package auth

import (
	"context"
	"encoding/json"
	"fmt"
	"net"
	"net/http"
	"os"
	"os/exec"
	"time"

	mcpauth "github.com/modelcontextprotocol/go-sdk/auth"
	mcp "github.com/modelcontextprotocol/go-sdk/mcp"
	"github.com/modelcontextprotocol/go-sdk/oauthex"
	"golang.org/x/oauth2"

	"s1d3sw1ped/robinhood-agentic-mcp/client"
	"s1d3sw1ped/robinhood-agentic-mcp/internal/wire"
)

func oauthIdentity(cfg Config) (name, version string) {
	cfg = cfg.WithDefaults()
	return cfg.Name, cfg.Version
}

func loginOAuth(ctx context.Context, cfg Config) (string, error) {
	cfg = cfg.WithDefaults()
	name, version := oauthIdentity(cfg.WithDefaults())

	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		return "", fmt.Errorf("listen: %w", err)
	}
	defer ln.Close()
	port := ln.Addr().(*net.TCPAddr).Port
	redirect := fmt.Sprintf("http://127.0.0.1:%d/callback", port)

	codeCh := make(chan mcpauth.AuthorizationResult, 1)
	mux := http.NewServeMux()
	mux.HandleFunc("/callback", func(w http.ResponseWriter, r *http.Request) {
		q := r.URL.Query()
		if q.Get("error") != "" {
			http.Error(w, q.Get("error_description"), http.StatusBadRequest)
			select {
			case codeCh <- mcpauth.AuthorizationResult{}:
			default:
			}
			return
		}
		res := mcpauth.AuthorizationResult{Code: q.Get("code"), State: q.Get("state"), Iss: q.Get("iss")}
		_, _ = w.Write([]byte(name + " is signed in. You can close this tab."))
		select {
		case codeCh <- res:
		default:
		}
	})
	srv := &http.Server{Handler: mux}
	go func() { _ = srv.Serve(ln) }()
	defer func() {
		shctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
		defer cancel()
		_ = srv.Shutdown(shctx)
	}()

	var saved TokenSet
	oauthCfg := &mcpauth.AuthorizationCodeHandlerConfig{
		RedirectURL: redirect,
		DynamicClientRegistrationConfig: &mcpauth.DynamicClientRegistrationConfig{
			Metadata: &oauthex.ClientRegistrationMetadata{
				RedirectURIs:            []string{redirect},
				ClientName:              name,
				ApplicationType:         "native",
				TokenEndpointAuthMethod: "none",
				GrantTypes:              []string{"authorization_code", "refresh_token"},
				ResponseTypes:           []string{"code"},
			},
		},
		RequestRefreshToken: true,
		AuthorizationCodeFetcher: func(ctx context.Context, args *mcpauth.AuthorizationArgs) (*mcpauth.AuthorizationResult, error) {
			fmt.Fprintf(os.Stderr, "Open this URL to authorize %s with Robinhood:\n\n  %s\n\n", name, args.URL)
			_ = openBrowser(args.URL)
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case res := <-codeCh:
				if res.Code == "" {
					return nil, fmt.Errorf("oauth callback missing code")
				}
				return &res, nil
			}
		},
		NewTokenSource: func(ctx context.Context, oc *oauth2.Config, tok *oauth2.Token) (oauth2.TokenSource, error) {
			saved = tokenSetFrom(oc, tok, redirect, saved.AccountID)
			_ = WriteTokenSet(cfg.TokenFile, saved)
			return oc.TokenSource(ctx, tok), nil
		},
	}
	handler, err := mcpauth.NewAuthorizationCodeHandler(oauthCfg)
	if err != nil {
		return "", fmt.Errorf("oauth handler: %w", err)
	}
	transport := &mcp.StreamableClientTransport{
		Endpoint:             cfg.URL,
		OAuthHandler:         handler,
		DisableStandaloneSSE: true,
	}
	mcpClient := mcp.NewClient(&mcp.Implementation{Name: name, Version: version}, nil)
	ctx, cancel := context.WithTimeout(ctx, 5*time.Minute)
	defer cancel()
	sess, err := mcpClient.Connect(ctx, transport, nil)
	if err != nil {
		return "", fmt.Errorf("connect robinhood mcp: %w", err)
	}
	defer sess.Close()

