// Package main builds the C ABI used by the KDE integration.
// Build with: go build -buildmode=c-shared -o libollie9p.so
//
// The shared 9P client implementation lives in ollie/client.
package main

/*
#include <stdlib.h>
#include <string.h>
*/
import "C"

import (
	"fmt"
	"io"
	"os"
	"strings"
	"sync"
	"unsafe"

	"9fans.net/go/plan9"
	p9client "9fans.net/go/plan9/client"
)

// Connection handle - opaque to C callers
type connHandle struct {
	fsys *p9client.Fsys
}

// File handle - for streaming reads
type fidHandle struct {
	conn   C.int // parent connection handle
	reader io.ReadCloser
}

var (
	handleMu   sync.Mutex
	handles          = make(map[C.int]*connHandle)
	nextHandle C.int = 1

	fidMu   sync.Mutex
	fids          = make(map[C.int]*fidHandle)
	nextFid C.int = 1
)

func allocHandle(h *connHandle) C.int {
	handleMu.Lock()
	defer handleMu.Unlock()
	id := nextHandle
	nextHandle++
	handles[id] = h
	return id
}

func getHandle(id C.int) *connHandle {
	handleMu.Lock()
	defer handleMu.Unlock()
	return handles[id]
}

func freeHandle(id C.int) {
	handleMu.Lock()
	defer handleMu.Unlock()
	delete(handles, id)
}

func allocFid(f *fidHandle) C.int {
	fidMu.Lock()
	defer fidMu.Unlock()
	id := nextFid
	nextFid++
	fids[id] = f
	return id
}

func getFid(id C.int) *fidHandle {
	fidMu.Lock()
	defer fidMu.Unlock()
	return fids[id]
}

func freeFid(id C.int) {
	fidMu.Lock()
	defer fidMu.Unlock()
	delete(fids, id)
}

// Error handling - last error per thread (simplified: global for now)
var lastError string
var lastErrMu sync.Mutex

func setError(err error) {
	lastErrMu.Lock()
	if err != nil {
		lastError = err.Error()
	} else {
		lastError = ""
	}
	lastErrMu.Unlock()
}

//export ollie9p_last_error
func ollie9p_last_error() *C.char {
	lastErrMu.Lock()
	defer lastErrMu.Unlock()
	if lastError == "" {
		return nil
	}
	return C.CString(lastError)
}

//export ollie9p_free
func ollie9p_free(ptr unsafe.Pointer) {
	C.free(ptr)
}

// ollie9p_connect establishes a connection to the 9P server.
// addr: socket path (e.g., "/tmp/ns.user.:0/ollie") or "tcp!host:port"
// user: username for Tauth/Tattach
// aname: attach name (identity for permissions)
// Returns: handle > 0 on success, -1 on error (call ollie9p_last_error)
//
//export ollie9p_connect
func ollie9p_connect(addr *C.char, user *C.char, aname *C.char) C.int {
	goAddr := C.GoString(addr)
	goUser := C.GoString(user)
	goAname := C.GoString(aname)

	conn, err := dial(goAddr)
	if err != nil {
		setError(err)
		return -1
	}
	fsys, err := conn.Attach(nil, goUser, goAname)
	if err != nil {
		conn.Close()
		setError(err)
		return -1
	}

	h := &connHandle{fsys: fsys}
	setError(nil)
	return allocHandle(h)
}

// ollie9p_connect_default connects using NAMESPACE and USER env vars.
// Returns: handle > 0 on success, -1 on error
//
//export ollie9p_connect_default
func ollie9p_connect_default() C.int {
	fsys, err := dialDefault()
	if err != nil {
		setError(err)
		return -1
	}

	h := &connHandle{fsys: fsys}
	setError(nil)
	return allocHandle(h)
}

//export ollie9p_close
func ollie9p_close(handle C.int) {
	h := getHandle(handle)
	if h == nil {
		return
	}
	if h.fsys != nil {
		h.fsys.Close()
	}
	freeHandle(handle)
}

// ollie9p_read reads a file's contents.
// Returns: newly allocated buffer (caller must ollie9p_free), NULL on error.
// outLen receives the length of returned data.
//
//export ollie9p_read
func ollie9p_read(handle C.int, path *C.char, outLen *C.int) *C.char {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return nil
	}

	data, err := readFile(h.fsys, C.GoString(path))
	if err != nil {
		setError(err)
		return nil
	}

	setError(nil)
	*outLen = C.int(len(data))
	if len(data) == 0 {
		return C.CString("")
	}
	cdata := C.CString(string(data))
	return cdata
}

