package main

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"runtime"
	"strings"
	"time"

	"github.com/bluesky-social/indigo/atproto/atclient"
	"github.com/bluesky-social/indigo/atproto/auth/oauth"
	"github.com/bluesky-social/indigo/atproto/syntax"
	"github.com/spf13/cobra"
)

func main() {
	rootCmd := &cobra.Command{
		Use:   "atvouch",
		Short: "AT Protocol vouching tool",
	}

	loginCmd := &cobra.Command{
		Use:   "login <handle>",
		Short: "Authenticate with your PDS via OAuth",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			return login(cmd.Context(), args[0])
		},
	}

	meCmd := &cobra.Command{
		Use:   "me",
		Short: "Show current authenticated session info",
		Args:  cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			return me(cmd.Context())
		},
	}

	createCmd := &cobra.Command{
		Use:   "create <handle>",
		Short: "Vouch for a user by their handle",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			return create(cmd.Context(), args[0])
		},
	}

	checkCmd := &cobra.Command{
		Use:   "check <handle>",
		Short: "Check vouch paths to a user",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			return check(cmd.Context(), args[0])
		},
	}

	rootCmd.AddCommand(loginCmd, meCmd, createCmd, checkCmd)

	if err := rootCmd.ExecuteContext(context.Background()); err != nil {
		os.Exit(1)
	}
}

func newStore() (*Store, error) {
	return NewStore()
}

func newOAuthClient(store *Store, callbackURL string) *oauth.ClientApp {
	config := oauth.NewLocalhostConfig(callbackURL, []string{
		"atproto",
		"repo:dev.atvouch.graph.vouch",
	})
	return oauth.NewClientApp(&config, store)
}

func login(ctx context.Context, handle string) error {
	store, err := newStore()
	if err != nil {
		return err
	}

	// Start the callback server on a random available port
	callbackCh := make(chan url.Values, 1)
	port, server, err := listenForCallback(ctx, callbackCh)
	if err != nil {
		return err
	}
	defer server.Close()

	callbackURL := fmt.Sprintf("http://127.0.0.1:%d/callback", port)
	oauthClient := newOAuthClient(store, callbackURL)

	// Start the OAuth flow
	fmt.Printf("Logging in as %s...\n", handle)
	authURL, err := oauthClient.StartAuthFlow(ctx, handle)
	if err != nil {
		return fmt.Errorf("starting auth flow: %w", err)
	}

	// Open the browser to the authorization URL
	fmt.Printf("Opening browser...\n")
	if !strings.HasPrefix(authURL, "https://") {
		return fmt.Errorf("unexpected non-https auth URL")
	}
	if err := openBrowser(authURL); err != nil {
		fmt.Printf("Could not open browser automatically.\nPlease visit: %s\n", authURL)
	}

	// Wait for the OAuth callback
	fmt.Println("Waiting for authorization...")
	params := <-callbackCh

	// Exchange the authorization code for a session
	sessData, err := oauthClient.ProcessCallback(ctx, params)
	if err != nil {
		return fmt.Errorf("processing callback: %w", err)
	}

	// Mark this as the active session
	if err := store.SetActive(sessData.AccountDID, sessData.SessionID); err != nil {
		return fmt.Errorf("saving active session: %w", err)
	}

	fmt.Printf("Logged in as %s (%s)\n", handle, sessData.AccountDID)
	return nil
}

func resumeSession(ctx context.Context) (*oauth.ClientSession, error) {
	store, err := newStore()
	if err != nil {
		return nil, err
	}

	active, err := store.GetActive()
	if err != nil {
		return nil, err
	}

	// We need a callback URL to construct the client config, but we won't
	// actually start any auth flow here. Use a dummy port.
	callbackURL := "http://127.0.0.1:0/callback"
	oauthClient := newOAuthClient(store, callbackURL)

	session, err := oauthClient.ResumeSession(ctx, active.DID, active.SessionID)
	if err != nil {
		return nil, fmt.Errorf("resuming session: %w", err)
	}

	return session, nil
}

func me(ctx context.Context) error {
	session, err := resumeSession(ctx)
	if err != nil {
		return err
	}

	client := session.APIClient()
	var resp json.RawMessage
	if err := client.Get(ctx, "com.atproto.server.getSession", nil, &resp); err != nil {
		return fmt.Errorf("fetching session: %w", err)
	}

