use oxide_kernel::shape_forge::EMPTY_SHAPE_ID;
use oxide_types::object::{JsObject, NativeFnPtr};
use oxide_types::value::JsValue;

use oxide_runtime_api::{NativeResult, VmHost};

fn get_regexp_ptr<H: VmHost>(vm: &mut H, args: &[u8]) -> Result<*mut JsObject, JsValue> {
    let this_val = vm.reg(args[0]);
    if !this_val.is_object() {
        return Err(crate::error::create_type_error(vm, "RegExp.prototype method called on non-object"));
    }
    let ptr = this_val.as_js_object_ptr();
    if ptr.is_null() {
        return Err(crate::error::create_type_error(vm, "null object"));
    }
    if !unsafe { &*ptr }.is_regexp_obj() {
        return Err(crate::error::create_type_error(vm, "RegExp.prototype method called on non-RegExp object"));
    }
    Ok(ptr)
}

fn parse_flags(flags: &str) -> (bool, bool, bool, bool, bool, bool, bool) {
    let mut global = false;
    let mut ignore_case = false;
    let mut multi_line = false;
    let mut dot_all = false;
    let mut sticky = false;
    let mut unicode = false;
    let mut has_indices = false;
    for c in flags.chars() {
        match c {
            'g' => global = true,
            'i' => ignore_case = true,
            'm' => multi_line = true,
            's' => dot_all = true,
            'y' => sticky = true,
            'u' => unicode = true,
            'd' => has_indices = true,
            _ => {}
        }
    }
    (global, ignore_case, multi_line, dot_all, sticky, unicode, has_indices)
}

fn set_prop<H: VmHost>(obj: &mut JsObject, name: &str, val: JsValue, vm: &H) {
    let si = vm.kernel_core().perm_interner().intern(name).0;
    set_prop_by_si(obj, si, val, vm);
}

fn set_prop_by_si<H: VmHost>(obj: &mut JsObject, prop_name_si: u32, val: JsValue, vm: &H) {
    let shape_id = vm.kernel_core().shape_forge().make_shape(obj.shape_id(), prop_name_si);
    obj.set_shape_id(shape_id);
    obj.ensure_hash_props().push(val);
}

fn get_prop(obj: &JsObject, idx: usize) -> JsValue {
    obj.hash_props_vec()
        .and_then(|v| v.get(idx))
        .copied()
        .unwrap_or(JsValue::undefined())
}

fn set_prop_at(obj: *mut JsObject, idx: usize, val: JsValue) {
    unsafe {
        let re = &mut *obj;
        if let Some(vec) = re.hash_props_vec() {
            let ptr = vec.as_ptr() as *mut JsValue;
            let v = &mut *ptr.add(idx);
            *v = val;
        }
    }
}

/// `RegExp(pattern, flags)` 构造逻辑：用 regress 引擎编译模式（ECMAScript 语法，
/// 支持 backreference/lookaround/命名组/v-flag）；非法模式抛 SyntaxError。
/// 编译结果存于对象的 native_fn 槽。
pub fn regexp_constructor<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let (pattern, flags) = if args.len() < 2 {
        (String::new(), String::new())
    } else if args.len() < 3 {
        let pat = oxide_runtime_api::to_string(vm.reg(args[1]));
        (pat, String::new())
    } else {
        let pat = oxide_runtime_api::to_string(vm.reg(args[1]));
        let fl = oxide_runtime_api::to_string(vm.reg(args[2]));
        (pat, fl)
    };

    let (global, ignore_case, multi_line, dot_all, sticky, unicode, has_indices) = parse_flags(&flags);

    let mut obj = JsObject::new_empty(
        EMPTY_SHAPE_ID,
        JsValue::from_js_object(vm.session().builtin_world().regexp_proto.as_ptr() as *mut JsObject),
    );

