package session

import (
	"os"
	"path/filepath"
	"sort"
	"strings"
)

// Info describes one session file in a directory.
type Info struct {
	ID      string
	Path    string
	Name    string
	CWD     string
	Leaf    string
	Updated string
}

// List returns session files in dir, newest first.
func List(dir string) ([]Info, error) {
	ents, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}
	var out []Info
	for _, ent := range ents {
		name := ent.Name()
		if ent.IsDir() || !strings.HasSuffix(name, ".jsonl") {
			continue
		}
		path := filepath.Join(dir, name)
		st, err := Open(path)
		if err != nil {
			continue
		}
		info, err := st.Info()
		if err != nil {
			continue
		}
		out = append(out, info)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Updated > out[j].Updated })
	return out, nil
}

// Continue opens the newest session whose cwd matches. A second return
// value of false means there is nothing to continue.
func Continue(dir, cwd string) (*Store, bool, error) {
	list, err := List(dir)
	if err != nil {
		return nil, false, err
	}
	for _, info := range list {
		if cwd == "" || info.CWD == cwd {
			st, err := Open(info.Path)
			return st, err == nil, err
		}
	}
	return nil, false, nil
}

// Resume opens a session by id (filename stem) or by name.
func Resume(dir, idOrName string) (*Store, error) {
	list, err := List(dir)
	if err != nil {
		return nil, err
	}
	for _, info := range list {
		if info.ID == idOrName || info.Name == idOrName {
			return Open(info.Path)
		}
	}
	return nil, os.ErrNotExist
}

// SetCWD records the working directory used by Continue.
func (s *Store) SetCWD(cwd string) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.writeMetaKeyLocked("cwd", cwd)
}

// Info reads the catalog fields for this file.
func (s *Store) Info() (Info, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	entries, err := s.readEntriesLocked()
	if err != nil {
		return Info{}, err
	}
	meta := s.readMetaLocked()
	updated := ""
	if len(entries) > 0 {
		updated = entries[len(entries)-1].Timestamp
	}
	id := strings.TrimSuffix(filepath.Base(s.path), ".jsonl")
	return Info{
		ID: id, Path: s.path, Name: meta["name"], CWD: meta["cwd"],
		Leaf: s.leafLocked(entries), Updated: updated,
	}, nil
}