package credhelper

import (
	"encoding/json"
	"fmt"
	"os"
	"strings"

	"github.com/spf13/cobra"
)

// Credentials represents docker credentials (Docker credential helper protocol)
type Credentials struct {
	ServerURL string `json:"ServerURL,omitempty"`
	Username  string `json:"Username,omitempty"`
	Secret    string `json:"Secret,omitempty"`
}

func newGetCmd() *cobra.Command {
	return &cobra.Command{
		Use:    "get",
		Short:  "Get credentials for a registry (Docker protocol)",
		Hidden: true,
		RunE:   runGet,
	}
}

func newStoreCmd() *cobra.Command {
	return &cobra.Command{
		Use:    "store",
		Short:  "Store credentials (Docker protocol)",
		Hidden: true,
		RunE:   runStore,
	}
}

func newEraseCmd() *cobra.Command {
	return &cobra.Command{
		Use:    "erase",
		Short:  "Erase credentials (Docker protocol)",
		Hidden: true,
		RunE:   runErase,
	}
}

func newListCmd() *cobra.Command {
	return &cobra.Command{
		Use:    "list",
		Short:  "List all credentials (Docker protocol extension)",
		Hidden: true,
		RunE:   runList,
	}
}

func runGet(cmd *cobra.Command, args []string) error {
	// If stdin is a terminal, the user ran this directly (not Docker calling us)
	if isTerminal(os.Stdin) {
		fmt.Fprintf(os.Stderr, "The 'get' command is part of the Docker credential helper protocol.\n")
		fmt.Fprintf(os.Stderr, "It should not be run directly.\n\n")
		fmt.Fprintf(os.Stderr, "To authenticate with a registry, run:\n")
		fmt.Fprintf(os.Stderr, "  %s login\n\n", cfg.BinaryName)
		fmt.Fprintf(os.Stderr, "To check your accounts:\n")
		fmt.Fprintf(os.Stderr, "  %s status\n", cfg.BinaryName)
		return fmt.Errorf("not a pipe")
	}

	// Docker sends the server URL as a plain string on stdin (not JSON)
	var serverURL string
	if _, err := fmt.Fscanln(os.Stdin, &serverURL); err != nil {
		return fmt.Errorf("reading server URL: %w", err)
	}

	appViewURL := buildAppViewURL(serverURL)

	// `get` can rewrite the config (DID backfill, or removing an account whose
	// credentials no longer validate), so it must not proceed on a config it
	// failed to parse — the empty fallback would be saved over the real one.
	// Returned, not printed: Run's top-level handler already prints it.
	sc, err := loadConfigForWrite()
	if err != nil {
		return err
	}

	acct, err := sc.resolveAccount(appViewURL, serverURL)
	if err != nil {
		return err
	}

	// Validate credentials
	result := validateCredentials(appViewURL, acct.Handle, acct.DeviceSecret)
	if !result.Valid {
		if result.OAuthSessionExpired {
			loginURL := result.LoginURL
			if loginURL == "" {
				loginURL = appViewURL + "/auth/oauth/login"
			}
			fmt.Fprintf(os.Stderr, "OAuth session expired for %s.\n", acct.Handle)
			fmt.Fprintf(os.Stderr, "Please visit: %s\n", loginURL)
			fmt.Fprintf(os.Stderr, "Then retry your docker command.\n")
			return fmt.Errorf("oauth session expired")
		}

		// Generic auth failure — remove the bad account
		fmt.Fprintf(os.Stderr, "Credentials for %s are invalid.\n", acct.Handle)
		fmt.Fprintf(os.Stderr, "Run: %s login\n", cfg.BinaryName)
		sc.removeAccount(appViewURL, acct.key())
		sc.save() //nolint:errcheck
		return fmt.Errorf("invalid credentials")
	}

	// Credentials are valid. If this account is still keyed by handle (e.g.
	// created via Docker `store`, which has no DID), backfill its DID by
	// resolving the handle and re-key it. Best-effort: resolution failure is
	// non-fatal and the secret works regardless.
	if acct.DID == "" {
		if did, resolveErr := resolveHandleDID(acct.Handle); resolveErr == nil {
			if reg := sc.findRegistry(appViewURL); reg != nil {
				reg.rekey(acct, did)
				sc.save() //nolint:errcheck
			}
		}
	}

	// Check for updates (cached, non-blocking)
	checkAndNotifyUpdate()

