// Package openrc generates and manages OpenRC init scripts.
//
// Services run at system level (root only). Units with a user run as that
// user through command_user, with HOME and XDG_RUNTIME_DIR set.
package openrc

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

	"github.com/warkanum/unitdore/config"
	"github.com/warkanum/unitdore/service"
)

const runlevel = "default"

// Overridable for tests.
var (
	initDir = "/etc/init.d"

	// runCmd runs a command with stdio passed through.
	runCmd = func(name string, args ...string) error {
		cmd := exec.Command(name, args...)
		cmd.Stdout = os.Stdout
		cmd.Stderr = os.Stderr
		return cmd.Run()
	}
	// outCmd runs a command and returns its combined output.
	outCmd = func(name string, args ...string) ([]byte, error) {
		return exec.Command(name, args...).CombinedOutput()
	}
)

// Backend is the OpenRC implementation of the init interface.
type Backend struct{}

func (Backend) Name() string { return "openrc" }

// SupportsLinger is false: OpenRC services need no linger.
func (Backend) SupportsLinger() bool { return false }

func (Backend) ServiceName(u config.Unit, prefix, suffix string) string {
	return service.BaseName(u, prefix, suffix)
}

func (b Backend) UnitPath(u config.Unit, prefix, suffix string) (string, error) {
	return filepath.Join(initDir, b.ServiceName(u, prefix, suffix)), nil
}

func (b Backend) IsInstalled(u config.Unit, prefix, suffix string) bool {
	path, _ := b.UnitPath(u, prefix, suffix)
	_, err := os.Stat(path)
	return err == nil
}

func (b Backend) Install(u config.Unit, prefix, suffix string) error {
	if err := service.RequireRoot("openrc"); err != nil {
		return err
	}
	content, err := b.Generate(u, prefix, suffix)
	if err != nil {
		return err
	}
	path, _ := b.UnitPath(u, prefix, suffix)
	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
		return fmt.Errorf("creating init dir: %w", err)
	}
	if err := os.WriteFile(path, []byte(content), 0755); err != nil {
		return fmt.Errorf("writing init script: %w", err)
	}
	return nil
}

func (b Backend) Uninstall(u config.Unit, prefix, suffix string) error {
	if err := service.RequireRoot("openrc"); err != nil {
		return err
	}
	name := b.ServiceName(u, prefix, suffix)
	_ = runCmd("rc-update", "del", name, runlevel) // not in runlevel is fine
	path, _ := b.UnitPath(u, prefix, suffix)
	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("removing init script: %w", err)
	}
	return nil
}

// Enable adds the service to the default runlevel and starts it.
func (b Backend) Enable(u config.Unit, prefix, suffix string) error {
	if err := service.RequireRoot("openrc"); err != nil {
		return err
	}
	name := b.ServiceName(u, prefix, suffix)
	if err := runCmd("rc-update", "add", name, runlevel); err != nil {
		return err
	}
	return runCmd("rc-service", name, "start")
}

// Disable stops the service and removes it from the default runlevel.
func (b Backend) Disable(u config.Unit, prefix, suffix string) error {
	if err := service.RequireRoot("openrc"); err != nil {
		return err
	}
	name := b.ServiceName(u, prefix, suffix)
	if err := runCmd("rc-service", name, "stop"); err != nil {
		return err
	}
	_ = runCmd("rc-update", "del", name, runlevel) // not in runlevel is fine
	return nil
}

func (b Backend) Start(u config.Unit, prefix, suffix string) error {
	if err := service.RequireRoot("openrc"); err != nil {
		return err
	}
	return runCmd("rc-service", b.ServiceName(u, prefix, suffix), "start")
}

func (b Backend) Stop(u config.Unit, prefix, suffix string) error {
	if err := service.RequireRoot("openrc"); err != nil {
		return err
	}
	return runCmd("rc-service", b.ServiceName(u, prefix, suffix), "stop")
}

func (b Backend) Status(u config.Unit, prefix, suffix string) string {
	// rc-service status exits non-zero for stopped services but still prints
	out, _ := outCmd("rc-service", b.ServiceName(u, prefix, suffix), "status")
	return parseStatus(string(out))
}

// parseStatus maps `rc-service <name> status` output to a systemd-like state.
func parseStatus(out string) string {
	out = strings.ToLower(out)
	switch {
	case strings.Contains(out, "crashed"):
		return "failed"
	case strings.Contains(out, "starting"):
		return "activating"
	case strings.Contains(out, "stopping"):
		return "deactivating"
	case strings.Contains(out, "started"):
		return "active"
	case strings.Contains(out, "stopped"):
		return "inactive"
	default:
		return "unknown"
	}
}

