// Package store defines storage interfaces and a filesystem-backed
// implementation used by the 9P server.
package store

import (
	"context"
	"os"
	"time"
)

// StoreEntry is an open handle to a single named blob.
type StoreEntry interface {
	Stat() (os.FileInfo, error)
	Read() ([]byte, error)
	Write(data []byte) error
	BlockingRead(ctx context.Context, base string) (content []byte, nextBase string, err error)
	// OneShot returns true if the entry yields data once per open (offset>0 → EOF).
	OneShot() bool
	// IsBlocking returns true if Read blocks until data is available (use BlockingRead).
	IsBlocking() bool
	// Async returns true if writes should be dispatched asynchronously.
	Async() bool
}

// Store is a named collection of entries.
type Store interface {
	Stat(name string) (os.FileInfo, error)
	List() ([]os.DirEntry, error)
	Open(name string) (StoreEntry, error)
	Create(name string) error
	Delete(name string) error
	Rename(oldName, newName string) error
}

// Runnable is a running agent that can be observed and controlled.
type Runnable interface {
	RunnableID() string
	Cancel()
	Interrupt()
	AppendLog([]byte)
	LogInfo() (length int, vers uint32)
}

// EntryConfig implements StoreEntry via function pointers.
type EntryConfig struct {
	StatFn         func() (os.FileInfo, error)
	ReadFn         func() ([]byte, error)
	WriteFn        func([]byte) error
	BlockingReadFn func(context.Context, string) ([]byte, string, error)
	OneShot_       bool
	IsBlocking_    bool
	Async_         bool
}

func (e *EntryConfig) Stat() (os.FileInfo, error)                              { return e.StatFn() }
func (e *EntryConfig) Read() ([]byte, error)                                   { return e.ReadFn() }
func (e *EntryConfig) Write(data []byte) error                                 { return e.WriteFn(data) }
func (e *EntryConfig) BlockingRead(ctx context.Context, base string) ([]byte, string, error) {
	return e.BlockingReadFn(ctx, base)
}
func (e *EntryConfig) OneShot() bool    { return e.OneShot_ }
func (e *EntryConfig) IsBlocking() bool { return e.IsBlocking_ }
func (e *EntryConfig) Async() bool      { return e.Async_ }

// SyntheticFileInfo implements os.FileInfo for entries with no backing file.
type SyntheticFileInfo struct {
	Name_  string
	Mode_  os.FileMode
	Size_  int64
	IsDir_ bool
}

func (f *SyntheticFileInfo) Name() string       { return f.Name_ }
func (f *SyntheticFileInfo) Size() int64        { return f.Size_ }
func (f *SyntheticFileInfo) Mode() os.FileMode  { return f.Mode_ }
func (f *SyntheticFileInfo) ModTime() time.Time { return time.Time{} }
func (f *SyntheticFileInfo) IsDir() bool        { return f.IsDir_ }
func (f *SyntheticFileInfo) Sys() any           { return nil }

// SyntheticEntry implements os.DirEntry for entries with no backing file.
type SyntheticEntry struct {
	Name_  string
	Mode_  os.FileMode
	IsDir_ bool
}

func (e *SyntheticEntry) Name() string      { return e.Name_ }
func (e *SyntheticEntry) IsDir() bool       { return e.IsDir_ }
func (e *SyntheticEntry) Type() os.FileMode {
	if e.IsDir_ {
		return os.ModeDir
	}
	return 0
}
func (e *SyntheticEntry) Info() (os.FileInfo, error) {
	return &SyntheticFileInfo{Name_: e.Name_, Mode_: e.Mode_, IsDir_: e.IsDir_}, nil
}

// FileEntry returns a synthetic file DirEntry.
func FileEntry(name string, mode os.FileMode) os.DirEntry {
	return &SyntheticEntry{Name_: name, Mode_: mode}
}

// DirEntry returns a synthetic directory DirEntry.
func DirEntry(name string, mode os.FileMode) os.DirEntry {
	return &SyntheticEntry{Name_: name, Mode_: mode, IsDir_: true}
}