package app

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"gitea.maximumdirect.net/eric/narratio/internal/adapters/storage"
	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
	"gitea.maximumdirect.net/eric/narratio/internal/audio"
	"gitea.maximumdirect.net/eric/narratio/internal/config"
	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
)

// RestoreExecutionResult captures concrete file-install results for one restore execution.
type RestoreExecutionResult struct {
	DownloadedCount int
}

func executeRestorePlan(
	ctx context.Context,
	cfg *config.Config,
	current *RemoteCurrentState,
	plan *RestorePlan,
	report *RestoreReport,
	store storage.ObjectStore,
) (*RestoreExecutionResult, error) {
	if cfg == nil || cfg.Pipeline == nil || cfg.Session == nil {
		return nil, fmt.Errorf("resolved config with pipeline/session is required")
	}
	if current == nil {
		return nil, fmt.Errorf("remote current state is required")
	}
	if plan == nil {
		return nil, fmt.Errorf("restore plan is required")
	}
	if store == nil {
		return nil, fmt.Errorf("remote object store is required")
	}

	sessionRoot := artifacts.SessionWorkDirForCampaign(cfg.Pipeline.Workspace.Root, cfg.Session.Campaign, cfg.Session.SessionID)
	manifestActions := make([]RestoreAction, 0, 1)
	actions := make([]RestoreAction, 0, len(plan.Actions))
	for _, action := range plan.Actions {
		if action.Kind != RestoreActionDownload {
			continue
		}
		if action.LocalRelativePath == config.PathManifestFile {
			manifestActions = append(manifestActions, action)
			continue
		}
		actions = append(actions, action)
	}
	if len(manifestActions) > 1 {
		return nil, fmt.Errorf("restore plan includes multiple manifest download actions")
	}
	if len(manifestActions) == 1 {
		actions = append(actions, manifestActions[0])
	}

	result := &RestoreExecutionResult{}
	for _, action := range actions {
		if err := executeRestoreDownloadAction(ctx, cfg, sessionRoot, current, action, store); err != nil {
			if report != nil {
				report.markFailed(action, err)
			}
			return nil, fmt.Errorf("install %q from %q: %w", action.LocalRelativePath, action.RemoteKey, err)
		}
		if report != nil {
			report.markDownloaded(action)
		}
		result.DownloadedCount++
	}

	return result, nil
}

func executeRestoreDownloadAction(
	ctx context.Context,
	cfg *config.Config,
	sessionRoot string,
	current *RemoteCurrentState,
	action RestoreAction,
	store storage.ObjectStore,
) error {
	safeLocalPath, err := joinWithinSessionRoot(sessionRoot, action.LocalRelativePath)
	if err != nil {
		return fmt.Errorf("resolve safe local path: %w", err)
	}
	if strings.TrimSpace(action.LocalPath) != "" && filepath.Clean(action.LocalPath) != safeLocalPath {
		return fmt.Errorf("restore plan local path mismatch for %q", action.LocalRelativePath)
	}

	if restoreActionIsAudio(action) {
		return executeRestoreAudioAction(ctx, cfg, safeLocalPath, action, store)
	}

	tmpPath, err := downloadObjectToSiblingTemp(ctx, store, action.RemoteKey, safeLocalPath)
	if err != nil {
		return fmt.Errorf("download to temp file: %w", err)
	}
	removeTmp := true
	defer func() {
		if removeTmp {
			_ = os.Remove(tmpPath)
		}
	}()

	if action.LocalRelativePath == config.PathManifestFile {
		if err := validateRestoredManifest(ctx, cfg, current, tmpPath); err != nil {
			return err
		}
	}

	if err := fileops.InstallDownloadedTempFile(tmpPath, safeLocalPath, 0o644); err != nil {
		return fmt.Errorf("install file atomically: %w", err)
	}
	removeTmp = false

