//! Nyash PathBox Plugin - minimal path ops (join, dirname, basename, extname, isAbs, normalize)

use once_cell::sync::Lazy;
use std::collections::HashMap;
use std::path::{Path, Component};
use std::sync::{Mutex, atomic::{AtomicU32, Ordering}};

const OK: i32 = 0;
const E_SHORT: i32 = -1;
const E_TYPE: i32 = -2;
const E_METHOD: i32 = -3;
const E_ARGS: i32 = -4;
const E_PLUGIN: i32 = -5;

const M_BIRTH: u32 = 0;        // constructor -> instance
const M_JOIN: u32 = 1;         // join(base, rest) -> string
const M_DIRNAME: u32 = 2;      // dirname(path) -> string
const M_BASENAME: u32 = 3;     // basename(path) -> string
const M_EXTNAME: u32 = 4;      // extname(path) -> string
const M_IS_ABS: u32 = 5;       // isAbs(path) -> bool
const M_NORMALIZE: u32 = 6;    // normalize(path) -> string
const M_FINI: u32 = u32::MAX;  // fini

const TYPE_ID_PATH: u32 = 55;

struct PathInstance; // stateless

static INST: Lazy<Mutex<HashMap<u32, PathInstance>>> = Lazy::new(|| Mutex::new(HashMap::new()));
static NEXT_ID: AtomicU32 = AtomicU32::new(1);

#[no_mangle]
pub extern "C" fn nyash_plugin_abi() -> u32 { 1 }

#[no_mangle]
pub extern "C" fn nyash_plugin_init() -> i32 { OK }

#[no_mangle]
pub extern "C" fn nyash_plugin_invoke(
    type_id: u32,
    method_id: u32,
    instance_id: u32,
    args: *const u8,
    args_len: usize,
    result: *mut u8,
    result_len: *mut usize,
) -> i32 {
    if type_id != TYPE_ID_PATH { return E_TYPE; }
    unsafe {
        match method_id {
            M_BIRTH => {
                if result_len.is_null() { return E_ARGS; }
                if preflight(result, result_len, 4) { return E_SHORT; }
                let id = NEXT_ID.fetch_add(1, Ordering::Relaxed);
                if let Ok(mut m) = INST.lock() { m.insert(id, PathInstance); } else { return E_PLUGIN; }
                let b = id.to_le_bytes(); std::ptr::copy_nonoverlapping(b.as_ptr(), result, 4); *result_len = 4; OK
            }
            M_FINI => { if let Ok(mut m) = INST.lock() { m.remove(&instance_id); OK } else { E_PLUGIN } }
            M_JOIN => {
                let base = match read_arg_string(args, args_len, 0) { Some(s) => s, None => return E_ARGS };
                let rest = match read_arg_string(args, args_len, 1) { Some(s) => s, None => return E_ARGS };
                let joined = if base.ends_with('/') || base.ends_with('\\') { format!("{}{}", base, rest) } else { format!("{}/{}", base, rest) };
                write_tlv_string(&joined, result, result_len)
            }
            M_DIRNAME => {
                let p = match read_arg_string(args, args_len, 0) { Some(s) => s, None => return E_ARGS };
                let d = Path::new(&p).parent().map(|x| x.to_string_lossy().to_string()).unwrap_or_else(|| "".to_string());
                write_tlv_string(&d, result, result_len)
            }
            M_BASENAME => {
                let p = match read_arg_string(args, args_len, 0) { Some(s) => s, None => return E_ARGS };
                let b = Path::new(&p).file_name().map(|x| x.to_string_lossy().to_string()).unwrap_or_else(|| "".to_string());
                write_tlv_string(&b, result, result_len)
            }
            M_EXTNAME => {
                let p = match read_arg_string(args, args_len, 0) { Some(s) => s, None => return E_ARGS };
                let ext = Path::new(&p).extension().map(|x| format!(".{}", x.to_string_lossy())).unwrap_or_else(|| "".to_string());
                write_tlv_string(&ext, result, result_len)
            }
            M_IS_ABS => {
                let p = match read_arg_string(args, args_len, 0) { Some(s) => s, None => return E_ARGS };
                let abs = Path::new(&p).is_absolute() || p.contains(":\\");
                write_tlv_bool(abs, result, result_len)
            }
            M_NORMALIZE => {
                let p = match read_arg_string(args, args_len, 0) { Some(s) => s, None => return E_ARGS };
                let norm = path_clean::PathClean::clean(Path::new(&p));
                write_tlv_string(norm.to_string_lossy().as_ref(), result, result_len)
            }
            _ => E_METHOD,
        }
    }
}

fn preflight(result: *mut u8, result_len: *mut usize, needed: usize) -> bool {
    unsafe { if result_len.is_null() { return false; } if result.is_null() || *result_len < needed { *result_len = needed; return true; } }
    false
}
fn write_tlv_result(payloads: &[(u8, &[u8])], result: *mut u8, result_len: *mut usize) -> i32 {
    if result_len.is_null() { return E_ARGS; }
    let mut buf: Vec<u8> = Vec::with_capacity(4 + payloads.iter().map(|(_,p)| 4 + p.len()).sum::<usize>());
    buf.extend_from_slice(&1u16.to_le_bytes()); buf.extend_from_slice(&(payloads.len() as u16).to_le_bytes());
    for (tag, payload) in payloads { buf.push(*tag); buf.push(0); buf.extend_from_slice(&(payload.len() as u16).to_le_bytes()); buf.extend_from_slice(payload); }
    unsafe { let needed = buf.len(); if result.is_null() || *result_len < needed { *result_len = needed; return E_SHORT; } std::ptr::copy_nonoverlapping(buf.as_ptr(), result, needed); *result_len = needed; }
    OK
}
fn write_tlv_bool(v: bool, result: *mut u8, result_len: *mut usize) -> i32 { write_tlv_result(&[(1u8, &[if v {1u8} else {0u8}])], result, result_len) }
fn write_tlv_string(s: &str, result: *mut u8, result_len: *mut usize) -> i32 { write_tlv_result(&[(6u8, s.as_bytes())], result, result_len) }

fn read_arg_string(args: *const u8, args_len: usize, n: usize) -> Option<String> {
    if args.is_null() || args_len < 4 { return None; }
    let buf = unsafe { std::slice::from_raw_parts(args, args_len) };
    let mut off = 4usize; for i in 0..=n { if buf.len() < off + 4 { return None; } let tag = buf[off]; let size = u16::from_le_bytes([buf[off+2], buf[off+3]]) as usize; if buf.len() < off + 4 + size { return None; } if i == n { if tag == 6 || tag == 7 { return Some(String::from_utf8_lossy(&buf[off+4..off+4+size]).to_string()); } else { return None; } } off += 4 + size; }
    None
}