package credhelper

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"time"
)

// Device authorization API types

type DeviceCodeRequest struct {
	DeviceName string `json:"device_name"`
}

type DeviceCodeResponse struct {
	DeviceCode      string `json:"device_code"`
	UserCode        string `json:"user_code"`
	VerificationURI string `json:"verification_uri"`
	ExpiresIn       int    `json:"expires_in"`
	Interval        int    `json:"interval"`
}

type DeviceTokenRequest struct {
	DeviceCode string `json:"device_code"`
}

type DeviceTokenResponse struct {
	DeviceSecret string `json:"device_secret,omitempty"`
	Handle       string `json:"handle,omitempty"`
	DID          string `json:"did,omitempty"`
	Error        string `json:"error,omitempty"`
}

// AuthErrorResponse is the JSON error response from /auth/token
type AuthErrorResponse struct {
	Error    string `json:"error"`
	Message  string `json:"message"`
	LoginURL string `json:"login_url,omitempty"`
}

// ValidationResult represents the result of credential validation
type ValidationResult struct {
	Valid               bool
	OAuthSessionExpired bool
	LoginURL            string
}

// requestDeviceCode requests a device code from the AppView.
// Returns the code response and resolved AppView URL.
// Does not print anything — the caller controls UX.
func requestDeviceCode(serverURL string) (*DeviceCodeResponse, string, error) {
	appViewURL := buildAppViewURL(serverURL)
	deviceName := hostname()

	reqBody, _ := json.Marshal(DeviceCodeRequest{DeviceName: deviceName})
	resp, err := httpClient().Post(appViewURL+"/auth/device/code", "application/json", bytes.NewReader(reqBody))
	if err != nil {
		return nil, appViewURL, fmt.Errorf("failed to request device code: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, appViewURL, fmt.Errorf("device code request failed: %s", string(body))
	}

	var codeResp DeviceCodeResponse
	if err := json.NewDecoder(resp.Body).Decode(&codeResp); err != nil {
		return nil, appViewURL, fmt.Errorf("failed to decode device code response: %w", err)
	}

	return &codeResp, appViewURL, nil
}

// pollDeviceToken polls the token endpoint until authorization completes.
// Does not print anything — the caller controls UX.
// Returns the account on success, or an error on timeout/failure.
func pollDeviceToken(appViewURL string, codeResp *DeviceCodeResponse) (*Account, error) {
	pollInterval := time.Duration(codeResp.Interval) * time.Second
	timeout := time.Duration(codeResp.ExpiresIn) * time.Second
	deadline := time.Now().Add(timeout)

	for time.Now().Before(deadline) {
		time.Sleep(pollInterval)

		tokenReqBody, _ := json.Marshal(DeviceTokenRequest{DeviceCode: codeResp.DeviceCode})
		tokenResp, err := httpClient().Post(appViewURL+"/auth/device/token", "application/json", bytes.NewReader(tokenReqBody))
		if err != nil {
			continue
		}

		var tokenResult DeviceTokenResponse
		if err := json.NewDecoder(tokenResp.Body).Decode(&tokenResult); err != nil {
			tokenResp.Body.Close()
			continue
		}
		tokenResp.Body.Close()

		if tokenResult.Error == "authorization_pending" {
			continue
		}

		if tokenResult.Error != "" {
			return nil, fmt.Errorf("authorization failed: %s", tokenResult.Error)
		}

		return &Account{
			Handle:       tokenResult.Handle,
			DID:          tokenResult.DID,
			DeviceSecret: tokenResult.DeviceSecret,
		}, nil
	}

	return nil, fmt.Errorf("authorization timed out")
}

// validateCredentials checks if the credentials are still valid by making a test request
func validateCredentials(appViewURL, handle, deviceSecret string) ValidationResult {
	client := httpClientWithTimeout(5*time.Second, nil)

	tokenURL := appViewURL + "/auth/token?service=" + appViewURL

	req, err := http.NewRequest("GET", tokenURL, nil)
	if err != nil {
		return ValidationResult{Valid: false}
	}

	req.SetBasicAuth(handle, deviceSecret)

	resp, err := client.Do(req)
	if err != nil {
		// Network error — assume credentials are valid but server unreachable
		return ValidationResult{Valid: true}
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusOK {
		return ValidationResult{Valid: true}
	}

	if resp.StatusCode == http.StatusUnauthorized {
		body, err := io.ReadAll(resp.Body)
		if err == nil {
			var authErr AuthErrorResponse
			if json.Unmarshal(body, &authErr) == nil && authErr.Error == "oauth_session_expired" {
				return ValidationResult{
					Valid:               false,
					OAuthSessionExpired: true,
					LoginURL:            authErr.LoginURL,
				}
			}
		}
		return ValidationResult{Valid: false}
	}

	// Any other error = assume valid (don't re-auth on server issues)
	return ValidationResult{Valid: true}
}

// hostname returns the machine hostname, or a fallback.
func hostname() string {
	name, err := os.Hostname()
	if err != nil {
		return "Unknown Device"
	}
	return name
}