	// Pretty-print the response
	var pretty bytes.Buffer
	json.Indent(&pretty, resp, "", "  ")
	fmt.Println(pretty.String())

	return nil
}

func create(ctx context.Context, handle string) error {
	session, err := resumeSession(ctx)
	if err != nil {
		return err
	}

	client := session.APIClient()

	// Resolve handle to DID
	var resolveResp struct {
		DID string `json:"did"`
	}
	if err := client.Get(ctx, "com.atproto.identity.resolveHandle", map[string]any{
		"handle": handle,
	}, &resolveResp); err != nil {
		return fmt.Errorf("resolving handle %q: %w", handle, err)
	}

	subjectDID, err := syntax.ParseDID(resolveResp.DID)
	if err != nil {
		return fmt.Errorf("invalid DID from resolution: %w", err)
	}

	// Check if a vouch already exists for this subject
	var existingRecord struct {
		URI   string `json:"uri"`
		Value any    `json:"value"`
	}
	err = client.Get(ctx, "com.atproto.repo.getRecord", map[string]any{
		"repo":       session.Data.AccountDID,
		"collection": "dev.atvouch.graph.vouch",
		"rkey":       subjectDID.String(),
	}, &existingRecord)
	if err == nil {
		fmt.Printf("You have already vouched for %s (%s)\n", handle, subjectDID)
		fmt.Printf("Record: %s\n", existingRecord.URI)
		return nil
	}

	// Create the vouch record
	record := map[string]any{
		"$type":     "dev.atvouch.graph.vouch",
		"subject":   subjectDID.String(),
		"createdAt": time.Now().UTC().Format(time.RFC3339),
	}

	var createResp struct {
		URI string `json:"uri"`
		CID string `json:"cid"`
	}
	if err := client.Post(ctx, "com.atproto.repo.createRecord", map[string]any{
		"repo":       session.Data.AccountDID,
		"collection": "dev.atvouch.graph.vouch",
		"rkey":       subjectDID.String(),
		"record":     record,
	}, &createResp); err != nil {
		return fmt.Errorf("creating vouch record: %w", err)
	}

	fmt.Printf("Vouched for %s (%s)\n", handle, subjectDID)
	fmt.Printf("Record: %s\n", createResp.URI)

	return nil
}

// checkDeps holds injectable dependencies for the check logic.
type checkDeps struct {
	myDID              string
	resolveHandle      func(handle string) (string, error)
	resolveDidToHandle func(did string) (string, error)
	fetchVouchers      func(targetDID string) ([]string, error)
	listMyVouches      func() ([]string, error)
}

// checkResult holds the output of a check operation.
type checkResult struct {
	targetDID string
	paths     [][]string   // each path is a list of DIDs
	handleMap map[string]string // DID -> handle
}

func check(ctx context.Context, handle string) error {
	session, err := resumeSession(ctx)
	if err != nil {
		return err
	}

	client := session.APIClient()
	myDID := session.Data.AccountDID.String()

	deps := checkDeps{
		myDID:              myDID,
		resolveHandle:      slingshotResolveHandle,
		resolveDidToHandle: slingshotResolveDidToHandle,
		fetchVouchers:      fetchVouchersFromMicrocosm,
		listMyVouches: func() ([]string, error) {
			return listVouchSubjects(ctx, client, myDID)
		},
	}

	result, err := checkWithDeps(handle, deps)
	if err != nil {
		return err
	}

	fmt.Printf("Checking vouch paths to %s (%s)...\n", handle, result.targetDID)

