//! MLua compatibility layer for Roblox Luau.
//!
//! Based on github.com/keplerproject/lua-compat-5.3

use std::ffi::CStr;
use std::mem;
use std::os::raw::{c_char, c_int, c_void};
use std::ptr;

use super::lauxlib::*;
use super::lua::*;
use super::luacode::*;

#[inline(always)]
unsafe fn compat53_reverse(L: *mut lua_State, mut a: c_int, mut b: c_int) {
    while a < b {
        lua_pushvalue(L, a);
        lua_pushvalue(L, b);
        lua_replace(L, a);
        lua_replace(L, b);
        a += 1;
        b -= 1;
    }
}

const COMPAT53_LEVELS1: c_int = 12; // size of the first part of the stack
const COMPAT53_LEVELS2: c_int = 10; // size of the second part of the stack

unsafe fn compat53_findfield(L: *mut lua_State, objidx: c_int, level: c_int) -> c_int {
    if level == 0 || lua_istable(L, -1) == 0 {
        return 0; // not found
    }
    if lua_checkstack(L, 3) == 0 {
        return 0;
    }

    lua_pushnil(L); // start 'next' loop
    while lua_next(L, -2) != 0 {
        // for each pair in table
        if lua_type(L, -2) == LUA_TSTRING {
            // ignore non-string keys
            if lua_rawequal(L, objidx, -1) != 0 {
                // found object?
                lua_pop(L, 1); // remove value (but keep name)
                return 1;
            } else if compat53_findfield(L, objidx, level - 1) != 0 {
                // try recursively
                lua_pushliteral(L, ".");
                lua_replace(L, -2); // remove table (but keep name), place '.' between the two names
                lua_concat(L, 3);
                return 1;
            }
        }
        lua_pop(L, 1); // remove value
    }
    0 // not found
}

unsafe fn compat53_pushglobalfuncname(
    L: *mut lua_State,
    level: c_int,
    ar: &mut lua_Debug,
) -> c_int {
    debug_assert_ne!(lua_checkstack(L, 2), 0);
    let top = lua_gettop(L);
    // push function
    lua_getinfo(L, level, cstr!("f"), ar);
    lua_pushvalue(L, LUA_GLOBALSINDEX);
    if compat53_findfield(L, top + 1, 2) != 0 {
        lua_copy(L, -1, top + 1); // move name to proper place
        lua_pop(L, 2); // remove pushed values
        1
    } else {
        lua_settop(L, top); // remove function and global table
        0
    }
}

unsafe fn compat53_pushfuncname(L: *mut lua_State, level: c_int, ar: &mut lua_Debug) {
    debug_assert_ne!(lua_checkstack(L, 1), 0);
    if !ar.name.is_null() {
        // is there a name?
        lua_pushfstring(L, cstr!("function '%s'"), ar.name);
    } else if compat53_pushglobalfuncname(L, level, ar) != 0 {
        lua_pushfstring(L, cstr!("function '%s'"), lua_tostring(L, -1));
        lua_remove(L, -2); // remove name
    } else {
        lua_pushliteral(L, "?");
    }
}

unsafe fn compat53_pushfuncname_heap(_L: *mut lua_State, _level: c_int, ar: &mut lua_Debug, buf: &mut String) {
    use std::fmt::Write;

    if !ar.name.is_null() {
        // is there a name?
        _ = write!(buf, "function {:?}", CStr::from_ptr(ar.name));
    } else {
        buf.push('?');
    }
}

//
// lua ported functions
//

#[inline(always)]
pub unsafe fn lua_rotate(L: *mut lua_State, mut idx: c_int, mut n: c_int) {
    idx = lua_absindex(L, idx);
    if n > 0 {
        // Faster version
        for _ in 0..n {
            lua_insert(L, idx);
        }
        return;
    }
    let n_elems = lua_gettop(L) - idx + 1;
    if n < 0 {
        n += n_elems;
    }
    if n > 0 && n < n_elems {
        luaL_checkstack(L, 2, cstr!("not enough stack slots available"));
        n = n_elems - n;
        compat53_reverse(L, idx, idx + n - 1);
        compat53_reverse(L, idx + n, idx + n_elems - 1);
        compat53_reverse(L, idx, idx + n_elems - 1);
    }
}

