package server

import (
	"fmt"
	"log"
	"net"
	"os"
	"os/exec"
	"strings"
	"sync"
)

// ufwManager integrates with the host firewall (ufw) when it is installed and
// active. Opening a forward port in the panel also opens it in ufw; the created
// rules are tracked so they can be listed and revoked from Settings.
//
// ufw requires root, so this only works when the server process can run ufw
// (e.g. running as root). When it cannot, integration is simply inactive.
type ufwManager struct {
	db *DB
	// tunnelPort returns the current direct-tunnel port (0 = tunnel disabled).
	tunnelPort func() int

	mu      sync.Mutex
	lastErr string // last failed ufw command, shown in Settings
}

func newUfwManager(db *DB, tunnelPort func() int) *ufwManager {
	return &ufwManager{db: db, tunnelPort: tunnelPort}
}

// ufwRun runs ufw with a fixed C locale: its output is translated, and we
// match on the English text.
func ufwRun(args ...string) (string, error) {
	cmd := exec.Command("ufw", args...)
	cmd.Env = append(os.Environ(), "LC_ALL=C", "LANG=C", "LANGUAGE=C")
	out, err := cmd.CombinedOutput()
	return strings.TrimSpace(string(out)), err
}

// status reports whether ufw is installed, active, and runnable by this process.
func (u *ufwManager) status() (installed, active, runnable bool) {
	if _, err := exec.LookPath("ufw"); err != nil {
		return false, false, false
	}
	installed = true
	out, err := ufwRun("status")
	if err != nil {
		// Typically a permission error (not root) -> not runnable.
		return true, false, false
	}
	runnable = true
	active = strings.Contains(out, "Status: active")
	return installed, active, runnable
}

// available reports whether we can and should drive ufw now.
func (u *ufwManager) available() bool {
	if !u.db.UfwEnabled() {
		return false
	}
	installed, active, runnable := u.status()
	return installed && active && runnable
}

func (u *ufwManager) setErr(msg string) {
	u.mu.Lock()
	u.lastErr = msg
	u.mu.Unlock()
}

// LastError returns the last failed ufw command ("" when the last one worked).
func (u *ufwManager) LastError() string {
	u.mu.Lock()
	defer u.mu.Unlock()
	return u.lastErr
}

// allow opens port/proto in ufw and records it, bound to the given forward
// rule id (0 = shared/manual). The caller has checked available().
func (u *ufwManager) allow(port int, proto string, ruleID int64) {
	if u.db.HasUfwRule(port, proto) {
		return
	}
	spec := fmt.Sprintf("%d/%s", port, proto)
	out, err := ufwRun("allow", spec)
	if err != nil {
		log.Printf("ufw allow %s: %v: %s", spec, err, out)
		u.setErr(fmt.Sprintf("ufw allow %s: %v: %s", spec, err, out))
		return
	}
	u.setErr("")
	if strings.Contains(out, "Skipping") {
		// The rule was there before the panel asked for it, so it is not ours
		// to track (and later delete).
		return
	}
	_ = u.db.AddUfwRule(port, proto, ruleID)
	log.Printf("ufw: allowed %s", spec)
}

// revokeRule deletes one tracked ufw rule from ufw and the tracking table.
func (u *ufwManager) revokeRule(r UfwRule) {
	spec := fmt.Sprintf("%d/%s", r.Port, r.Proto)
	if out, err := ufwRun("delete", "allow", spec); err != nil {
		log.Printf("ufw delete allow %s: %v: %s", spec, err, out)
		u.setErr(fmt.Sprintf("ufw delete allow %s: %v: %s", spec, err, out))
	} else {
		u.setErr("")
		log.Printf("ufw: revoked %s", spec)
	}
	_ = u.db.DeleteUfwRule(r.ID)
}

// revoke removes a ufw rule by its tracking id (manual revoke from Settings).
func (u *ufwManager) revoke(id int64) {
	r, err := u.db.GetUfwRule(id)
	if err != nil || r == nil {
		return
	}
	u.revokeRule(*r)
}

// revokeForRule removes the ufw rules bound to a specific forward rule, and
// the shared tunnel port once no forward needs it any more.
func (u *ufwManager) revokeForRule(ruleID int64) {
	rules, err := u.db.ListUfwRulesByRule(ruleID)
	if err != nil {
		return
	}
	for _, r := range rules {
		u.revokeRule(r)
	}
	u.pruneShared()
}

// pruneShared revokes shared (rule_id 0) ufw rules that nothing uses: anything
// but the current tunnel port, and the tunnel port itself for a protocol that
// has no direct forward left.
func (u *ufwManager) pruneShared() {
	shared, err := u.db.ListUfwRulesByRule(0)
	if err != nil || len(shared) == 0 {
		return
	}
	forwards, err := u.db.ListForwardRules()
	if err != nil {
		return
	}
	used := map[string]bool{}
	for _, f := range forwards {
		used[f.Proto] = true
	}
	port := u.tunnelPort()
	for _, r := range shared {
		if r.Port != port || !used[r.Proto] {
			u.revokeRule(r)
		}
	}
}

// allowForward opens the host ports a forward rule needs: its host port (bound
// to the rule so it is revoked with it) plus the shared tunnel port for direct
// tcp/udp modes (bound to 0 — shared across rules).
func (u *ufwManager) allowForward(rule ForwardRule) {
	if !u.available() {
		return
	}
	u.allowForwardPorts(rule)
}

func (u *ufwManager) allowForwardPorts(rule ForwardRule) {
	// "http" (long-poll) and "tcp" forwards both listen on TCP on the host.
	hostProto, direct := "tcp", rule.Proto == "tcp"
	if rule.Proto == "udp" {
		hostProto, direct = "udp", true
	}
	// A listener bound to loopback is not reachable from outside anyway.
	if ip := net.ParseIP(rule.ListenAddr); ip == nil || !ip.IsLoopback() {
		u.allow(rule.HostPort, hostProto, rule.ID)
	}
	if port := u.tunnelPort(); direct && port > 0 {
		u.allow(port, hostProto, 0)
	}
}

// sync brings ufw in line with the saved forward rules: it opens what is
// missing (rules made while ufw or the integration was off, or a tunnel port
// that has since changed) and drops shared rules nothing uses.
func (u *ufwManager) sync() {
	if !u.available() {
		return
	}
	forwards, err := u.db.ListForwardRules()
	if err != nil {
		return
	}
	for _, f := range forwards {
		u.allowForwardPorts(f)
	}
	u.pruneShared()
}