package certbot

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"
)

// CertStatus represents the current state of a TLS certificate.
type CertStatus struct {
	Exists    bool      `json:"exists"`
	Domain    string    `json:"domain"`
	Expiry    time.Time `json:"expiry,omitempty"`
	CertPath  string    `json:"certPath,omitempty"`
	KeyPath   string    `json:"keyPath,omitempty"`
	DaysLeft  int       `json:"daysLeft,omitempty"`
	IssuerCN  string    `json:"issuerCN,omitempty"`
}

// Manager handles TLS certificate provisioning via certbot.
type Manager struct {
	credsPath string // path to cloudflare credentials ini file
}

// NewManager creates a new certbot manager.
// credsPath is the path to the Cloudflare API credentials file used for DNS-01 challenges.
func NewManager(credsPath string) *Manager {
	if credsPath == "" {
		credsPath = "/etc/letsencrypt/cloudflare.ini"
	}
	return &Manager{credsPath: credsPath}
}

// EnsureCredentials writes the Cloudflare API token to the credentials file
// for certbot's DNS-01 challenge. Safe to call repeatedly.
func (m *Manager) EnsureCredentials(apiToken string) error {
	if apiToken == "" {
		return fmt.Errorf("cloudflare API token is empty")
	}
	dir := filepath.Dir(m.credsPath)
	if err := os.MkdirAll(dir, 0700); err != nil {
		return fmt.Errorf("create credentials dir: %w", err)
	}
	content := fmt.Sprintf("dns_cloudflare_api_token = %s\n", apiToken)
	if err := os.WriteFile(m.credsPath, []byte(content), 0600); err != nil {
		return fmt.Errorf("write credentials: %w", err)
	}
	return nil
}

// Provision requests a new TLS certificate for the given domain using DNS-01 via Cloudflare.
// A deploy hook builds the combined PEM for HAProxy and reloads HAProxy automatically.
func (m *Manager) Provision(domain, email string) error {
	if domain == "" {
		return fmt.Errorf("domain is required")
	}
	if email == "" {
		return fmt.Errorf("email is required")
	}
	if _, err := os.Stat(m.credsPath); err != nil {
		return fmt.Errorf("cloudflare credentials not found at %s; configure the Cloudflare API token first", m.credsPath)
	}

	// Deploy hook runs as root (certbot runs via sudo), so it can read the cert files.
	// It builds the combined PEM for HAProxy and reloads the service.
	haproxyPEM := HAProxyCertPath(domain)
	deployHook := fmt.Sprintf(
		"mkdir -p %s && cat %s %s > %s && systemctl reload haproxy 2>/dev/null || true",
		filepath.Dir(haproxyPEM), CertPath(domain), KeyPath(domain), haproxyPEM,
	)

	cmd := exec.Command("sudo", "certbot", "certonly",
		"--dns-cloudflare",
		"--dns-cloudflare-credentials", m.credsPath,
		"-d", domain,
		"--non-interactive",
		"--agree-tos",
		"-m", email,
		"--deploy-hook", deployHook,
	)
	out, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("certbot: %w\n%s", err, string(out))
	}
	return nil
}

// Renew renews all certificates managed by certbot.
func (m *Manager) Renew() error {
	cmd := exec.Command("sudo", "certbot", "renew", "--non-interactive")
	out, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("certbot renew: %w\n%s", err, string(out))
	}
	return nil
}

// GetStatus returns the TLS certificate status for a domain.
// Reads the HAProxy combined PEM (which we own) rather than certbot's root-owned files.
func (m *Manager) GetStatus(domain string) *CertStatus {
	status := &CertStatus{Domain: domain}

	pemPath := HAProxyCertPath(domain)
	if _, err := os.Stat(pemPath); err != nil {
		return status
	}
	status.Exists = true
	status.CertPath = pemPath
	status.KeyPath = pemPath

	// Parse expiry from the certificate
	cmd := exec.Command("openssl", "x509", "-in", pemPath, "-noout", "-enddate", "-issuer")
	out, err := cmd.Output()
	if err != nil {
		return status
	}

	for line := range strings.SplitSeq(string(out), "\n") {
		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "notAfter=") {
			dateStr := strings.TrimPrefix(line, "notAfter=")
			if t, err := time.Parse("Jan  2 15:04:05 2006 GMT", dateStr); err == nil {
				status.Expiry = t
				status.DaysLeft = int(time.Until(t).Hours() / 24)
			} else if t, err := time.Parse("Jan 2 15:04:05 2006 GMT", dateStr); err == nil {
				status.Expiry = t
				status.DaysLeft = int(time.Until(t).Hours() / 24)
			}
		}
		if strings.HasPrefix(line, "issuer=") {
			status.IssuerCN = strings.TrimPrefix(line, "issuer=")
		}
	}

	return status
}

// CertPath returns the fullchain.pem path for a domain.
func CertPath(domain string) string {
	return fmt.Sprintf("/etc/letsencrypt/live/%s/fullchain.pem", domain)
}

// KeyPath returns the privkey.pem path for a domain.
func KeyPath(domain string) string {
	return fmt.Sprintf("/etc/letsencrypt/live/%s/privkey.pem", domain)
}

// HAProxyCertPath returns the combined PEM path for HAProxy TLS termination.
func HAProxyCertPath(domain string) string {
	return fmt.Sprintf("/etc/haproxy/certs/%s.pem", domain)
}

// BuildHAProxyCert concatenates fullchain.pem + privkey.pem into a single PEM
// file that HAProxy can use for TLS termination.
// Uses sudo to read certbot's root-owned files.
func (m *Manager) BuildHAProxyCert(domain string) error {
	certData, err := exec.Command("sudo", "cat", CertPath(domain)).Output()
	if err != nil {
		return fmt.Errorf("read fullchain: %w", err)
	}
	keyData, err := exec.Command("sudo", "cat", KeyPath(domain)).Output()
	if err != nil {
		return fmt.Errorf("read privkey: %w", err)
	}
	combined := append(certData, keyData...)
	outPath := HAProxyCertPath(domain)
	if err := os.MkdirAll(filepath.Dir(outPath), 0700); err != nil {
		return fmt.Errorf("create haproxy certs dir: %w", err)
	}
	return os.WriteFile(outPath, combined, 0600)
}