package acme

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"time"

	"github.com/shankar0123/certctl/internal/connector/issuer"
)

// Config represents the ACME issuer connector configuration.
type Config struct {
	DirectoryURL string `json:"directory_url"`
	Email        string `json:"email"`
	EABKid       string `json:"eab_kid,omitempty"`
	EABHmac      string `json:"eab_hmac,omitempty"`
}

// Connector implements the issuer.Connector interface for ACME-compatible CAs.
// This is a stub implementation that demonstrates the structure; actual ACME protocol
// implementation will use a proper ACME library (e.g., golang.org/x/crypto/acme).
type Connector struct {
	config *Config
	logger *slog.Logger
	client *http.Client
}

// New creates a new ACME connector with the given configuration and logger.
func New(config *Config, logger *slog.Logger) *Connector {
	return &Connector{
		config: config,
		logger: logger,
		client: &http.Client{Timeout: 30 * time.Second},
	}
}

// ValidateConfig checks that the ACME directory URL is reachable and valid.
// It performs a HEAD request to the directory URL to verify connectivity.
func (c *Connector) ValidateConfig(ctx context.Context, rawConfig json.RawMessage) error {
	var cfg Config
	if err := json.Unmarshal(rawConfig, &cfg); err != nil {
		return fmt.Errorf("invalid ACME config: %w", err)
	}

	if cfg.DirectoryURL == "" {
		return fmt.Errorf("ACME directory_url is required")
	}

	if cfg.Email == "" {
		return fmt.Errorf("ACME email is required")
	}

	c.logger.Info("validating ACME configuration", "directory_url", cfg.DirectoryURL)

	// Verify that the directory URL is reachable
	req, err := http.NewRequestWithContext(ctx, http.MethodHead, cfg.DirectoryURL, nil)
	if err != nil {
		return fmt.Errorf("failed to create request: %w", err)
	}

	resp, err := c.client.Do(req)
	if err != nil {
		return fmt.Errorf("failed to reach ACME directory: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("ACME directory returned status %d", resp.StatusCode)
	}

	c.config = &cfg
	c.logger.Info("ACME configuration validated")
	return nil
}

// IssueCertificate submits a certificate issuance request to the ACME CA.
//
// The flow for ACME is:
// 1. Create a new order with the CA, specifying the identifiers (SANs + CN)
// 2. The CA returns authorization challenges (DNS, HTTP, etc.)
// 3. Solve the challenges (stub: in production, the agent or external solver handles this)
// 4. Finalize the order by submitting the CSR
// 5. Download the issued certificate and chain
//
// TODO: Implement actual ACME protocol using golang.org/x/crypto/acme.
// This stub documents the expected flow but doesn't execute it.
func (c *Connector) IssueCertificate(ctx context.Context, request issuer.IssuanceRequest) (*issuer.IssuanceResult, error) {
	c.logger.Info("processing ACME issuance request",
		"common_name", request.CommonName,
		"san_count", len(request.SANs))

	// TODO: Implement ACME order creation.
	// For now, return a stub response to demonstrate the interface.
	// In production:
	//   1. Connect to the ACME directory
	//   2. Create a new order with identifiers from CommonName and SANs
	//   3. Get authorization challenges
	//   4. Wait for challenge completion (agent/solver will handle)
	//   5. Submit CSR to finalize order
	//   6. Retrieve issued certificate and chain

	c.logger.Warn("ACME issuance not yet implemented", "common_name", request.CommonName)

	// Stub: Return a placeholder result
	return &issuer.IssuanceResult{
		CertPEM:   "-----BEGIN CERTIFICATE-----\n(stub)\n-----END CERTIFICATE-----\n",
		ChainPEM:  "-----BEGIN CERTIFICATE-----\n(stub chain)\n-----END CERTIFICATE-----\n",
		Serial:    "stub-serial-123456",
		NotBefore: time.Now(),
		NotAfter:  time.Now().AddDate(0, 0, 90),
		OrderID:   "stub-order-id",
	}, nil
}

// RenewCertificate renews an existing certificate by submitting a new ACME order.
// The process is identical to IssueCertificate but uses the existing CSR from the previous certificate.
//
// TODO: Implement actual ACME protocol using golang.org/x/crypto/acme.
func (c *Connector) RenewCertificate(ctx context.Context, request issuer.RenewalRequest) (*issuer.IssuanceResult, error) {
	c.logger.Info("processing ACME renewal request",
		"common_name", request.CommonName,
		"san_count", len(request.SANs))

	// TODO: Implement ACME renewal.
	// In production:
	//   1. Create a new order with the same identifiers
	//   2. Obtain and solve authorization challenges
	//   3. Submit the CSR (from request.CSRPEM)
	//   4. Retrieve the issued certificate and chain

	c.logger.Warn("ACME renewal not yet implemented", "common_name", request.CommonName)

	// Stub: Return a placeholder result
	return &issuer.IssuanceResult{
		CertPEM:   "-----BEGIN CERTIFICATE-----\n(stub renewed)\n-----END CERTIFICATE-----\n",
		ChainPEM:  "-----BEGIN CERTIFICATE-----\n(stub chain)\n-----END CERTIFICATE-----\n",
		Serial:    "stub-serial-renewal-123456",
		NotBefore: time.Now(),
		NotAfter:  time.Now().AddDate(0, 0, 90),
		OrderID:   "stub-order-renewal-id",
	}, nil
}

// RevokeCertificate revokes a certificate at the ACME CA.
// The CA will no longer consider the certificate valid.
//
// TODO: Implement revocation via ACME protocol.
func (c *Connector) RevokeCertificate(ctx context.Context, request issuer.RevocationRequest) error {
	c.logger.Info("processing ACME revocation request", "serial", request.Serial)

	// TODO: Implement ACME revocation.
	// In production:
	//   1. Retrieve the certificate PEM
	//   2. Post revocation request to CA's revocation endpoint
	//   3. Provide reason if given

	c.logger.Warn("ACME revocation not yet implemented", "serial", request.Serial)
	return nil
}

// GetOrderStatus retrieves the current status of an ACME order.
// This is useful for polling the status of pending issuance or renewal orders.
//
// TODO: Implement order status polling.
func (c *Connector) GetOrderStatus(ctx context.Context, orderID string) (*issuer.OrderStatus, error) {
	c.logger.Info("fetching ACME order status", "order_id", orderID)

	// TODO: Implement ACME order status polling.
	// In production:
	//   1. Connect to the ACME directory
	//   2. Fetch order status by orderID
	//   3. Return current status, message, and any issued certificate material

	c.logger.Warn("ACME order status polling not yet implemented", "order_id", orderID)

	// Stub: Return a placeholder status
	return &issuer.OrderStatus{
		OrderID:   orderID,
		Status:    "processing",
		Message:   nil,
		UpdatedAt: time.Now(),
	}, nil
}