package licensing

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"strings"
	"time"

	"github.com/rcourtman/pulse-go-rewrite/pkg/securityutil"
)

// LicenseServerClient communicates with the Pulse license server for activation and grant refresh.
type LicenseServerClient struct {
	baseURL    string
	httpClient *http.Client
	initErr    error
}

// CheckoutSessionResult is the canonical purchase-fulfillment response returned
// by the commercial checkout session endpoint.
type CheckoutSessionResult struct {
	Status              string `json:"status"`
	Message             string `json:"message,omitempty"`
	CheckoutStatus      string `json:"checkout_status,omitempty"`
	PaymentStatus       string `json:"payment_status,omitempty"`
	PortalHandoffID     string `json:"portal_handoff_id,omitempty"`
	PurchaseReturnJTI   string `json:"purchase_return_jti,omitempty"`
	LicenseID           string `json:"license_id,omitempty"`
	ActivationKey       string `json:"activation_key,omitempty"`
	ActivationKeyPrefix string `json:"activation_key_prefix,omitempty"`
	OwnerEmail          string `json:"owner_email,omitempty"`
	Tier                string `json:"tier,omitempty"`
	PlanKey             string `json:"plan_key,omitempty"`
}

// CheckoutPortalHandoffRequest is the canonical server-owned request for a
// Pulse Account portal bootstrap record that hides commercial flow state from
// the browser.
type CheckoutPortalHandoffRequest struct {
	Feature           string `json:"feature,omitempty"`
	SuccessURL        string `json:"success_url"`
	CancelURL         string `json:"cancel_url"`
	PurchaseReturnJTI string `json:"purchase_return_jti"`
}

// CheckoutPortalHandoffResponse is the canonical opaque portal handoff used to
// bootstrap the hosted Pulse Account billing flow without exposing the bound
// checkout intent to the browser.
type CheckoutPortalHandoffResponse struct {
	PortalHandoffID string `json:"portal_handoff_id"`
	Feature         string `json:"feature,omitempty"`
	ExpiresAt       int64  `json:"expires_at,omitempty"`
}

// NewLicenseServerClient creates a client for the license server.
// The base URL defaults to DefaultLicenseServerURL. The PULSE_LICENSE_SERVER_URL
// env var override is only allowed in non-release builds.
func NewLicenseServerClient(baseURL string) *LicenseServerClient {
	if baseURL == "" && allowLicenseServerURLEnvOverride() {
		baseURL = os.Getenv("PULSE_LICENSE_SERVER_URL")
	}
	if baseURL == "" {
		baseURL = DefaultLicenseServerURL
	}

	var initErr error
	normalizedBaseURL, err := securityutil.NormalizeSecureHTTPBaseURL(baseURL)
	if err != nil {
		initErr = fmt.Errorf("license server URL %q is invalid: %w", baseURL, err)
		baseURL = ""
	} else {
		baseURL = normalizedBaseURL.String()
	}

	return &LicenseServerClient{
		baseURL: baseURL,
		httpClient: securityutil.NewRestrictedOutboundHTTPClient(15*time.Second, securityutil.RestrictedOutboundHTTPOptions{
			AllowedSchemes: []string{"http", "https"},
			AllowLoopback:  true,
		}),
		initErr: initErr,
	}
}

func (c *LicenseServerClient) ready() error {
	if c == nil {
		return fmt.Errorf("license server client is nil")
	}
	if c.initErr != nil {
		return c.initErr
	}
	if strings.TrimSpace(c.baseURL) == "" {
		return fmt.Errorf("license server URL is unavailable")
	}
	if c.httpClient == nil {
		return fmt.Errorf("license server HTTP client is unavailable")
	}
	return nil
}

// Activate calls the license server to create an installation and receive a relay grant.
func (c *LicenseServerClient) Activate(ctx context.Context, req ActivateInstallationRequest) (*ActivateInstallationResponse, error) {
	if err := c.ready(); err != nil {
		return nil, err
	}

	body, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("marshal activate request: %w", err)
	}

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/v1/activate", bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("create activate request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("Idempotency-Key", generateIdempotencyKey())

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("activate request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		return nil, c.parseError(resp)
	}

	var result ActivateInstallationResponse
	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode activate response: %w", err)
	}
	return &result, nil
}

// ExchangeLegacyLicense converts a legacy v5 JWT-style license into a v6 activation.
// The response shape matches normal activation so the runtime can persist activation
// state and start using grant refresh immediately.
func (c *LicenseServerClient) ExchangeLegacyLicense(ctx context.Context, req ExchangeLegacyLicenseRequest) (*ActivateInstallationResponse, error) {
	if err := c.ready(); err != nil {
		return nil, err
	}

	body, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("marshal exchange request: %w", err)
	}

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/v1/licenses/exchange", bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("create exchange request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("Idempotency-Key", generateIdempotencyKey())

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("exchange request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		return nil, c.parseError(resp)
	}

	var result ActivateInstallationResponse
	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode exchange response: %w", err)
	}
	return &result, nil
}