	return nil
}

func executeRestoreAudioAction(
	ctx context.Context,
	cfg *config.Config,
	safeLocalPath string,
	action RestoreAction,
	store storage.ObjectStore,
) error {
	if cfg == nil || cfg.Pipeline == nil || cfg.Pipeline.Storage.S3 == nil || cfg.Session == nil {
		return fmt.Errorf("resolved s3 config and session are required")
	}
	spoolDir := artifacts.SessionSpoolRestoreAudioDir(cfg.Pipeline.Spool.Root, cfg.Session.Campaign, cfg.Session.SessionID)
	spoolPath := filepath.Join(spoolDir, filepath.Base(safeLocalPath))
	cacheEnabled := cfg.Pipeline.Cache.S3Audio == nil || *cfg.Pipeline.Cache.S3Audio
	_, err := audio.MaterializeS3Audio(ctx, audio.S3MaterializeRequest{
		Store: store,
		Object: storage.ObjectInfo{
			Key:  action.RemoteKey,
			Size: action.Size,
			ETag: action.ETag,
		},
		Bucket:       strings.TrimSpace(cfg.Pipeline.Storage.S3.Bucket),
		CacheRoot:    strings.TrimSpace(cfg.Pipeline.Cache.Root),
		CacheEnabled: cacheEnabled,
		SpoolPath:    spoolPath,
		DestPath:     safeLocalPath,
	})
	if err != nil {
		return fmt.Errorf("materialize audio: %w", err)
	}
	return nil
}

func downloadObjectToSiblingTemp(ctx context.Context, store storage.ObjectStore, remoteKey, destPath string) (string, error) {
	if strings.TrimSpace(destPath) == "" {
		return "", fmt.Errorf("destination path is required")
	}
	dir := filepath.Dir(destPath)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", fmt.Errorf("create destination directory: %w", err)
	}
	base := filepath.Base(destPath)
	tmp, err := os.CreateTemp(dir, "."+base+".restore-*.tmp")
	if err != nil {
		return "", fmt.Errorf("create temp file: %w", err)
	}
	tmpPath := tmp.Name()
	if err := tmp.Close(); err != nil {
		_ = os.Remove(tmpPath)
		return "", fmt.Errorf("close temp file: %w", err)
	}

	if err := store.Download(ctx, remoteKey, tmpPath); err != nil {
		_ = os.Remove(tmpPath)
		return "", err
	}

	return tmpPath, nil
}

func validateRestoredManifest(ctx context.Context, cfg *config.Config, current *RemoteCurrentState, path string) error {
	manifestStore := &manifest.LocalStore{}
	m, err := manifestStore.Load(ctx, path)
	if err != nil {
		return fmt.Errorf("validate manifest decode: %w", err)
	}

	requestedSession := strings.TrimSpace(cfg.Session.SessionID)
	requestedCampaign := strings.TrimSpace(cfg.Session.Campaign)
	manifestSession := strings.TrimSpace(m.SessionID)
	manifestCampaign := strings.TrimSpace(m.Campaign)
	if manifestSession != requestedSession {
		return fmt.Errorf("manifest session_id %q does not match requested session_id %q", manifestSession, requestedSession)
	}
	if manifestCampaign == "" {
		return fmt.Errorf("manifest campaign is required")
	}
	if manifestCampaign != requestedCampaign {
		return fmt.Errorf("manifest campaign %q does not match requested campaign %q", manifestCampaign, requestedCampaign)
	}
	if current != nil {
		if expected := strings.TrimSpace(current.SessionID); expected != "" && manifestSession != expected {
			return fmt.Errorf("manifest session_id %q does not match discovered session_id %q", manifestSession, expected)
		}
		if expected := strings.TrimSpace(current.Campaign); expected != "" && manifestCampaign != expected {
			return fmt.Errorf("manifest campaign %q does not match discovered campaign %q", manifestCampaign, expected)
		}
	}

	return nil
}