package app

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"

	"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"
	"gitea.maximumdirect.net/eric/narratio/internal/stage"
)

type RunOptions struct {
	Force bool
}

type RunSummary struct {
	SessionID    string
	ManifestPath string
	StageNames   []string
}

func executeStages(ctx context.Context, cfg *config.Config, stages []stage.Stage, opts RunOptions) (*RunSummary, error) {
	store := artifacts.NewLocalStore(cfg.Pipeline.Workspace.Root)
	paths, err := store.EnsureLayout(cfg.Session.SessionID)
	if err != nil {
		return nil, fmt.Errorf("prepare workdir: %w", err)
	}

	lock, err := store.AcquireSessionLock(cfg.Session.SessionID)
	if err != nil {
		return nil, fmt.Errorf("acquire session lock: %w", err)
	}
	defer func() {
		_ = store.ReleaseSessionLock(lock)
	}()

	manifestStore := &manifest.LocalStore{}
	manifestPath := paths.ManifestPath

	m, err := loadOrCreateManifest(ctx, manifestStore, manifestPath, cfg.Session.SessionID)
	if err != nil {
		return nil, err
	}

	env := &Env{
		Config:        cfg,
		ArtifactStore: store,
		Logger:        logging.NewLogger(os.Stderr, slog.LevelInfo),
	}
	stageEnv := toStageEnv(env)

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

	runNames := make([]string, 0, len(stages))
	for _, s := range stages {
		runNames = append(runNames, s.Name())

		now := nowUTC()
		m.MarkStageRunning(s.Name(), now)
		if err := manifestStore.Save(ctx, manifestPath, m); err != nil {
			return nil, fmt.Errorf("save manifest before stage %q: %w", s.Name(), err)
		}

		result, err := s.Run(ctx, stageEnv, m)
		if err != nil {
			m.MarkStageFailed(s.Name(), nowUTC(), err.Error())
			if saveErr := manifestStore.Save(ctx, manifestPath, m); saveErr != nil {
				return nil, fmt.Errorf("stage %q failed (%v) and manifest save failed (%v)", s.Name(), err, saveErr)
			}
			return nil, fmt.Errorf("stage %q failed: %w", s.Name(), err)
		}

		outputs := mapResultOutputs(result)
		m.MarkStageSucceeded(s.Name(), nowUTC(), outputs)
		applyStageResultToManifest(m, s.Name(), result)

		if err := manifestStore.Save(ctx, manifestPath, m); err != nil {
			return nil, fmt.Errorf("save manifest after stage %q: %w", s.Name(), err)
		}
	}

	return &RunSummary{
		SessionID:    cfg.Session.SessionID,
		ManifestPath: manifestPath,
		StageNames:   runNames,
	}, nil
}

func loadOrCreateManifest(ctx context.Context, store *manifest.LocalStore, path, sessionID string) (*manifest.Manifest, error) {
	exists, err := fileExists(path)
	if err != nil {
		return nil, fmt.Errorf("check manifest existence %q: %w", path, err)
	}
	if exists {
		m, err := store.Load(ctx, path)
		if err != nil {
			return nil, fmt.Errorf("load manifest %q: %w", path, err)
		}
		return m, nil
	}

	m, err := store.Create(ctx, sessionID)
	if err != nil {
		return nil, fmt.Errorf("create manifest: %w", err)
	}
	if err := store.Save(ctx, path, m); err != nil {
		return nil, fmt.Errorf("save new manifest %q: %w", path, err)
	}
	return m, nil
}

func fileExists(path string) (bool, error) {
	_, err := os.Stat(path)
	if err == nil {
		return true, nil
	}
	if os.IsNotExist(err) {
		return false, nil
	}
	return false, err
}

func mapResultOutputs(result *stage.StageResult) []manifest.ArtifactRecord {
	if result == nil || len(result.Outputs) == 0 {
		return nil
	}

	out := make([]manifest.ArtifactRecord, 0, len(result.Outputs))
	for _, ref := range result.Outputs {
		localPath := ref.AbsolutePath
		if localPath == "" {
			localPath = ref.RelativePath
		}
		out = append(out, manifest.ArtifactRecord{
			Kind:      ref.Kind,
			LocalPath: localPath,
			RemoteKey: ref.RemoteKey,
			Checksum:  ref.Checksum,
		})
	}

	return out
}

func applyStageResultToManifest(m *manifest.Manifest, stageName string, result *stage.StageResult) {
	if m == nil || result == nil {
		return
	}
	sr := m.Stages[stageName]
	if sr == nil {
		return
	}
	if len(result.Logs) > 0 {
		sr.Logs = append([]string(nil), result.Logs...)
	}
	if len(result.GeneratedConfigs) > 0 {
		sr.GeneratedConfigs = append([]string(nil), result.GeneratedConfigs...)
	}
	if len(result.Metadata) > 0 {
		sr.Metadata = result.Metadata
	}
}

func manifestPathFor(cfg *config.Config) string {
	return filepath.Join(cfg.Pipeline.Workspace.Root, "work", cfg.Session.SessionID, "manifest.json")
}