    // regress 用 JS flag 字符串编译：g/i/m/s/u/y 原样透传（v 由调用方映射为 u+set 语义）。
    let compiled = regress::Regex::with_flags(&pattern, flags.as_str());

    match compiled {
        Ok(re) => {
            let re_ptr = Box::into_raw(Box::new(re));
            // SAFETY: re_ptr 是构造器经 `NativeFnPtr::from_raw(re_ptr as *const ())`
            // 写入的 `Box<regress::Regex>` 指针。RegExp 对象把 native_fn 字段复用作
            // 已编译 Regex 的存放处——而非 NativeFn 指针。对象存活期间有效；
            // VM 重置经 `drop_regexp_native` 释放该 Box。
            obj.set_native_fn(Some(unsafe { NativeFnPtr::from_raw(re_ptr as *const ()) }));
        }
        Err(e) => {
            return NativeResult::Err(crate::error::create_syntax_error(
                vm,
                &format!("Invalid regular expression: {e}"),
            ));
        }
    }

    set_prop(&mut obj, "lastIndex", JsValue::int(0), vm);
    set_prop(&mut obj, "source", vm.new_string(&pattern), vm);
    set_prop(&mut obj, "flags", vm.new_string(&flags), vm);
    set_prop(&mut obj, "global", JsValue::bool(global), vm);
    set_prop(&mut obj, "ignoreCase", JsValue::bool(ignore_case), vm);
    set_prop(&mut obj, "multiline", JsValue::bool(multi_line), vm);
    set_prop(&mut obj, "dotAll", JsValue::bool(dot_all), vm);
    set_prop(&mut obj, "sticky", JsValue::bool(sticky), vm);
    set_prop(&mut obj, "unicode", JsValue::bool(unicode), vm);
    set_prop(&mut obj, "hasIndices", JsValue::bool(has_indices), vm);
    obj.type_tag = JsObject::OBJ_TYPE_REGEXP;

    let obj_ptr = vm.alloc_object(obj);
    NativeResult::Ok(JsValue::from_js_object(obj_ptr))
}

/// 释放 RegExp 对象 native_fn 槽中编译的 `regress::Regex`，返回释放字节数。
pub fn drop_regexp_native(obj: &mut JsObject) -> u64 {
    if !obj.is_regexp_obj() {
        return 0;
    }
    let Some(ptr) = obj.native_fn() else {
        return 0;
    };
    let regex_ptr = ptr.as_ptr() as *mut regress::Regex;
    if regex_ptr.is_null() {
        return 0;
    }
    unsafe { drop(Box::from_raw(regex_ptr)) };
    obj.set_native_fn(None);
    std::mem::size_of::<regress::Regex>() as u64
}

/// `RegExp.prototype.test(string)`：判断是否匹配。global 模式下从 lastIndex 开始匹配。
pub fn regexp_test<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let re_ptr = match get_regexp_ptr(vm, args) {
        Ok(ptr) => ptr,
        Err(err) => return NativeResult::Err(err),
    };
    let re = unsafe { &*re_ptr };

    let fn_ptr = match re.native_fn() {
        None => {
            return NativeResult::Err(crate::error::create_type_error(vm, "invalid RegExp"));
        }
        Some(p) => p,
    };

    // SAFETY: fn_ptr 持有 regexp_constructor 存放的 `Box<regress::Regex>` 指针。
    let regex = unsafe { &*(fn_ptr.as_ptr() as *const regress::Regex) };
    let haystack = match regexp_string_arg(vm, args) {
        Ok(s) => s,
        Err(err) => return NativeResult::Err(err),
    };
    let last_index = vm.coerce_number_bounded(get_prop(re, 0)).unwrap_or(f64::NAN) as usize;
    let is_global = is_global(re);

    if is_global {
        let result = regex.find_from(&haystack, last_index).next().is_some();
        NativeResult::Ok(JsValue::bool(result))
    } else {
        NativeResult::Ok(JsValue::bool(regex.find(&haystack).is_some()))
    }
}