// ollie9p_read_bytes reads a file into a caller-provided buffer.
// Returns: bytes read, or -1 on error.
//
//export ollie9p_read_bytes
func ollie9p_read_bytes(handle C.int, path *C.char, buf *C.char, bufLen C.int) C.int {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return -1
	}

	data, err := readFile(h.fsys, C.GoString(path))
	if err != nil {
		setError(err)
		return -1
	}

	n := int(bufLen)
	if n > len(data) {
		n = len(data)
	}
	goBuf := unsafe.Slice((*byte)(unsafe.Pointer(buf)), n)
	copy(goBuf, data[:n])

	setError(nil)
	return C.int(n)
}

// ollie9p_write writes data to a file.
// Returns: bytes written, or -1 on error.
//
//export ollie9p_write
func ollie9p_write(handle C.int, path *C.char, data *C.char, dataLen C.int) C.int {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return -1
	}

	goData := C.GoBytes(unsafe.Pointer(data), dataLen)
	if err := writeFile(h.fsys, C.GoString(path), goData); err != nil {
		setError(err)
		return -1
	}

	setError(nil)
	return C.int(len(goData))
}

// ollie9p_rdwr performs write-then-read on a request/response file.
// Returns: newly allocated response buffer, NULL on error.
//
//export ollie9p_rdwr
func ollie9p_rdwr(handle C.int, path *C.char, data *C.char, dataLen C.int, outLen *C.int) *C.char {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return nil
	}

	goData := C.GoBytes(unsafe.Pointer(data), dataLen)
	resp, err := rdwr(h.fsys, C.GoString(path), goData)
	if err != nil {
		setError(err)
		return nil
	}

	setError(nil)
	*outLen = C.int(len(resp))
	return C.CString(string(resp))
}

// ollie9p_stat returns file metadata as "mode\tsize\tmtime\tname\n"
// Returns: newly allocated string, NULL on error.
//
//export ollie9p_stat
func ollie9p_stat(handle C.int, path *C.char) *C.char {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return nil
	}

	dir, err := h.fsys.Stat(C.GoString(path))
	if err != nil {
		setError(err)
		return nil
	}

	setError(nil)
	result := strings.Join([]string{
		modeString(dir.Mode),
		itoa(int64(dir.Length)),
		itoa(int64(dir.Mtime)),
		dir.Name,
	}, "\t")
	return C.CString(result)
}

// ollie9p_ls lists directory contents.
// Returns: newline-separated names, NULL on error.
//
//export ollie9p_ls
func ollie9p_ls(handle C.int, path *C.char) *C.char {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return nil
	}

	names, err := listDir(h.fsys, C.GoString(path))
	if err != nil {
		setError(err)
		return nil
	}

	setError(nil)
	return C.CString(strings.Join(names, "\n"))
}

// ollie9p_remove removes a file.
// Returns: 0 on success, -1 on error.
//
//export ollie9p_remove
func ollie9p_remove(handle C.int, path *C.char) C.int {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return -1
	}

	if err := h.fsys.Remove(C.GoString(path)); err != nil {
		setError(err)
		return -1
	}

	setError(nil)
	return 0
}

// ollie9p_create creates a file.
// Returns: 0 on success, -1 on error.
//
//export ollie9p_create
func ollie9p_create(handle C.int, path *C.char, perm C.uint) C.int {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return -1
	}

	if err := create(h.fsys, C.GoString(path), plan9.Perm(perm)); err != nil {
		setError(err)
		return -1
	}

	setError(nil)
	return 0
}

// ollie9p_mkdir creates a directory.
// Returns: 0 on success, -1 on error.
//
//export ollie9p_mkdir
func ollie9p_mkdir(handle C.int, path *C.char) C.int {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return -1
	}

	if err := mkdir(h.fsys, C.GoString(path)); err != nil {
		setError(err)
		return -1
	}

	setError(nil)
	return 0
}

// ollie9p_rename renames a file (Twstat).
// Returns: 0 on success, -1 on error.
//
//export ollie9p_rename
func ollie9p_rename(handle C.int, oldPath *C.char, newName *C.char) C.int {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return -1
	}

	if err := h.fsys.Wstat(C.GoString(oldPath), &plan9.Dir{Name: C.GoString(newName)}); err != nil {
		setError(err)
		return -1
	}

	setError(nil)
	return 0
}

// --- Streaming API ---

// ollie9p_open opens a file for streaming reads.
// Returns: fid handle > 0 on success, -1 on error.
// The fid must be closed with ollie9p_close_fid.
//
//export ollie9p_open
func ollie9p_open(handle C.int, path *C.char) C.int {
	h := getHandle(handle)
	if h == nil {
		setError(&errString{"invalid handle"})
		return -1
	}

	reader, err := h.fsys.Open(C.GoString(path), plan9.OREAD)
	if err != nil {
		setError(err)
		return -1
	}

	fid := &fidHandle{
		conn:   handle,
		reader: reader,
	}
	setError(nil)
	return allocFid(fid)
}