#[inline(always)]
pub unsafe fn lua_copy(L: *mut lua_State, fromidx: c_int, toidx: c_int) {
    let abs_to = lua_absindex(L, toidx);
    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
    lua_pushvalue(L, fromidx);
    lua_replace(L, abs_to);
}

#[inline(always)]
pub unsafe fn lua_isinteger(L: *mut lua_State, idx: c_int) -> c_int {
    if lua_type(L, idx) == LUA_TNUMBER {
        let n = lua_tonumber(L, idx);
        let i = lua_tointeger(L, idx);
        if (n - i as lua_Number).abs() < lua_Number::EPSILON {
            return 1;
        }
    }
    0
}

#[inline(always)]
pub unsafe fn lua_tointeger(L: *mut lua_State, i: c_int) -> lua_Integer {
    lua_tointegerx(L, i, ptr::null_mut())
}

#[inline]
pub unsafe fn lua_tointegerx(L: *mut lua_State, i: c_int, isnum: *mut c_int) -> lua_Integer {
    let mut ok = 0;
    let n = lua_tonumberx(L, i, &mut ok);
    let n_int = n as lua_Integer;
    if ok != 0 && (n - n_int as lua_Number).abs() < lua_Number::EPSILON {
        if !isnum.is_null() {
            *isnum = 1;
        }
        return n_int;
    }
    if !isnum.is_null() {
        *isnum = 0;
    }
    0
}

#[inline(always)]
pub unsafe fn lua_rawlen(L: *mut lua_State, idx: c_int) -> usize {
    lua_objlen(L, idx)
}

#[inline(always)]
pub unsafe fn lua_pushlstring(L: *mut lua_State, s: *const c_char, l: usize) -> *const c_char {
    if l == 0 {
        lua_pushlstring_(L, cstr!(""), 0);
    } else {
        lua_pushlstring_(L, s, l);
    }
    lua_tostring(L, -1)
}

#[inline(always)]
pub unsafe fn lua_pushstring(L: *mut lua_State, s: *const c_char) -> *const c_char {
    lua_pushstring_(L, s);
    lua_tostring(L, -1)
}

#[inline(always)]
pub unsafe fn lua_geti(L: *mut lua_State, mut idx: c_int, n: lua_Integer) -> c_int {
    idx = lua_absindex(L, idx);
    lua_pushinteger(L, n);
    lua_gettable(L, idx)
}

#[inline(always)]
pub unsafe fn lua_rawgeti(L: *mut lua_State, idx: c_int, n: lua_Integer) -> c_int {
    lua_rawgeti_(L, idx, n)
}

#[inline(always)]
pub unsafe fn lua_rawgetp(L: *mut lua_State, idx: c_int, p: *const c_void) -> c_int {
    let abs_i = lua_absindex(L, idx);
    lua_pushlightuserdata(L, p as *mut c_void);
    lua_rawget(L, abs_i)
}

#[inline(always)]
pub unsafe fn lua_getuservalue(L: *mut lua_State, mut idx: c_int) -> c_int {
    luaL_checkstack(L, 2, cstr!("not enough stack slots available"));
    idx = lua_absindex(L, idx);
    lua_pushliteral(L, "__mlua_uservalues");
    if lua_rawget(L, LUA_REGISTRYINDEX) != LUA_TTABLE {
        return LUA_TNIL;
    }
    lua_pushvalue(L, idx);
    lua_rawget(L, -2);
    lua_remove(L, -2);
    lua_type(L, -1)
}

#[inline(always)]
pub unsafe fn lua_seti(L: *mut lua_State, mut idx: c_int, n: lua_Integer) {
    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
    idx = lua_absindex(L, idx);
    lua_pushinteger(L, n);
    lua_insert(L, -2);
    lua_settable(L, idx);
}

