// Package squid renders /etc/edgeguard/squid/squid.conf from
// forward_proxy_acls and reloads squid.service. Cache directory
// + in-memory cache are hard-coded sensible defaults; the operator
// scope is just "what can pass through the proxy".
package squid

import (
	"bytes"
	"context"
	_ "embed"
	"fmt"
	"os"
	"path/filepath"
	"text/template"

	"github.com/jackc/pgx/v5/pgxpool"

	"git.netcell-it.de/projekte/edgeguard-native/internal/configgen"
	"git.netcell-it.de/projekte/edgeguard-native/internal/models"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/forwardproxy"
)

const (
	confPath   = "/etc/edgeguard/squid/squid.conf"
	listenPort = 3128
)

//go:embed squid.cfg.tpl
var cfgTpl string

var tpl = template.Must(template.New("squid").Parse(cfgTpl))

type View struct {
	ListenPort int
	ACLs       []models.ForwardProxyACL
}

type Generator struct {
	Pool       *pgxpool.Pool
	Repo       *forwardproxy.Repo
	SkipReload bool
}

func New(pool *pgxpool.Pool) *Generator {
	return &Generator{Pool: pool, Repo: forwardproxy.New(pool)}
}

func (g *Generator) Name() string { return "squid" }

func (g *Generator) Render(ctx context.Context) error {
	acls, err := g.Repo.List(ctx)
	if err != nil {
		return fmt.Errorf("list acls: %w", err)
	}
	view := View{ListenPort: listenPort, ACLs: acls}
	var body bytes.Buffer
	if err := tpl.Execute(&body, view); err != nil {
		return fmt.Errorf("template: %w", err)
	}
	if err := os.MkdirAll(filepath.Dir(confPath), 0o755); err != nil {
		return fmt.Errorf("mkdir: %w", err)
	}
	tmp := confPath + ".tmp"
	if err := os.WriteFile(tmp, body.Bytes(), 0o644); err != nil {
		return fmt.Errorf("write %s: %w", tmp, err)
	}
	if err := os.Rename(tmp, confPath); err != nil {
		return fmt.Errorf("rename: %w", err)
	}
	if err := ensureDistroSymlink(); err != nil {
		return fmt.Errorf("symlink: %w", err)
	}
	if g.SkipReload {
		return nil
	}
	return configgen.ReloadService("squid")
}

// ensureDistroSymlink legt /etc/squid/squid.conf als Symlink auf
// unsere managed conf an. Squid systemd-Unit liest die Distro-Datei;
// ohne Symlink driftet der edgeguard-Renderer und der laufende
// Daemon auseinander (gleicher Bug-Pattern wie wg-quick).
// Existing real file (Distro-Default) wird nach .distro-bak verschoben,
// nicht gelöscht.
func ensureDistroSymlink() error {
	const link = "/etc/squid/squid.conf"
	if cur, err := os.Readlink(link); err == nil && cur == confPath {
		return nil
	}
	if _, err := os.Stat(link); err == nil {
		_ = os.Rename(link, link+".distro-bak")
	}
	return os.Symlink(confPath, link)
}