// Command provision reconciles a Telegram presence with its declared
// specification.
//
// It is the provisioning plane, and it is deliberately separate from the
// adapter: the adapter holds a bot token with post_messages and nothing else,
// and has no code path into here. A compromised adapter cannot create, rename,
// delete or re-permission anything.
//
// See docs/provisioning.md for the design and docs/seeding-runbook.md for the
// steps that precede the first run.
package main

import (
	"flag"
	"fmt"
	"os"
	"path/filepath"

	"github.com/tegwick/fluid-telegram/internal/plan"
	"github.com/tegwick/fluid-telegram/internal/spec"
	"github.com/tegwick/fluid-telegram/internal/state"
)

const usage = `provision -- reconcile a Telegram presence with its declared spec

  provision plan  --spec <path> [--check]   show what would change; writes nothing
  provision apply --spec <path>             execute an approved plan

  session bootstrap / session check         mint and inspect the operator session

Flags:
  --spec   path to the presence spec (campaign repo)
  --root   repo root holding presence/resolved/ (default: cwd)
  --check  exit non-zero if anything would change; for scheduled drift checks
`

func main() {
	if len(os.Args) < 2 {
		fmt.Fprint(os.Stderr, usage)
		os.Exit(2)
	}
	var err error
	switch os.Args[1] {
	case "plan":
		err = cmdPlan(os.Args[2:])
	case "apply":
		err = fmt.Errorf("apply is not implemented yet (FT-WP-0002 T04); plan is safe to run")
	case "session":
		err = fmt.Errorf("session is not implemented yet (FT-WP-0002 T01)")
	case "-h", "--help", "help":
		fmt.Print(usage)
		return
	default:
		err = fmt.Errorf("unknown command %q", os.Args[1])
	}
	if err != nil {
		fmt.Fprintln(os.Stderr, "provision:", err)
		os.Exit(1)
	}
}

func cmdPlan(args []string) error {
	fs := flag.NewFlagSet("plan", flag.ExitOnError)
	specPath := fs.String("spec", "", "path to the presence spec")
	root := fs.String("root", ".", "repo root holding presence/resolved/")
	check := fs.Bool("check", false, "exit non-zero if anything would change")
	fs.Parse(args)

	if *specPath == "" {
		return fmt.Errorf("--spec is required")
	}

	sp, digest, err := spec.Load(*specPath)
	if err != nil {
		return err
	}
	statePath := state.Path(*root, sp.Campaign)
	rs, err := state.Load(statePath)
	if err != nil {
		return err
	}

	// Live observation needs the operator session, which does not exist yet.
	// Until it does, plan runs against the resolved state alone and says so --
	// an offline plan is still worth reading on a first run, where everything is
	// a creation, but it must not be mistaken for a drift check.
	live, offline := liveOrOffline()

	p, err := plan.Compute(sp, digest, rs, live)
	if err != nil {
		return err
	}

	fmt.Print(p.Render())
	if offline {
		fmt.Printf("\nnote: no operator session, so nothing was observed live.\n"+
			"      this plan reflects %s and the spec only.\n", relOrAbs(statePath))
		if *check {
			return fmt.Errorf("--check needs live observation; see docs/seeding-runbook.md")
		}
	}
	if *check && !p.Empty() {
		return fmt.Errorf("presence has drifted from the spec")
	}
	// A block means the world disagrees with the state file; a deferral is the
	// design working. Only the first is a failure.
	if p.Blocked() {
		os.Exit(1)
	}
	return nil
}

// offlineLive answers only what can be known without a session. It never claims
// something is fine; where it cannot tell, plan is told the presence is intact
// so that a first run still renders, and the caller reports that it was offline.
type offlineLive struct{}

func (offlineLive) BotExists(string) (bool, error) { return true, nil }
func (offlineLive) ChannelAdminRights(int64) ([]string, error) {
	return []string{spec.PostMessages}, nil
}
func (offlineLive) ChannelUsername(int64) (string, error) { return "", nil }

func liveOrOffline() (plan.Live, bool) {
	// FT-WP-0002 T03/T04: return the MTProto client once the session exists.
	return offlineLive{}, true
}

func relOrAbs(p string) string {
	if abs, err := filepath.Abs(p); err == nil {
		if wd, err := os.Getwd(); err == nil {
			if rel, err := filepath.Rel(wd, abs); err == nil {
				return rel
			}
		}
	}
	return p
}