#[inline(always)]
pub unsafe fn lua_rawseti(L: *mut lua_State, idx: c_int, n: lua_Integer) {
    lua_rawseti_(L, idx, n)
}

#[inline(always)]
pub unsafe fn lua_rawsetp(L: *mut lua_State, idx: c_int, p: *const c_void) {
    let abs_i = lua_absindex(L, idx);
    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
    lua_pushlightuserdata(L, p as *mut c_void);
    lua_insert(L, -2);
    lua_rawset(L, abs_i);
}

#[inline(always)]
pub unsafe fn lua_setuservalue(L: *mut lua_State, mut idx: c_int) {
    luaL_checkstack(L, 4, cstr!("not enough stack slots available"));
    idx = lua_absindex(L, idx);
    lua_pushliteral(L, "__mlua_uservalues");
    lua_pushvalue(L, -1);
    if lua_rawget(L, LUA_REGISTRYINDEX) != LUA_TTABLE {
        lua_pop(L, 1);
        lua_createtable(L, 0, 2); // main table
        lua_createtable(L, 0, 1); // metatable
        lua_pushliteral(L, "k");
        lua_setfield(L, -2, cstr!("__mode"));
        lua_setmetatable(L, -2);
        lua_pushvalue(L, -2);
        lua_pushvalue(L, -2);
        lua_rawset(L, LUA_REGISTRYINDEX);
    }
    lua_replace(L, -2);
    lua_pushvalue(L, idx);
    lua_pushvalue(L, -3);
    lua_remove(L, -4);
    lua_rawset(L, -3);
    lua_pop(L, 1);
}

#[inline(always)]
pub unsafe fn lua_len(L: *mut lua_State, idx: c_int) {
    match lua_type(L, idx) {
        LUA_TSTRING => {
            lua_pushnumber(L, lua_objlen(L, idx) as lua_Number);
        }
        LUA_TTABLE => {
            if luaL_callmeta(L, idx, cstr!("__len")) == 0 {
                lua_pushnumber(L, lua_objlen(L, idx) as lua_Number);
            }
        }
        LUA_TUSERDATA if luaL_callmeta(L, idx, cstr!("__len")) != 0 => {}
        _ => {
            luaL_error(
                L,
                cstr!("attempt to get length of a %s value"),
                lua_typename(L, lua_type(L, idx)),
            );
        }
    }
}

#[inline(always)]
pub unsafe fn lua_pushglobaltable(L: *mut lua_State) {
    lua_pushvalue(L, LUA_GLOBALSINDEX);
}

#[inline(always)]
pub unsafe fn lua_resume(
    L: *mut lua_State,
    from: *mut lua_State,
    narg: c_int,
    nres: *mut c_int,
) -> c_int {
    let ret = lua_resume_(L, from, narg);
    if (ret == LUA_OK || ret == LUA_YIELD) && !(nres.is_null()) {
        *nres = lua_gettop(L);
    }
    ret
}

//
// lauxlib ported functions
//

#[inline(always)]
pub unsafe fn luaL_checkstack(L: *mut lua_State, sz: c_int, msg: *const c_char) {
    if lua_checkstack(L, sz + LUA_MINSTACK) == 0 {
        if !msg.is_null() {
            luaL_error(L, cstr!("stack overflow (%s)"), msg);
        } else {
            lua_pushliteral(L, "stack overflow");
            lua_error(L);
        }
    }
}

#[inline(always)]
pub unsafe fn luaL_getmetafield(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int {
    if luaL_getmetafield_(L, obj, e) != 0 {
        lua_type(L, -1)
    } else {
        LUA_TNIL
    }
}

