// Package certrenewer encapsulates the "find expiring certs +
// re-issue them via Let's Encrypt + reload haproxy" pipeline so the
// scheduler and the handler share the exact same write path.
//
// Scope deliberately narrow:
//   - Only Let's Encrypt-issued rows are renewed (manually-uploaded
//     PEMs stay untouched — operator owns the lifecycle).
//   - Re-issue happens when not_after - now < threshold (default
//     30 days). LE recommends 30; certbot defaults to 30.
//   - On error, the row's last_error is set; the schedule retries
//     on the next tick, so a transient ACME failure self-heals.
package certrenewer

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"os/exec"
	"time"

	"git.netcell-it.de/projekte/edgeguard-native/internal/models"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/certstore"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/tlscerts"
)

// Issuer is the contract acme.Service implements (Issue is also
// used for renewal — LE doesn't distinguish; a fresh cert with the
// same Common-Name supersedes the old one).
type Issuer interface {
	Issue(domain string) (cert, chain, key string, err error)
}

type Service struct {
	Repo      *tlscerts.Repo
	Issuer    Issuer
	CertDir   string
	Threshold time.Duration

	// Logger lets the scheduler attach its slog handler. If nil,
	// the package uses slog.Default.
	Logger *slog.Logger
}

func New(repo *tlscerts.Repo, issuer Issuer, certDir string, threshold time.Duration) *Service {
	if threshold == 0 {
		threshold = 30 * 24 * time.Hour
	}
	return &Service{
		Repo:      repo,
		Issuer:    issuer,
		CertDir:   certDir,
		Threshold: threshold,
	}
}

func (s *Service) log() *slog.Logger {
	if s.Logger != nil {
		return s.Logger
	}
	return slog.Default()
}

// Result counts what one Run pass did so the scheduler can log /
// surface it.
type Result struct {
	Checked  int
	Renewed  int
	Failed   int
	Skipped  int
}

// Run scans tls_certs for LE-issued rows that expire within the
// threshold, re-issues each via the Issuer, writes the new PEM and
// triggers an HAProxy reload at the end if anything changed. Errors
// per cert are logged and recorded in tls_certs.last_error but do
// not abort the loop.
func (s *Service) Run(ctx context.Context) (Result, error) {
	if s.Issuer == nil {
		return Result{}, errors.New("certrenewer: Issuer is nil — ACME-Email noch nicht im Setup gesetzt?")
	}
	rows, err := s.Repo.ListExpiringSoon(ctx, s.Threshold)
	if err != nil {
		return Result{}, fmt.Errorf("list expiring: %w", err)
	}
	res := Result{Checked: len(rows)}
	anyRenewed := false
	for _, row := range rows {
		if row.Issuer != "letsencrypt" {
			res.Skipped++
			s.log().Debug("certrenewer: skip non-LE cert", "domain", row.Domain, "issuer", row.Issuer)
			continue
		}
		s.log().Info("certrenewer: renewing", "domain", row.Domain, "expires", row.NotAfter)
		certPEM, chainPEM, keyPEM, err := s.Issuer.Issue(row.Domain)
		if err != nil {
			res.Failed++
			s.log().Error("certrenewer: issue failed", "domain", row.Domain, "error", err)
			_ = s.Repo.MarkError(ctx, row.Domain, err.Error())
			continue
		}
		info, err := certstore.Parse(certPEM)
		if err != nil {
			res.Failed++
			_ = s.Repo.MarkError(ctx, row.Domain, "parse: "+err.Error())
			continue
		}
		path, err := certstore.WriteCombined(s.CertDir, row.Domain, certPEM, chainPEM, keyPEM)
		if err != nil {
			res.Failed++
			_ = s.Repo.MarkError(ctx, row.Domain, "write: "+err.Error())
			continue
		}
		now := time.Now()
		if _, err := s.Repo.Upsert(ctx, models.TLSCert{
			Domain:        row.Domain,
			Issuer:        "letsencrypt",
			Status:        "active",
			CertPath:      &path,
			KeyPath:       &path,
			NotBefore:     &info.NotBefore,
			NotAfter:      &info.NotAfter,
			LastRenewedAt: &now,
		}); err != nil {
			res.Failed++
			s.log().Error("certrenewer: upsert failed", "domain", row.Domain, "error", err)
			continue
		}
		res.Renewed++
		anyRenewed = true
	}
	if anyRenewed {
		if err := reloadHAProxy(); err != nil {
			s.log().Warn("certrenewer: haproxy reload failed", "error", err)
		} else {
			s.log().Info("certrenewer: haproxy reloaded")
		}
	}
	return res, nil
}

func reloadHAProxy() error {
	return exec.Command("sudo", "-n", "/usr/bin/systemctl", "reload", "haproxy.service").Run()
}