	c := &client.Client{URL: cfg.URL, Name: name, Version: version}
	c.AttachSession(sess)
	raw, err := c.Call(ctx, "get_accounts", map[string]any{})
	if err != nil {
		return "", fmt.Errorf("get_accounts: %w", err)
	}
	id, err := accountIDFrom(raw)
	if err != nil {
		return "", err
	}
	saved.AccountID = id
	if ts, err := handler.TokenSource(ctx); err == nil && ts != nil {
		if tok, err := ts.Token(); err == nil {
			saved.AccessToken = tok.AccessToken
			saved.RefreshToken = tok.RefreshToken
			saved.Expiry = tok.Expiry
			saved.TokenType = tok.TokenType
		}
	}
	if err := WriteTokenSet(cfg.TokenFile, saved); err != nil {
		return "", err
	}
	return id, nil
}

func tokenSetFrom(oc *oauth2.Config, tok *oauth2.Token, redirect, accountID string) TokenSet {
	if oc == nil {
		oc = &oauth2.Config{}
	}
	if tok == nil {
		tok = &oauth2.Token{}
	}
	return TokenSet{
		AccessToken:  tok.AccessToken,
		RefreshToken: tok.RefreshToken,
		TokenType:    tok.TokenType,
		Expiry:       tok.Expiry,
		ClientID:     oc.ClientID,
		ClientSecret: oc.ClientSecret,
		AuthURL:      oc.Endpoint.AuthURL,
		TokenURL:     oc.Endpoint.TokenURL,
		RedirectURL:  redirect,
		AccountID:    accountID,
	}
}

func openBrowser(rawURL string) error {
	cmds := [][]string{
		{"xdg-open", rawURL},
		{"gio", "open", rawURL},
		{"open", rawURL},
	}
	for _, c := range cmds {
		if err := exec.Command(c[0], c[1:]...).Start(); err == nil {
			return nil
		}
	}
	return fmt.Errorf("open browser")
}

func accountIDFrom(raw json.RawMessage) (string, error) {
	data := wire.Unwrap(raw)
	type row struct {
		ID             string `json:"id"`
		AccountNumber  string `json:"account_number"`
		AgenticAllowed bool   `json:"agentic_allowed"`
		Agentic        bool   `json:"agentic"`
	}
	var wrap struct {
		Accounts []row `json:"accounts"`
	}
	if err := json.Unmarshal(data, &wrap); err != nil || wrap.Accounts == nil {
		var one row
		if err2 := json.Unmarshal(data, &one); err2 != nil {
			if err != nil {
				return "", fmt.Errorf("parse accounts: %w", err)
			}
			return "", fmt.Errorf("parse accounts")
		}
		wrap.Accounts = []row{one}
	}
	for _, a := range wrap.Accounts {
		id := a.AccountNumber
		if id == "" {
			id = a.ID
		}
		if a.AgenticAllowed || a.Agentic {
			return id, nil
		}
	}
	return "", fmt.Errorf("no agentic account")
}

// ClientToken maps a persisted TokenSet to the fields ConnectSession needs.
func ClientToken(t TokenSet) client.Token {
	return client.Token{
		AccessToken:  t.AccessToken,
		RefreshToken: t.RefreshToken,
		TokenType:    t.TokenType,
		Expiry:       t.Expiry,
		ClientID:     t.ClientID,
		ClientSecret: t.ClientSecret,
		AuthURL:      t.AuthURL,
		TokenURL:     t.TokenURL,
		RedirectURL:  t.RedirectURL,
	}
}