/// `RegExp.prototype.exec(string)`：执行匹配并返回数组（含捕获组、index、input）。
/// 无匹配返回 null；global 模式推进/重置 lastIndex。
pub fn regexp_exec<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let re_ptr = match get_regexp_ptr(vm, args) {
        Ok(ptr) => ptr,
        Err(err) => return NativeResult::Err(err),
    };

    let fn_ptr = {
        let re = unsafe { &*re_ptr };
        match re.native_fn() {
            None => {
                return NativeResult::Err(crate::error::create_type_error(vm, "invalid RegExp"));
            }
            Some(p) => p,
        }
    };

    // SAFETY: fn_ptr 持有 regexp_constructor 存放的 `Box<regress::Regex>` 指针。
    let regex = unsafe { &*(fn_ptr.as_ptr() as *const regress::Regex) };
    let haystack = match regexp_string_arg(vm, args) {
        Ok(s) => s,
        Err(err) => return NativeResult::Err(err),
    };

    let (last_index, is_global) = {
        let re = unsafe { &*re_ptr };
        let li = vm.coerce_number_bounded(get_prop(re, 0)).unwrap_or(f64::NAN) as usize;
        let g = is_global(re);
        (li, g)
    };

    let match_result = if is_global {
        if last_index > haystack.len() {
            return NativeResult::Ok(JsValue::null());
        }
        regex.find_from(&haystack, last_index).next()
    } else {
        regex.find(&haystack)
    };

    if let Some(m) = match_result {
        let range = m.range();
        let group_count = m.captures.len();
        let n = 1 + group_count;
        let proto = vm.session().builtin_world().array_proto.as_ptr() as *mut JsObject;
        let arr =
            vm.epoch()
                .alloc(JsObject::new_array(EMPTY_SHAPE_ID, JsValue::from_js_object(proto), n, vm.epoch().bump()));
        unsafe {
            (*arr).set_prop_at(0, vm.new_string(&haystack[range.start..range.end]));
            // 捕获组：未参与匹配的组为 undefined。
            for i in 1..=group_count {
                match m.group(i) {
                    Some(g) => (*arr).set_prop_at(i, vm.new_string(&haystack[g.start..g.end])),
                    None => (*arr).set_prop_at(i, JsValue::undefined()),
                }
            }
            (*arr).set_prop_count(n);
        }

        let index_si = vm.kernel_core().perm_interner().intern("index").0;
        vm.set_or_create_prop_value(unsafe { &mut *arr }, index_si, JsValue::int(range.start as i32));
        let input_si = vm.kernel_core().perm_interner().intern("input").0;
        let haystack_val = vm.new_string(&haystack);
        vm.set_or_create_prop_value(unsafe { &mut *arr }, input_si, haystack_val);
        let groups_si = vm.kernel_core().perm_interner().intern("groups").0;
        vm.set_or_create_prop_value(unsafe { &mut *arr }, groups_si, JsValue::undefined());
        if is_global {
            set_prop_at(re_ptr, 0, JsValue::int(range.end as i32));
        }

        NativeResult::Ok(JsValue::from_js_object(arr))
    } else {
        if is_global {
            set_prop_at(re_ptr, 0, JsValue::int(0));
        }
        NativeResult::Ok(JsValue::null())
    }
}

/// `RegExp.prototype.toString`：按 `/source/flags` 形式返回。
pub fn regexp_to_string<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let re_ptr = match get_regexp_ptr(vm, args) {
        Ok(ptr) => ptr,
        Err(err) => return NativeResult::Err(err),
    };
    let re = unsafe { &*re_ptr };
    let source = {
        let val = get_prop(re, 1);
        vm.lookup_str(val).unwrap_or_default()
    };
    let flags = {
        let val = get_prop(re, 2);
        vm.lookup_str(val).unwrap_or_default()
    };
    let result = format!("/{}/{}", source, flags);
    NativeResult::Ok(vm.new_string(&result))
}

