package app

import (
	"context"
	"flag"
	"fmt"
	"io"
	"log/slog"
	"os"

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

// Plan validates configuration, prepares the local workdir, and prints stage order.
func Plan(ctx 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 sessionID string
	var force bool
	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml (optional; defaults searched)")
	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
	fs.StringVar(&sessionID, "session-id", "", "session identifier for session.yml templates")
	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")
	}
	resolvedPipelinePath, err := resolvePipelineConfigPath(pipelinePath)
	if err != nil {
		return fmt.Errorf("plan: %w", err)
	}
	resolvedSessionPath, err := resolveSessionConfigPath(sessionPath)
	if err != nil {
		return fmt.Errorf("plan: %w", err)
	}

	cfg, err := config.LoadWithSessionOptions(resolvedPipelinePath, resolvedSessionPath, config.SessionLoadOptions{
		SessionID: sessionID,
	})
	if err != nil {
		return fmt.Errorf("plan: %w", err)
	}
	if err := config.Validate(cfg); err != nil {
		return fmt.Errorf("plan: %w", err)
	}
	if _, err := loadSecretsFromConfig(cfg, logging.NewLogger(os.Stderr, slog.LevelInfo)); err != nil {
		return fmt.Errorf("plan: %w", err)
	}

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

	stages := BuildFullPlan()
	var m *manifest.Manifest
	m, err = loadManifestIfPresent(ctx, cfg)
	if err != nil {
		return fmt.Errorf("plan: %w", err)
	}
	decisions := decideStageActions(stages, m, force)

	runCount := 0
	skipCount := 0
	if _, err := fmt.Fprintf(out, "narratio plan: workdir prepared at %s\n", paths.Root); err != nil {
		return err
	}
	for _, d := range decisions {
		if d.Action == stageActionRun {
			runCount++
		} else {
			skipCount++
		}
		if _, err := fmt.Fprintf(out, "%s: %s\n", d.Stage.Name(), d.Action); err != nil {
			return err
		}
	}
	if _, err := fmt.Fprintf(out, "totals: run=%d skip=%d\n", runCount, skipCount); err != nil {
		return err
	}

	return nil
}