package manifest

import (
	"encoding/json"
	"os"
	"sync"
)

// Entry is one copied file record
type Entry struct {
	Source    string `json:"source"`
	LocalDest string `json:"localDest"`
	S3Path    string `json:"s3Path,omitempty"`
	SHA256    string `json:"sha256"`
	Bytes     int64  `json:"bytes"`
	Status    string `json:"status"` // "local" | "s3" | "done" | "error"
	Error     string `json:"error,omitempty"`
}

// Manifest holds all entries for a session
type Manifest struct {
	SessionID string  `json:"sessionID"`
	Entries   []Entry `json:"entries"`
	mu        sync.Mutex
}

// New creates a new manifest
func New(sessionID string) *Manifest {
	return &Manifest{SessionID: sessionID}
}

// Append adds an entry atomically
func (m *Manifest) Append(e Entry) {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.Entries = append(m.Entries, e)
}

// Save writes manifest atomically via temp file + rename
func (m *Manifest) Save(path string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	data, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		return err
	}

	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, data, 0644); err != nil {
		return err
	}
	return os.Rename(tmp, path)
}

// Load reads a manifest from disk
func Load(path string) (*Manifest, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	var m Manifest
	if err := json.Unmarshal(data, &m); err != nil {
		return nil, err
	}
	return &m, nil
}