// RegExp 对象 hash 槽中属性的固定下标（构造顺序：lastIndex/source/flags/global/...）。
const PROP_LAST_INDEX: usize = 0;
const PROP_SOURCE: usize = 1;
const PROP_FLAGS: usize = 2;
const PROP_GLOBAL: usize = 3;

/// 读 global 标志；槽值被 accessor 重定义后不再保证是 bool，非 bool 一律视为 false。
fn is_global(re: &JsObject) -> bool {
    match get_prop(re, PROP_GLOBAL) {
        v if v.is_bool() => v.as_bool(),
        _ => false,
    }
}

/// 取 this 的已编译 regress 正则与匹配文本；this 非 RegExp 或缺失编译结果时返回 Err。
fn regexp_regex_and_text<H: VmHost>(vm: &mut H, args: &[u8]) -> Result<(&'static regress::Regex, String), JsValue> {
    let re_ptr = get_regexp_ptr(vm, args)?;
    let fn_ptr = {
        let re = unsafe { &*re_ptr };
        match re.native_fn() {
            None => return Err(crate::error::create_type_error(vm, "invalid RegExp")),
            Some(p) => p,
        }
    };
    // SAFETY: fn_ptr 持有 regexp_constructor 存放的 `Box<regress::Regex>` 指针。
    let regex = unsafe { &*(fn_ptr.as_ptr() as *const regress::Regex) };
    let haystack = regexp_string_arg(vm, args)?;
    Ok((regex, haystack))
}

/// 取匹配文本参数，按 ToString 语义完整转换（对象经 toString/valueOf）；异常原样传播。
fn regexp_string_arg<H: VmHost>(vm: &mut H, args: &[u8]) -> Result<String, JsValue> {
    let val = vm.reg(if args.len() > 1 { args[1] } else { args[0] });
    match oxide_runtime_api::to_string_full(val, vm) {
        Ok(s) => Ok(s),
        Err(_) => {
            // ToString 触发对象 toString/valueOf 抛出的原生异常须原样传播。
            if let Some(exc) = vm.take_uncaught_value() {
                return Err(exc);
            }
            Err(crate::error::create_type_error(vm, "Cannot convert value to a string"))
        }
    }
}

/// `RegExp.prototype[Symbol.match](string)`：global 正则收集全部匹配串，
/// 非 global 返回单个 exec 匹配数组；无匹配返回 null。
///
/// # 步骤
/// 1. 非 global：直接复用 exec 结果（数组含 index/input/groups）。
/// 2. global：lastIndex 归零后逐匹配收集完整匹配串，末次匹配后推进 lastIndex。
pub fn regexp_symbol_match<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let re_ptr = match get_regexp_ptr(vm, args) {
        Ok(ptr) => ptr,
        Err(err) => return NativeResult::Err(err),
    };
    let is_global = is_global(unsafe { &*re_ptr });
    if !is_global {
        return regexp_exec(vm, args);
    }

    let (regex, haystack) = match regexp_regex_and_text(vm, args) {
        Ok(pair) => pair,
        Err(err) => return NativeResult::Err(err),
    };
    set_prop_at(re_ptr, PROP_LAST_INDEX, JsValue::int(0));
    let mut matches: Vec<String> = Vec::new();
    let mut last_end = 0;
    for m in regex.find_iter(&haystack) {
        let range = m.range();
        matches.push(haystack[range.start..range.end].to_string());
        last_end = range.end;
    }
    set_prop_at(re_ptr, PROP_LAST_INDEX, JsValue::int(last_end as i32));
    if matches.is_empty() {
        return NativeResult::Ok(JsValue::null());
    }
    NativeResult::Ok(crate::string::make_string_array(vm, &matches))
}