	if result.paths == nil {
		fmt.Printf("\nyou -> %s\n", handle)
		return nil
	}

	if len(result.paths) == 0 {
		fmt.Println("no vouch routes found")
		return nil
	}

	fmt.Printf("\nFound %d vouch route(s):\n", len(result.paths))
	for _, path := range result.paths {
		parts := make([]string, len(path))
		for i, did := range path {
			parts[i] = result.handleMap[did]
		}
		fmt.Println(strings.Join(parts, " -> "))
	}

	return nil
}

// checkWithDeps contains the core check logic with injected dependencies.
// Returns a checkResult where paths == nil means direct vouch found,
// paths == empty means no routes, otherwise contains discovered paths.
func checkWithDeps(handle string, deps checkDeps) (*checkResult, error) {
	targetDID, err := deps.resolveHandle(handle)
	if err != nil {
		return nil, fmt.Errorf("resolving handle %q: %w", handle, err)
	}

	myVouches, err := deps.listMyVouches()
	if err != nil {
		return nil, fmt.Errorf("fetching your vouches: %w", err)
	}

	// Direct vouch check (depth 1)
	for _, did := range myVouches {
		if did == targetDID {
			return &checkResult{targetDID: targetDID, paths: nil}, nil
		}
	}

	// Build reverse graph from target using microcosm (up to 3 levels back)
	// reverseGraph[did] = set of DIDs that vouch for did
	reverseGraph := make(map[string]map[string]bool)

	// Level 1: who vouches for target
	level1, err := deps.fetchVouchers(targetDID)
	if err != nil {
		return nil, fmt.Errorf("querying microcosm: %w", err)
	}
	reverseGraph[targetDID] = toSet(level1)

	// Level 2: who vouches for each level-1 voucher
	level2DIDs := []string{}
	for _, did := range level1 {
		vouchers, err := deps.fetchVouchers(did)
		if err != nil {
			return nil, fmt.Errorf("querying microcosm: %w", err)
		}
		reverseGraph[did] = toSet(vouchers)
		level2DIDs = append(level2DIDs, vouchers...)
	}

	// Level 3: who vouches for each level-2 voucher
	for _, did := range level2DIDs {
		if _, exists := reverseGraph[did]; exists {
			continue // already fetched
		}
		vouchers, err := deps.fetchVouchers(did)
		if err != nil {
			return nil, fmt.Errorf("querying microcosm: %w", err)
		}
		reverseGraph[did] = toSet(vouchers)
	}

	// Find all paths: me -> (someone I vouch for) -> ... -> target
	myVouchSet := toSet(myVouches)
	var paths [][]string

	// Depth 2: me -> X -> target (X vouches for target, I vouch for X)
	for voucher := range reverseGraph[targetDID] {
		if myVouchSet[voucher] {
			paths = append(paths, []string{deps.myDID, voucher, targetDID})
		}
	}

	// Depth 3: me -> X -> Y -> target (Y vouches for target, X vouches for Y, I vouch for X)
	for yDID := range reverseGraph[targetDID] {
		for xDID := range reverseGraph[yDID] {
			if myVouchSet[xDID] {
				paths = append(paths, []string{deps.myDID, xDID, yDID, targetDID})
			}
		}
	}

	// Resolve all unique DIDs to handles for display
	handleMap := make(map[string]string)
	if len(paths) > 0 {
		uniqueDIDs := make(map[string]bool)
		for _, path := range paths {
			for _, did := range path {
				uniqueDIDs[did] = true
			}
		}

		handleMap[targetDID] = handle // we already know this one
		for did := range uniqueDIDs {
			if _, exists := handleMap[did]; exists {
				continue
			}
			resolved, err := deps.resolveDidToHandle(did)
			if err != nil {
				handleMap[did] = did // fallback to DID
			} else {
				handleMap[did] = resolved
			}
		}
	}

	return &checkResult{
		targetDID: targetDID,
		paths:     paths,
		handleMap: handleMap,
	}, nil
}