// ollie9p_read_fid reads from an open file into a buffer.
// Returns: bytes read (0 on EOF), -1 on error.
// Blocks until data is available or EOF.
//
//export ollie9p_read_fid
func ollie9p_read_fid(fid C.int, buf *C.char, bufLen C.int) C.int {
	f := getFid(fid)
	if f == nil {
		setError(&errString{"invalid fid"})
		return -1
	}

	goBuf := unsafe.Slice((*byte)(unsafe.Pointer(buf)), int(bufLen))
	n, err := f.reader.Read(goBuf)
	if err != nil {
		if err == io.EOF {
			setError(nil)
			return 0
		}
		setError(err)
		return -1
	}

	setError(nil)
	return C.int(n)
}

// ollie9p_close_fid closes an open file handle.
//
//export ollie9p_close_fid
func ollie9p_close_fid(fid C.int) {
	f := getFid(fid)
	if f == nil {
		return
	}
	if f.reader != nil {
		f.reader.Close()
	}
	freeFid(fid)
}

func dial(address string) (*p9client.Conn, error) {
	network := "unix"
	dialAddr := address
	if strings.HasPrefix(address, "tcp!") {
		network = "tcp"
		dialAddr = strings.TrimPrefix(address, "tcp!")
	} else if strings.HasPrefix(address, "unix!") {
		dialAddr = strings.TrimPrefix(address, "unix!")
	} else if strings.Contains(address, ":") && !strings.HasPrefix(address, "/") {
		network = "tcp"
	}
	return p9client.Dial(network, dialAddr)
}

func dialDefault() (*p9client.Fsys, error) {
	ns := os.Getenv("NAMESPACE")
	if ns == "" {
		ns = p9client.Namespace()
	}
	if ns == "" {
		return nil, fmt.Errorf("cannot determine namespace")
	}
	user := os.Getenv("USER")
	if user == "" {
		user = "none"
	}
	aname := os.Getenv("OLLIE_UNAME")
	if aname == "" {
		aname = user
	}
	conn, err := dial(ns + "/ollie")
	if err != nil {
		return nil, err
	}
	fsys, err := conn.Attach(nil, user, aname)
	if err != nil {
		conn.Close()
		return nil, err
	}
	return fsys, nil
}

func readFile(fsys *p9client.Fsys, path string) ([]byte, error) {
	fid, err := fsys.Open(path, plan9.OREAD)
	if err != nil {
		return nil, err
	}
	defer fid.Close()
	return io.ReadAll(fid)
}

func writeFile(fsys *p9client.Fsys, path string, data []byte) error {
	fid, err := fsys.Open(path, plan9.OWRITE)
	if err != nil {
		return err
	}
	if _, err := fid.Write(data); err != nil {
		fid.Close()
		return err
	}
	return fid.Close()
}

func rdwr(fsys *p9client.Fsys, path string, data []byte) ([]byte, error) {
	fid, err := fsys.Open(path, plan9.ORDWR)
	if err != nil {
		return nil, err
	}
	if _, err := fid.Write(data); err != nil {
		fid.Close()
		return nil, err
	}
	if _, err := fid.Seek(0, 0); err != nil {
		fid.Close()
		return nil, err
	}
	result, err := io.ReadAll(fid)
	closeErr := fid.Close()
	if err != nil {
		return nil, err
	}
	return result, closeErr
}

func create(fsys *p9client.Fsys, path string, perm plan9.Perm) error {
	fid, err := fsys.Create(path, plan9.OWRITE, perm)
	if err != nil {
		return err
	}
	return fid.Close()
}

func mkdir(fsys *p9client.Fsys, path string) error {
	fid, err := fsys.Create(path, plan9.OREAD, plan9.DMDIR|0755)
	if err != nil {
		return err
	}
	return fid.Close()
}

func listDir(fsys *p9client.Fsys, path string) ([]string, error) {
	fid, err := fsys.Open(path, plan9.OREAD)
	if err != nil {
		return nil, err
	}
	dirs, err := fid.Dirreadall()
	fid.Close()
	if err != nil {
		return nil, err
	}
	names := make([]string, len(dirs))
	for i, dir := range dirs {
		names[i] = dir.Name
	}
	return names, nil
}

func modeString(mode plan9.Perm) string {
	var buf [10]byte
	if mode&plan9.DMDIR != 0 {
		buf[0] = 'd'
	} else {
		buf[0] = '-'
	}
	const rwx = "rwx"
	for i := 0; i < 3; i++ {
		for j := 0; j < 3; j++ {
			if mode&(1<<uint(8-i*3-j)) != 0 {
				buf[1+i*3+j] = rwx[j]
			} else {
				buf[1+i*3+j] = '-'
			}
		}
	}
	return string(buf[:])
}

// Helper types
type errString struct{ s string }

func (e *errString) Error() string { return e.s }

func itoa(n int64) string {
	if n == 0 {
		return "0"
	}
	var buf [20]byte
	i := len(buf)
	neg := n < 0
	if neg {
		n = -n
	}
	for n > 0 {
		i--
		buf[i] = byte('0' + n%10)
		n /= 10
	}
	if neg {
		i--
		buf[i] = '-'
	}
	return string(buf[i:])
}

func main() {}