	// Return credentials for Docker
	creds := Credentials{
		ServerURL: serverURL,
		Username:  acct.Handle,
		Secret:    acct.DeviceSecret,
	}

	return json.NewEncoder(os.Stdout).Encode(creds)
}

func runStore(cmd *cobra.Command, args []string) error {
	var creds Credentials
	if err := json.NewDecoder(os.Stdin).Decode(&creds); err != nil {
		return fmt.Errorf("decoding credentials: %w", err)
	}

	// Only store if the secret looks like one of our device secrets
	if !strings.HasPrefix(creds.Secret, cfg.SecretPrefix) {
		// Not our device secret — ignore (e.g., docker login with app-password)
		return nil
	}

	appViewURL := buildAppViewURL(creds.ServerURL)

	// Refuse to write when the existing config couldn't be read. Warning and
	// continuing would save the empty fallback config, replacing every stored
	// account with just this one. That is the downgrade path: an older build
	// cannot parse a v3 file, so the first `docker login` would wipe it.
	// Returned, not printed: Run's top-level handler already prints it.
	sc, err := loadConfigForWrite()
	if err != nil {
		return err
	}

	// Docker's store protocol only supplies {username, secret} — no DID. Resolve
	// the handle to its DID (best-effort) so the account keys by the stable DID.
	// addAccount/upsert preserves any existing DID rather than blanking it.
	did, _ := resolveHandleDID(creds.Username)
	sc.addAccount(appViewURL, &Account{
		Handle:       creds.Username,
		DID:          did,
		DeviceSecret: creds.Secret,
	})

	return sc.save()
}

func runErase(cmd *cobra.Command, args []string) error {
	var serverURL string
	if _, err := fmt.Fscanln(os.Stdin, &serverURL); err != nil {
		return fmt.Errorf("reading server URL: %w", err)
	}

	appViewURL := buildAppViewURL(serverURL)

	// Erase writes, so an unreadable config means we do nothing rather than
	// save the empty fallback over it. Reported as success: Docker surfaces a
	// failing `logout` as a hard error, and there is nothing the user can act on.
	sc, err := loadConfigForWrite()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Warning: %v\n", err)
		return nil
	}

	reg := sc.findRegistry(appViewURL)
	if reg == nil {
		return nil
	}

	// Erase the active account (or sole account)
	handle := reg.Active
	if handle == "" && len(reg.Accounts) == 1 {
		for h := range reg.Accounts {
			handle = h
		}
	}
	if handle == "" {
		return nil
	}

	sc.removeAccount(appViewURL, handle)
	return sc.save()
}

func runList(cmd *cobra.Command, args []string) error {
	sc, err := loadConfig()
	if err != nil {
		// Return empty object
		fmt.Println("{}")
		return nil
	}

	// Docker list protocol: {"ServerURL": "Username", ...}
	// Report exactly one username per registry: the active account (or the
	// sole account if none is explicitly active), matching what `get` hands
	// Docker via resolveAccount. The map is keyed by DID, but the protocol
	// value must be the handle/username, so read acct.Handle.
	result := make(map[string]string)
	for url, reg := range sc.Registries {
		// Strip scheme for Docker compatibility
		host := strings.TrimPrefix(url, "https://")
		host = strings.TrimPrefix(host, "http://")

		acct := reg.activeAccount()
		if acct == nil {
			continue
		}
		result[host] = acct.Handle
	}

	return json.NewEncoder(os.Stdout).Encode(result)
}

// checkAndNotifyUpdate checks for updates in the background and notifies the user
func checkAndNotifyUpdate() {
	cache := loadUpdateCheckCache()
	if cache != nil && cache.Current == cfg.Version {
		// Cache is fresh and for current version
		if isNewerVersion(cache.Latest, cfg.Version) {
			fmt.Fprintf(os.Stderr, "\nUpdate available: %s (current: %s)\n", cache.Latest, cfg.Version)
			fmt.Fprintf(os.Stderr, "Run: %s update\n\n", cfg.BinaryName)
		}
		// Check if cache is still fresh (24h)
		if cache.CheckedAt.Add(updateCheckCacheTTL).After(timeNow()) {
			return
		}
	}

	latest, err := fetchLatestVersion()
	if err != nil {
		return // Silently fail
	}

	saveUpdateCheckCache(&UpdateCheckCache{
		CheckedAt: timeNow(),
		Latest:    latest,
		Current:   cfg.Version,
	})

	if isNewerVersion(latest, cfg.Version) {
		fmt.Fprintf(os.Stderr, "\nUpdate available: %s (current: %s)\n", latest, cfg.Version)
		fmt.Fprintf(os.Stderr, "Run: %s update\n\n", cfg.BinaryName)
	}
}