// listVouchSubjects returns the DIDs that the given repo has vouched for.
func listVouchSubjects(ctx context.Context, client *atclient.APIClient, repo string) ([]string, error) {
	var subjects []string
	var cursor string

	for {
		params := map[string]any{
			"repo":       repo,
			"collection": "dev.atvouch.graph.vouch",
			"limit":      100,
		}
		if cursor != "" {
			params["cursor"] = cursor
		}

		var resp struct {
			Records []struct {
				Value struct {
					Subject string `json:"subject"`
				} `json:"value"`
			} `json:"records"`
			Cursor *string `json:"cursor"`
		}

		if err := client.Get(ctx, "com.atproto.repo.listRecords", params, &resp); err != nil {
			return nil, err
		}

		for _, rec := range resp.Records {
			if rec.Value.Subject != "" {
				subjects = append(subjects, rec.Value.Subject)
			}
		}

		if resp.Cursor == nil || *resp.Cursor == "" {
			break
		}
		cursor = *resp.Cursor
	}

	return subjects, nil
}

// fetchVouchersFromMicrocosm returns DIDs that have vouched for the given target DID.
func fetchVouchersFromMicrocosm(targetDID string) ([]string, error) {
	u := "https://constellation.microcosm.blue/links/distinct-dids?" + url.Values{
		"target":     {targetDID},
		"collection": {"dev.atvouch.graph.vouch"},
		"path":       {".subject"},
	}.Encode()

	req, err := http.NewRequest("GET", u, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Accept", "application/json")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

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

	if resp.StatusCode != 200 {
		return nil, fmt.Errorf("microcosm returned %d: %s", resp.StatusCode, string(body))
	}

	var result struct {
		LinkingDIDs []string `json:"linking_dids"`
	}
	if err := json.Unmarshal(body, &result); err != nil {
		return nil, fmt.Errorf("parsing microcosm response: %w", err)
	}

	return result.LinkingDIDs, nil
}

// slingshotResolveHandle resolves a handle to a DID via slingshot.
func slingshotResolveHandle(handle string) (string, error) {
	u := "https://slingshot.microcosm.blue/xrpc/com.atproto.identity.resolveHandle?" + url.Values{
		"handle": {handle},
	}.Encode()

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

	if resp.StatusCode != 200 {
		return "", fmt.Errorf("slingshot returned %d", resp.StatusCode)
	}

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

// slingshotResolveDidToHandle resolves a DID to a handle via slingshot.
func slingshotResolveDidToHandle(did string) (string, error) {
	u := "https://slingshot.microcosm.blue/xrpc/com.bad-example.identity.resolveMiniDoc?" + url.Values{
		"identifier": {did},
	}.Encode()

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

	if resp.StatusCode != 200 {
		return "", fmt.Errorf("slingshot returned %d", resp.StatusCode)
	}

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

func toSet(items []string) map[string]bool {
	s := make(map[string]bool, len(items))
	for _, item := range items {
		s[item] = true
	}
	return s
}

func listenForCallback(ctx context.Context, res chan url.Values) (int, *http.Server, error) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		return 0, nil, err
	}

	mux := http.NewServeMux()
	server := &http.Server{Handler: mux}

	mux.HandleFunc("/callback", func(w http.ResponseWriter, r *http.Request) {
		res <- r.URL.Query()
		w.Header().Set("Content-Type", "text/html")
		w.WriteHeader(200)
		w.Write([]byte("<h1>Authorized! You can close this tab.</h1>"))
		go server.Shutdown(ctx)
	})

	go func() {
		if err := server.Serve(listener); !errors.Is(err, http.ErrServerClosed) {
			log.Fatal(err)
		}
	}()

	return listener.Addr().(*net.TCPAddr).Port, server, nil
}

func openBrowser(url string) error {
	switch runtime.GOOS {
	case "darwin":
		return exec.Command("open", url).Run()
	case "windows":
		return exec.Command("cmd", "/c", "start", url).Run()
	default:
		return exec.Command("xdg-open", url).Run()
	}
}