/// `RegExp.prototype[Symbol.replace](string, replacement)`：按匹配替换。
/// 字符串 replacement 展开 `$` 引用（`$$`/`$&`/``$` ``/`$'`/`$n`），函数 replacement
/// 逐匹配调用；global 全替换，否则替换首个。
///
/// # 步骤
/// 1. global 时 lastIndex 归零，复用 string 模块的替换逻辑。
/// 2. 结束后把 lastIndex 推进到末次匹配末尾（无匹配保持 0）。
pub fn regexp_symbol_replace<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let re_ptr = match get_regexp_ptr(vm, args) {
        Ok(ptr) => ptr,
        Err(err) => return NativeResult::Err(err),
    };
    let is_global = is_global(unsafe { &*re_ptr });
    let (regex, haystack) = match regexp_regex_and_text(vm, args) {
        Ok(pair) => pair,
        Err(err) => return NativeResult::Err(err),
    };
    if is_global {
        set_prop_at(re_ptr, PROP_LAST_INDEX, JsValue::int(0));
    }

    let result = if args.len() > 2 {
        let replacer_val = vm.reg(args[2]);
        if replacer_val.is_object() {
            let o = unsafe { &*replacer_val.as_js_object_ptr() };
            if o.is_function() {
                crate::string::regex_replace_fn(vm, regex, &haystack, replacer_val, is_global)
            } else {
                let replacement = oxide_runtime_api::to_string(replacer_val);
                NativeResult::Ok(vm.new_string(&crate::string::regex_replace_manual(
                    regex,
                    &haystack,
                    &replacement,
                    is_global,
                )))
            }
        } else {
            let replacement = oxide_runtime_api::to_string(replacer_val);
            NativeResult::Ok(vm.new_string(&crate::string::regex_replace_manual(
                regex,
                &haystack,
                &replacement,
                is_global,
            )))
        }
    } else {
        NativeResult::Ok(vm.new_string(&crate::string::regex_replace_manual(regex, &haystack, "", is_global)))
    };

    if is_global {
        let mut last_end = 0;
        for m in regex.find_iter(&haystack) {
            last_end = m.range().end;
        }
        set_prop_at(re_ptr, PROP_LAST_INDEX, JsValue::int(last_end as i32));
    }
    result
}

/// `RegExp.prototype[Symbol.search](string)`：返回首个匹配位置（字符索引），
/// 无匹配返回 -1。global 标志不影响 search。
pub fn regexp_symbol_search<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let (regex, haystack) = match regexp_regex_and_text(vm, args) {
        Ok(pair) => pair,
        Err(err) => return NativeResult::Err(err),
    };
    if let Some(m) = regex.find(&haystack) {
        return NativeResult::Ok(JsValue::int(m.range().start as i32));
    }
    NativeResult::Ok(JsValue::int(-1))
}

/// `RegExp.prototype[Symbol.split](string, limit)`：按匹配切分，捕获组作为
/// 分隔元素插入结果；limit 限制结果长度，缺省切分全部。
pub fn regexp_symbol_split<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let (regex, haystack) = match regexp_regex_and_text(vm, args) {
        Ok(pair) => pair,
        Err(err) => return NativeResult::Err(err),
    };
    let limit = if args.len() > 2 {
        let l = oxide_runtime_api::to_integer_or_infinity(vm.reg(args[2]));
        if l.is_infinite() {
            u32::MAX as usize
        } else {
            (l.max(0.0).trunc() as u64).min(u32::MAX as u64) as usize
        }
    } else {
        u32::MAX as usize
    };

    let mut parts: Vec<String> = Vec::new();
    let mut last_end = 0;
    for m in regex.find_iter(&haystack) {
        if parts.len() >= limit {
            break;
        }
        let range = m.range();
        parts.push(haystack[last_end..range.start].to_string());
        if parts.len() >= limit {
            break;
        }
        for i in 1..=m.captures.len() {
            if parts.len() >= limit {
                break;
            }
            match m.group(i) {
                Some(g) => parts.push(haystack[g.start..g.end].to_string()),
                None => parts.push(String::new()),
            }
        }
        last_end = range.end;
    }
    if last_end <= haystack.len() && parts.len() < limit {
        parts.push(haystack[last_end..].to_string());
    }
    NativeResult::Ok(crate::string::make_string_array(vm, &parts))
}