#[inline(always)]
pub unsafe fn luaL_newmetatable(L: *mut lua_State, tname: *const c_char) -> c_int {
    if luaL_newmetatable_(L, tname) != 0 {
        lua_pushstring(L, tname);
        lua_setfield(L, -2, cstr!("__name"));
        1
    } else {
        0
    }
}

pub unsafe fn luaL_loadbufferx(
    L: *mut lua_State,
    data: *const c_char,
    mut size: usize,
    name: *const c_char,
    mode: *const c_char,
) -> c_int {
    extern "C" {
        fn free(p: *mut c_void);
    }

    let chunk_is_text = size == 0 || (*data as u8) >= b'\n';
    if !mode.is_null() {
        let modeb = CStr::from_ptr(mode).to_bytes();
        if !chunk_is_text && !modeb.contains(&b'b') {
            lua_pushfstring(
                L,
                cstr!("attempt to load a binary chunk (mode is '%s')"),
                mode,
            );
            return LUA_ERRSYNTAX;
        } else if chunk_is_text && !modeb.contains(&b't') {
            lua_pushfstring(
                L,
                cstr!("attempt to load a text chunk (mode is '%s')"),
                mode,
            );
            return LUA_ERRSYNTAX;
        }
    }

    if chunk_is_text {
        let data = luau_compile_(data, size, ptr::null_mut(), &mut size);
        let ok = luau_load(L, name, data, size, 0) == 0;
        free(data as *mut c_void);
        if !ok {
            return LUA_ERRSYNTAX;
        }
    } else if luau_load(L, name, data, size, 0) != 0 {
        return LUA_ERRSYNTAX;
    }
    LUA_OK
}

#[inline(always)]
pub unsafe fn luaL_loadbuffer(
    L: *mut lua_State,
    data: *const c_char,
    size: usize,
    name: *const c_char,
) -> c_int {
    luaL_loadbufferx(L, data, size, name, ptr::null())
}

#[inline(always)]
pub unsafe fn luaL_len(L: *mut lua_State, idx: c_int) -> lua_Integer {
    let mut isnum = 0;
    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
    lua_len(L, idx);
    let res = lua_tointegerx(L, -1, &mut isnum);
    lua_pop(L, 1);
    if isnum == 0 {
        luaL_error(L, cstr!("object length is not an integer"));
    }
    res
}

// TODO: why not just checkstack and concat all at the end?
pub unsafe fn luaL_traceback(
    L: *mut lua_State,
    L1: *mut lua_State,
    msg: *const c_char,
    mut level: c_int,
) {
    let mut ar: lua_Debug = mem::zeroed();
    let top = lua_gettop(L);
    let numlevels = lua_stackdepth(L);
    let mark = if numlevels > COMPAT53_LEVELS1 + COMPAT53_LEVELS2 {
        COMPAT53_LEVELS1
    } else {
        0
    };

    debug_assert_ne!(lua_checkstack(L, 1), 0);

    //let stack_req = if msg.is_null() { 0 } else { 1 } + 4 * (mark+1);
    let stack_req = if msg.is_null() { 0 } else { 1 } + 4;

    if lua_checkstack(L, stack_req) == 0 {
        lua_pushliteral(L, "[not enough stack space]");
        return;
    }

    if !msg.is_null() {
        lua_pushfstring(L, cstr!("%s\n"), msg);
    }

    lua_pushliteral(L, "stack traceback:");

    while lua_getinfo(L1, level, cstr!(""), &mut ar) != 0 {
        if level + 1 == mark {
            // too many levels?
            lua_pushliteral(L, "\n\t..."); // add a '...'
            level = numlevels - COMPAT53_LEVELS2; // and skip to last ones
        } else {
            lua_getinfo(L1, level, cstr!("sln"), &mut ar);
            lua_pushfstring(L, cstr!("\n\t%s:"), ar.short_src);
            if ar.currentline > 0 {
                lua_pushfstring(L, cstr!("%d:"), ar.currentline);
            }
            lua_pushliteral(L, " in ");
            compat53_pushfuncname(L, level, &mut ar);
            lua_concat(L, lua_gettop(L) - top);
        }
        level += 1;
    }
    lua_concat(L, lua_gettop(L) - top);
}

pub unsafe fn luaL_traceback_heap(
    L: *mut lua_State,
    L1: *mut lua_State,
    msg: Option<String>,
    mut level: c_int,
) -> String {
    use std::fmt::Write;

    let mut ar: lua_Debug = mem::zeroed();
    let numlevels = lua_stackdepth(L);
    let mark = if numlevels > COMPAT53_LEVELS1 + COMPAT53_LEVELS2 {
        COMPAT53_LEVELS1
    } else {
        0
    };