// Generate produces the init script for a unit.
func (b Backend) Generate(u config.Unit, prefix, suffix string) (string, error) {
	if err := service.Validate(u); err != nil {
		return "", err
	}
	user, err := service.LookupUser(u.User)
	if err != nil {
		return "", err
	}
	spec := service.Resolve(u)

	var w strings.Builder
	w.WriteString("#!/sbin/openrc-run\n")
	w.WriteString("# " + filepath.Join(initDir, b.ServiceName(u, prefix, suffix)) + "\n")
	w.WriteString("# Generated by unitdore — do not edit manually\n\n")
	fmt.Fprintf(&w, "description=%s\n", dq(fmt.Sprintf("Unitdore: %s (%s)", u.Name, spec.Label)))

	if user != nil {
		fmt.Fprintf(&w, "export HOME=%s\n", service.ShellQuote(user.Home))
		fmt.Fprintf(&w, "export XDG_RUNTIME_DIR=%s\n", service.ShellQuote(user.RuntimeDir))
	}

	start, err := service.ShellCommand(spec.Start)
	if err != nil {
		return "", fmt.Errorf("unit %s: %w", u.Name, err)
	}
	stop := ""
	if spec.Stop != "" {
		if stop, err = service.ShellCommand(spec.Stop); err != nil {
			return "", fmt.Errorf("unit %s: %w", u.Name, err)
		}
	}

	if spec.Type == service.TypeOneshot {
		writeOneshot(&w, spec, user, start, stop)
	} else if err := writeSupervised(&w, u, spec, user); err != nil {
		return "", err
	}

	w.WriteString("\ndepend() {\n\tneed net\n")
	if u.Runtime == "docker" {
		w.WriteString("\tneed docker\n")
	}
	if len(u.After) > 0 {
		names := make([]string, len(u.After))
		for i, n := range u.After {
			names[i] = service.BaseName(config.Unit{Name: n}, prefix, suffix)
		}
		fmt.Fprintf(&w, "\tafter %s\n", strings.Join(names, " "))
	}
	w.WriteString("}\n")

	var pre []string
	if spec.Type != service.TypeOneshot && user != nil {
		pre = append(pre, fmt.Sprintf("checkpath -d -m 0700 -o %s %s",
			service.ShellQuote(user.Name), service.ShellQuote(user.RuntimeDir)))
	}
	if secs := delaySeconds(u); secs > 0 {
		pre = append(pre, fmt.Sprintf("sleep %d", secs))
	}
	if len(pre) > 0 {
		fmt.Fprintf(&w, "\nstart_pre() {\n\t%s\n}\n", strings.Join(pre, "\n\t"))
	}

	if spec.Type != service.TypeOneshot {
		if stop != "" {
			fmt.Fprintf(&w, "\nstop_pre() {\n\t%s || true\n}\n", asUser(user, stop))
		}
	}
	return w.String(), nil
}

// writeSupervised writes the variables for a long-running foreground command.
func writeSupervised(w *strings.Builder, u config.Unit, spec service.Spec, user *service.UserEnv) error {
	argv, err := service.SplitCommand(spec.Start)
	if err != nil {
		return fmt.Errorf("unit %s: %w", u.Name, err)
	}
	if len(argv) == 0 {
		return fmt.Errorf("unit %s: empty command", u.Name)
	}

	w.WriteString("\n")
	if u.Restart {
		w.WriteString("supervisor=supervise-daemon\n")
		fmt.Fprintf(w, "respawn_delay=%d\n", u.RestartSec)
		if u.RestartRetries > 0 {
			fmt.Fprintf(w, "respawn_max=%d\n", u.RestartRetries)
		}
	} else {
		w.WriteString("command_background=yes\n")
		w.WriteString("pidfile=\"/run/${RC_SVCNAME}.pid\"\n")
	}

	fmt.Fprintf(w, "command=%s\n", dq(argv[0]))
	if len(argv) > 1 {
		quoted := make([]string, len(argv)-1)
		for i, a := range argv[1:] {
			quoted[i] = service.ShellQuote(a)
		}
		fmt.Fprintf(w, "command_args=%s\n", dq(strings.Join(quoted, " ")))
	}
	if spec.WorkingDir != "" {
		fmt.Fprintf(w, "directory=%s\n", dq(spec.WorkingDir))
	}
	if user != nil {
		fmt.Fprintf(w, "command_user=%s\n", dq(user.Name))
	}
	return nil
}

// writeOneshot writes start/stop functions; OpenRC tracks the started state.
func writeOneshot(w *strings.Builder, spec service.Spec, user *service.UserEnv, start, stop string) {
	w.WriteString("\nstart() {\n\tebegin \"Starting $RC_SVCNAME\"\n")
	if spec.WorkingDir != "" {
		fmt.Fprintf(w, "\tcd %s || return 1\n", service.ShellQuote(spec.WorkingDir))
	}
	fmt.Fprintf(w, "\t%s\n\teend $?\n}\n", asUser(user, start))
	if stop != "" {
		w.WriteString("\nstop() {\n\tebegin \"Stopping $RC_SVCNAME\"\n")
		if spec.WorkingDir != "" {
			fmt.Fprintf(w, "\tcd %s || return 1\n", service.ShellQuote(spec.WorkingDir))
		}
		fmt.Fprintf(w, "\t%s\n\teend $?\n}\n", asUser(user, stop))
	}
}

// asUser wraps a shell command line so it runs as the unit's user, keeping the
// exported HOME / XDG_RUNTIME_DIR.
func asUser(user *service.UserEnv, cmd string) string {
	if user == nil {
		return cmd
	}
	return fmt.Sprintf("su -m -s /bin/sh -c %s %s", service.ShellQuote(cmd), service.ShellQuote(user.Name))
}

// dq double-quotes s for an OpenRC (sh) variable assignment.
func dq(s string) string {
	r := strings.NewReplacer(`\`, `\\`, `"`, `\"`, "$", `\$`, "`", "\\`")
	return `"` + r.Replace(s) + `"`
}

// delaySeconds rounds the unit's start delay up to whole seconds.
func delaySeconds(u config.Unit) int {
	return int((u.StartDelay + time.Second - 1) / time.Second)
}