package systemd

import (
	"fmt"
	"strings"
	"text/template"

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

const systemUnitTemplate = `# /etc/systemd/system/{{.ServiceName}}
# Generated by unitdore — do not edit manually

[Unit]
Description=Unitdore: {{.Unit.Name}} ({{.Unit.Runtime}})
After=network.target{{with .RuntimeService}} {{.}}
Requires={{.}}{{end}}

[Service]
Type=simple
ExecStart={{.ExecStart}}
ExecStop={{.ExecStop}}
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
`

const userUnitTemplate = `# ~/.config/systemd/user/{{.ServiceName}}
# Generated by unitdore — do not edit manually

[Unit]
Description=Unitdore: {{.Unit.Name}} ({{.Unit.Runtime}})
After=default.target

[Service]
Type=simple
ExecStart={{.ExecStart}}
ExecStop={{.ExecStop}}
Restart=on-failure
RestartSec=5

[Install]
WantedBy=default.target
`

type templateData struct {
	ServiceName    string
	Unit           config.Unit
	ExecStart      string
	ExecStop       string
	RuntimeService string
}

// ServiceName returns the systemd service name for a unit, with optional prefix/suffix.
func ServiceName(u config.Unit, prefix, suffix string) string {
	return fmt.Sprintf("unitdore-%s%s%s.service", prefix, u.Name, suffix)
}

// Generate produces the .service file content for a unit.
func Generate(u config.Unit, prefix, suffix string) (string, error) {
	execStart, execStop := buildExecCommands(u)

	data := templateData{
		ServiceName:    ServiceName(u, prefix, suffix),
		Unit:           u,
		ExecStart:      execStart,
		ExecStop:       execStop,
		RuntimeService: runtimeService(u.Runtime),
	}

	tmplStr := systemUnitTemplate
	if u.User != "" {
		tmplStr = userUnitTemplate
	}

	tmpl, err := template.New("unit").Parse(tmplStr)
	if err != nil {
		return "", fmt.Errorf("parsing template: %w", err)
	}

	var buf strings.Builder
	if err := tmpl.Execute(&buf, data); err != nil {
		return "", fmt.Errorf("rendering template: %w", err)
	}
	return buf.String(), nil
}

// runtimeService returns the systemd service name that must be running for the
// given container runtime, or "" if none is required (e.g. daemonless podman).
func runtimeService(runtime string) string {
	if runtime == "docker" {
		return "docker.service"
	}
	return ""
}

func buildExecCommands(u config.Unit) (start, stop string) {
	// If a custom command is provided, use it directly
	if u.Command != "" {
		return u.Command, ""
	}

	switch u.Runtime {
	case "podman":
		start = fmt.Sprintf("/usr/bin/podman start -a %s", u.Name)
		stop = fmt.Sprintf("/usr/bin/podman stop %s", u.Name)
	case "docker":
		start = fmt.Sprintf("/usr/bin/docker start %s", u.Name)
		stop = fmt.Sprintf("/usr/bin/docker stop %s", u.Name)
	default:
		start = fmt.Sprintf("/usr/bin/%s start %s", u.Runtime, u.Name)
		stop = fmt.Sprintf("/usr/bin/%s stop %s", u.Runtime, u.Name)
	}
	return start, stop
}