/// `RegExp.prototype[Symbol.matchAll](string)`：返回按 global 语义逐个产出
/// 匹配数组的迭代器。global 正则直接复用（初始下标取 lastIndex）；
/// 非 global 正则复制一份加 `g` 标志后迭代。
pub fn regexp_symbol_match_all<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
    let re_ptr = match get_regexp_ptr(vm, args) {
        Ok(ptr) => ptr,
        Err(err) => return NativeResult::Err(err),
    };
    let re = unsafe { &*re_ptr };
    let is_global = is_global(re);
    let last_index = vm.coerce_number_bounded(get_prop(re, PROP_LAST_INDEX)).unwrap_or(f64::NAN) as usize;
    let haystack = match regexp_string_arg(vm, args) {
        Ok(s) => s,
        Err(err) => return NativeResult::Err(err),
    };

    // 迭代目标：global 用原正则，非 global 复制并补 g 标志。
    let iter_re = if is_global {
        vm.reg(args[0])
    } else {
        let source = {
            let val = get_prop(re, PROP_SOURCE);
            vm.lookup_str(val).unwrap_or_default()
        };
        let mut flags = {
            let val = get_prop(re, PROP_FLAGS);
            vm.lookup_str(val).unwrap_or_default()
        };
        if !flags.contains('g') {
            flags.push('g');
        }
        let compiled = match regress::Regex::with_flags(&source, flags.as_str()) {
            Ok(rx) => rx,
            Err(e) => {
                return NativeResult::Err(crate::error::create_syntax_error(
                    vm,
                    &format!("Invalid regular expression: {e}"),
                ));
            }
        };
        let object_proto = vm.session().builtin_world().object_proto.as_ptr() as *mut JsObject;
        let mut stub = JsObject::new_empty(EMPTY_SHAPE_ID, JsValue::from_js_object(object_proto));
        let raw = Box::into_raw(Box::new(compiled)) as *const u8;
        stub.set_native_fn(Some(unsafe { NativeFnPtr::from_raw(raw as *const ()) }));
        JsValue::from_js_object(vm.alloc_object(stub))
    };

    // 复用 String.prototype.matchAll 的迭代器包装（next 经 string_match_all_next 推进）。
    let object_proto = vm.session().builtin_world().object_proto.as_ptr() as *mut JsObject;
    let wrapper = vm
        .epoch()
        .alloc(JsObject::new_empty(EMPTY_SHAPE_ID, JsValue::from_js_object(object_proto)));
    let wrapper_obj = unsafe { &mut *wrapper };
    let input_si = vm.kernel_core().perm_interner().intern(crate::string::MALL_INPUT).0;
    let index_si = vm.kernel_core().perm_interner().intern(crate::string::MALL_INDEX).0;
    let re_si = vm.kernel_core().perm_interner().intern(crate::string::MALL_RE).0;
    let next_si = vm.kernel_core().perm_interner().intern("next").0;
    let input_val = vm.new_string(&haystack);
    vm.set_or_create_prop_value(wrapper_obj, input_si, input_val);
    vm.set_or_create_prop_value(wrapper_obj, index_si, JsValue::int(last_index as i32));
    vm.set_or_create_prop_value(wrapper_obj, re_si, iter_re);
    let next_fn =
        crate::string::make_public_native_fn(vm, "next", crate::string::string_match_all_next::<H> as *const (), 0);
    vm.set_or_create_prop_value(wrapper_obj, next_si, next_fn);
    NativeResult::Ok(JsValue::from_js_object(wrapper))
}