package emitter

import (
	"errors"
	"fmt"
	"strings"

	"git.cloudinit.dev/coreci/orca/internal/jobspec"
)

// SystemdEmitter is a stub Emitter implementation for the "process"
// runtime. It renders a minimal systemd unit file for the workload.
//
// This is a STUB — the full systemd emitter (with lifecycle hooks,
// sockets, EnvironmentFile, LoadCredential) lands in later phases:
//
//   - P04: lifecycle hooks (ExecStop, ExecStartPre/Post, timeouts)
//   - P08: socket plumbing (R-007)
//   - v0.10-P03: secrets via EnvironmentFile= + LoadCredential=
//
// P0c ships only the minimal [Service]\nExecStart=... shape to prove
// the Emitter interface end-to-end. The unit name carries the
// `orca-v1-` prefix per the dual-write window (REQ-090) so the v0.9
// SSH-push path does not collide with the v0.8 daemon's
// `orca-<job>.service` units during the migration window.
type SystemdEmitter struct{}

// unitNamePrefix is the v0.9 SSH-push unit-name prefix. The v0.8
// daemon uses `orca-<job>.service`; the v0.9 path uses
// `orca-v1-<spec.Name>.service` so the two never overlap (REQ-090,
// I-C-006). The prefix is load-bearing — do not change it without
// updating the dual-write window contract.
const unitNamePrefix = "orca-v1-"

// Render renders a minimal systemd unit file for a process-runtime
// workload. The unit name is `/etc/systemd/system/<unitNamePrefix><spec.Name>.service`
// and the content is a minimal `[Service]` block with the runtime
// command as ExecStart. Mode is 0644 (the lead applier chmods after
// atomic rename).
//
// Returns an error if the spec is nil, the spec is missing its name,
// or the runtime command is empty (a workload with no command has
// nothing to ExecStart).
func (SystemdEmitter) Render(spec *jobspec.WorkloadSpec, node *Node) ([]File, error) {
	if spec == nil {
		return nil, errors.New("emitter/systemd: spec is nil")
	}
	if strings.TrimSpace(spec.Name) == "" {
		return nil, errors.New("emitter/systemd: spec name is empty")
	}
	if spec.Runtime == nil {
		return nil, errors.New("emitter/systemd: runtime block is nil")
	}
	if strings.TrimSpace(spec.Runtime.Command) == "" {
		return nil, errors.New("emitter/systemd: runtime command is empty")
	}
	path := fmt.Sprintf("/etc/systemd/system/%s%s.service", unitNamePrefix, spec.Name)
	content := fmt.Sprintf("[Service]\nExecStart=%s\n", spec.Runtime.Command)
	return []File{{Path: path, Content: content, Mode: "0644"}}, nil
}