// RefreshGrant calls the license server to refresh a relay grant.
// The installationToken is sent as a Bearer token in the Authorization header.
func (c *LicenseServerClient) RefreshGrant(ctx context.Context, installationID, installationToken string, req RefreshGrantRequest) (*RefreshGrantResponse, error) {
	if err := c.ready(); err != nil {
		return nil, err
	}

	body, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("marshal refresh request: %w", err)
	}

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/v1/grants/refresh", bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("create refresh request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("Authorization", "Bearer "+installationToken)

	// Use a shorter timeout for refresh since it's a background operation.
	refreshClient := *c.httpClient
	refreshClient.Timeout = 10 * time.Second

	resp, err := refreshClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("refresh request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, c.parseError(resp)
	}

	var result RefreshGrantResponse
	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode refresh response: %w", err)
	}
	return &result, nil
}

// GetCheckoutSessionResult resolves a commercial checkout session into its
// authoritative fulfillment payload.
func (c *LicenseServerClient) GetCheckoutSessionResult(ctx context.Context, sessionID string) (*CheckoutSessionResult, error) {
	if err := c.ready(); err != nil {
		return nil, err
	}

	sessionID = strings.TrimSpace(sessionID)
	if sessionID == "" {
		return nil, fmt.Errorf("checkout session id is required")
	}

	httpReq, err := http.NewRequestWithContext(
		ctx,
		http.MethodGet,
		c.baseURL+"/v1/checkout/session?session_id="+url.QueryEscape(sessionID),
		nil,
	)
	if err != nil {
		return nil, fmt.Errorf("create checkout session result request: %w", err)
	}
	httpReq.Header.Set("Accept", "application/json")

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("checkout session result request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, c.parseError(resp)
	}

	var result CheckoutSessionResult
	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode checkout session result response: %w", err)
	}
	return &result, nil
}

// CreateCheckoutPortalHandoff stores a server-owned Pulse Account bootstrap
// record and returns an opaque portal_handoff_id for browser navigation.
func (c *LicenseServerClient) CreateCheckoutPortalHandoff(ctx context.Context, req CheckoutPortalHandoffRequest) (*CheckoutPortalHandoffResponse, error) {
	if err := c.ready(); err != nil {
		return nil, err
	}

	body, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("marshal checkout portal handoff request: %w", err)
	}

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/v1/checkout/portal-handoff", bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("create checkout portal handoff request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("Accept", "application/json")

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("checkout portal handoff request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		return nil, c.parseError(resp)
	}

	var result CheckoutPortalHandoffResponse
	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode checkout portal handoff response: %w", err)
	}
	return &result, nil
}

// FetchRevocations polls the revocation feed for events after the given sequence number.
// The feedToken authenticates access to the revocation feed.
func (c *LicenseServerClient) FetchRevocations(ctx context.Context, feedToken string, sinceSeq int64, limit int) (*RevocationFeedResponse, error) {
	if err := c.ready(); err != nil {
		return nil, err
	}

	if limit <= 0 {
		limit = 500
	}

	url := fmt.Sprintf("%s/v1/revocations?since_seq=%d&limit=%d", c.baseURL, sinceSeq, limit)
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, fmt.Errorf("create revocations request: %w", err)
	}
	httpReq.Header.Set("Authorization", "Bearer "+feedToken)

	// Use a shorter timeout for polling.
	pollClient := *c.httpClient
	pollClient.Timeout = 10 * time.Second

	resp, err := pollClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("revocations request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, c.parseError(resp)
	}

	var result RevocationFeedResponse
	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode revocations response: %w", err)
	}
	return &result, nil
}

// BaseURL returns the configured license server base URL.
func (c *LicenseServerClient) BaseURL() string {
	return c.baseURL
}

// generateIdempotencyKey creates a unique key for idempotent requests.
func generateIdempotencyKey() string {
	b := make([]byte, 16)
	_, _ = rand.Read(b)
	return hex.EncodeToString(b)
}

// parseError reads an error response from the license server and returns a structured LicenseServerError.
func (c *LicenseServerClient) parseError(resp *http.Response) error {
	body, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<16))

	apiErr := &LicenseServerError{
		StatusCode: resp.StatusCode,
		Code:       fmt.Sprintf("http_%d", resp.StatusCode),
		Message:    http.StatusText(resp.StatusCode),
	}

	// Try to parse structured error response from the license server.
	if len(body) > 0 {
		var parsed struct {
			Code       string `json:"code"`
			LegacyCode string `json:"error"`
			Message    string `json:"message"`
			Retryable  bool   `json:"retryable"`
		}
		if json.Unmarshal(body, &parsed) == nil {
			code := strings.TrimSpace(parsed.Code)
			if code == "" {
				code = strings.TrimSpace(parsed.LegacyCode)
			}
			if code != "" {
				apiErr.Code = code
				if strings.TrimSpace(parsed.Message) != "" {
					apiErr.Message = parsed.Message
				}
				apiErr.Retryable = parsed.Retryable
			}
		}
	}

	// Mark server errors as retryable by default.
	if resp.StatusCode >= 500 {
		apiErr.Retryable = true
	}

	return apiErr
}