    let mut buf = msg.unwrap_or_default();
    if !buf.is_empty() {
        buf.push('\n');
    }
    buf.push_str("stack traceback:");
    while lua_getinfo(L1, level, cstr!(""), &mut ar) != 0 {
        if level + 1 == mark {
            // too many levels?
            buf.push_str("\n\t..."); // add a '...'
            level = numlevels - COMPAT53_LEVELS2; // and skip to last ones
        } else {
            lua_getinfo(L1, level, cstr!("sln"), &mut ar);
            let src = CStr::from_ptr(ar.short_src);
            if let Ok(src) = src.to_str() {
                _  = write!(buf, "\n\t{}:", src);
            } else {
                _  = write!(buf, "\n\t{:?}:", src);
            }
            if ar.currentline > 0 {
                _ = write!(buf, "{}:", ar.currentline);
            }
            buf.push_str(" in ");
            compat53_pushfuncname_heap(L, level, &mut ar, &mut buf);
        }
        level += 1;
    }
    buf
}

pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize) -> *const c_char {
    idx = lua_absindex(L, idx);
    if luaL_callmeta(L, idx, cstr!("__tostring")) == 0 {
        match lua_type(L, idx) {
            LUA_TNIL => {
                lua_pushliteral(L, "nil");
            }
            LUA_TSTRING | LUA_TNUMBER => {
                lua_pushvalue(L, idx);
            }
            LUA_TBOOLEAN => {
                if lua_toboolean(L, idx) == 0 {
                    lua_pushliteral(L, "false");
                } else {
                    lua_pushliteral(L, "true");
                }
            }
            t => {
                let tt = luaL_getmetafield(L, idx, cstr!("__name"));
                let name = if tt == LUA_TSTRING {
                    lua_tostring(L, -1)
                } else {
                    lua_typename(L, t)
                };
                lua_pushfstring(L, cstr!("%s: %p"), name, lua_topointer(L, idx));
                if tt != LUA_TNIL {
                    lua_replace(L, -2); // remove '__name'
                }
            }
        };
    } else if lua_isstring(L, -1) == 0 {
        luaL_error(L, cstr!("'__tostring' must return a string"));
    }
    lua_tolstring(L, -1, len)
}

#[inline(always)]
pub unsafe fn luaL_setmetatable(L: *mut lua_State, tname: *const c_char) {
    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
    luaL_getmetatable(L, tname);
    lua_setmetatable(L, -2);
}

pub unsafe fn luaL_getsubtable(L: *mut lua_State, idx: c_int, fname: *const c_char) -> c_int {
    let abs_i = lua_absindex(L, idx);
    luaL_checkstack(L, 3, cstr!("not enough stack slots"));
    lua_pushstring_(L, fname);
    if lua_gettable(L, abs_i) == LUA_TTABLE {
        return 1;
    }
    lua_pop(L, 1);
    lua_newtable(L);
    lua_pushstring_(L, fname);
    lua_pushvalue(L, -2);
    lua_settable(L, abs_i);
    0
}

pub unsafe fn luaL_requiref(
    L: *mut lua_State,
    modname: *const c_char,
    openf: lua_CFunction,
    glb: c_int,
) {
    luaL_checkstack(L, 3, cstr!("not enough stack slots available"));
    luaL_getsubtable(L, LUA_REGISTRYINDEX, cstr!("_LOADED"));
    if lua_getfield(L, -1, modname) == LUA_TNIL {
        lua_pop(L, 1);
        lua_pushcfunction(L, openf, b"open\0".as_ptr().cast());
        lua_pushstring(L, modname);
        lua_call(L, 1, 1);
        lua_pushvalue(L, -1);
        lua_setfield(L, -3, modname);
    }
    if glb != 0 {
        lua_pushvalue(L, -1);
        lua_setglobal(L, modname);
    } else {
        lua_pushnil(L);
        lua_setglobal(L, modname);
    }
    lua_replace(L, -2);
}