResp); err != nil {
			resp.Body.Close()
			return nil, err
		}
		resp.Body.Close()

		for _, rec := range listResp.Records {
			var m ManifestRecord
			if err := json.Unmarshal(rec.Value, &m); err != nil {
				continue
			}
			// Only include manifests for this hold
			if m.HoldDID == holdDID {
				manifests = append(manifests, m)
			}
		}

		if listResp.Cursor == "" || len(listResp.Records) < 100 {
			break
		}
		cursor = listResp.Cursor
	}

	return manifests, nil
}

// getHoldDID fetches the hold's DID from /.well-known/atproto-did
func getHoldDID(baseURL string) (string, error) {
	resp, err := http.Get(baseURL + "/.well-known/atproto-did")
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("unexpected status: %d", resp.StatusCode)
	}

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", err
	}

	return strings.TrimSpace(string(body)), nil
}

// fetchAllLayerRecords fetches all layer records with pagination
func fetchAllLayerRecords(baseURL, holdDID string) ([]LayerRecord, error) {
	var allLayers []LayerRecord
	cursor := ""
	limit := 100

	for {
		u := fmt.Sprintf("%s/xrpc/com.atproto.repo.listRecords", baseURL)
		params := url.Values{}
		params.Set("repo", holdDID)
		params.Set("collection", "io.atcr.hold.layer")
		params.Set("limit", fmt.Sprintf("%d", limit))
		if cursor != "" {
			params.Set("cursor", cursor)
		}

		fullURL := u + "?" + params.Encode()
		fmt.Printf("  Fetching: %s\n", fullURL)

		resp, err := client.Get(fullURL)
		if err != nil {
			return nil, fmt.Errorf("request failed: %w", err)
		}

		if resp.StatusCode != http.StatusOK {
			body, _ := io.ReadAll(resp.Body)
			resp.Body.Close()
			return nil, fmt.Errorf("unexpected status %d: %s", resp.StatusCode, string(body))
		}

		var listResp ListRecordsResponse
		if err := json.NewDecoder(resp.Body).Decode(&listResp); err != nil {
			resp.Body.Close()
			return nil, fmt.Errorf("decode failed: %w", err)
		}
		resp.Body.Close()

		for _, rec := range listResp.Records {
			var layer LayerRecord
			if err := json.Unmarshal(rec.Value, &layer); err != nil {
				fmt.Fprintf(os.Stderr, "Warning: failed to parse layer record: %v\n", err)
				continue
			}
			allLayers = append(allLayers, layer)
		}

		fmt.Printf("  Got %d records (total: %d)\n", len(listResp.Records), len(allLayers))

		if listResp.Cursor == "" || len(listResp.Records) < limit {
			break
		}
		cursor = listResp.Cursor
	}

	return allLayers, nil
}

// resolveDIDToHandle resolves a DID to a handle using the PLC directory or did:web
func resolveDIDToHandle(did string) (string, error) {
	if after, ok := strings.CutPrefix(did, "did:web:"); ok {
		return after, nil
	}

	if strings.HasPrefix(did, "did:plc:") {
		plcURL := "https://plc.directory/" + did
		resp, err := client.Get(plcURL)
		if err != nil {
			return "", fmt.Errorf("PLC query failed: %w", err)
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			return "", fmt.Errorf("PLC returned status %d", resp.StatusCode)
		}

		var plcDoc struct {
			AlsoKnownAs []string `json:"alsoKnownAs"`
		}
		if err := json.NewDecoder(resp.Body).Decode(&plcDoc); err != nil {
			return "", fmt.Errorf("failed to parse PLC response: %w", err)
		}

		for _, aka := range plcDoc.AlsoKnownAs {
			if after, ok := strings.CutPrefix(aka, "at://"); ok {
				return after, nil
			}
		}

		return did, nil
	}

	return did, nil
}

// resolveDIDToPDS resolves a DID to its PDS endpoint
func resolveDIDToPDS(did string) (string, error) {
	if after, ok := strings.CutPrefix(did, "did:web:"); ok {
		// did:web:example.com -> https://example.com
		// did:web:host%3A8080 -> http://host:8080
		domain := after
		domain = strings.ReplaceAll(domain, "%3A", ":")
		scheme := "https"
		if strings.Contains(domain, ":") {
			scheme = "http"
		}
		return scheme + "://" + domain, nil
	}

	if strings.HasPrefix(did, "did:plc:") {
		plcURL := "https://plc.directory/" + did
		resp, err := client.Get(plcURL)
		if err != nil {
			return "", fmt.Errorf("PLC query failed: %w", err)
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			return "", fmt.Errorf("PLC returned status %d", resp.StatusCode)
		}

		var plcDoc struct {
			Service []struct {
				ID              string `json:"id"`
				Type            string `json:"type"`
				ServiceEndpoint string `json:"serviceEndpoint"`
			} `json:"service"`
		}
		if err := json.NewDecoder(resp.Body).Decode(&plcDoc); err != nil {
			return "", fmt.Errorf("failed to parse PLC response: %w", err)
		}

		for _, svc := range plcDoc.Service {
			if svc.Type == "AtprotoPersonalDataServer" {
				return svc.ServiceEndpoint, nil
			}
		}

		return "", fmt.Errorf("no PDS found in DID document")
	}

	return "", fmt.Errorf("unsupported DID method")
}

// humanSize converts bytes to human-readable format
func humanSize(bytes int64) string {
	const (
		KB = 1024
		MB = 1024 * KB
		GB = 1024 * MB
		TB = 1024 * GB
	)

	switch {
	case bytes >= TB:
		return fmt.Sprintf("%.2f TB", float64(bytes)/TB)
	case bytes >= GB:
		return fmt.Sprintf("%.2f GB", float64(bytes)/GB)
	case bytes >= MB:
		return fmt.Sprintf("%.2f MB", float64(bytes)/MB)
	case bytes >= KB:
		return fmt.Sprintf("%.2f KB", float64(bytes)/KB)
	default:
		return fmt.Sprintf("%d B", bytes)
	}
}