package app

import (
	"context"
	"flag"
	"fmt"
	"io"

	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
	"gitea.maximumdirect.net/eric/narratio/internal/config"
)

// Plan validates configuration, prepares the local workdir, and prints stage order.
func Plan(_ context.Context, args []string, out io.Writer) error {
	fs := flag.NewFlagSet("plan", flag.ContinueOnError)
	fs.SetOutput(io.Discard)

	var pipelinePath string
	var sessionPath string
	var force bool
	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml")
	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
	fs.BoolVar(&force, "force", false, "force stage execution (reserved for future behavior)")

	if err := fs.Parse(args); err != nil {
		return fmt.Errorf("plan: invalid flags: %w", err)
	}
	if fs.NArg() != 0 {
		return fmt.Errorf("plan: unexpected positional arguments")
	}
	if pipelinePath == "" || sessionPath == "" {
		return fmt.Errorf("plan: --config and --session are required")
	}

	cfg, err := config.Load(pipelinePath, sessionPath)
	if err != nil {
		return fmt.Errorf("plan: %w", err)
	}
	if err := config.Validate(cfg); err != nil {
		return fmt.Errorf("plan: %w", err)
	}

	store := artifacts.NewLocalStore(cfg.Pipeline.Workspace.Root)
	paths, err := store.EnsureLayout(cfg.Session.SessionID)
	if err != nil {
		return fmt.Errorf("plan: prepare workdir: %w", err)
	}

	_ = force // TODO: use --force in future skip/stale planning behavior.

	stages := BuildFullPlan()
	if _, err := fmt.Fprintf(out, "narratio plan: workdir prepared at %s\n", paths.Root); err != nil {
		return err
	}
	for _, s := range stages {
		if _, err := fmt.Fprintln(out, s.Name()); err != nil {
			return err
		}
	}

	return nil
}