#include <memory>
#include <cstdio>
#include <cmath>

#include "cs_bcode.hh"
#include "cs_state.hh"
#include "cs_thread.hh"
#include "cs_strman.hh"
#include "cs_vm.hh"
#include "cs_parser.hh"
#include "cs_error.hh"

namespace cubescript {

internal_state::internal_state(alloc_func af, void *data):
    allocf{af}, aptr{data},
    idents{allocator_type{this}},
    identmap{allocator_type{this}},
    strman{create<string_pool>(this)},
    empty{bcode_init_empty(this)}
{}

internal_state::~internal_state() {
    for (auto &p: idents) {
        destroy(&ident_p{*p.second}.impl());
    }
    bcode_free_empty(this, empty);
    destroy(strman);
}

void *internal_state::alloc(void *ptr, size_t os, size_t ns) {
    void *p = allocf(aptr, ptr, os, ns);
    if (!p && ns) {
        throw std::bad_alloc{};
    }
    return p;
}

static void *default_alloc(void *, void *p, size_t, size_t ns) {
    if (!ns) {
        std::free(p);
        return nullptr;
    }
    return std::realloc(p, ns);
}

ident *internal_state::add_ident(ident *id, ident_impl *impl) {
    if (!id) {
        return nullptr;
    }
    ident_p{*id}.impl(impl);
    idents[id->name()] = id;
    impl->p_index = int(identmap.size());
    identmap.push_back(id);
    return identmap.back();
}

ident &internal_state::new_ident(state &cs, std::string_view name, int flags) {
    ident *id = get_ident(name);
    if (!id) {
        if (!is_valid_name(name)) {
            throw error_p::make(
                cs, "'%s' is not a valid identifier name", name.data()
            );
        }
        auto *inst = create<alias_impl>(
            cs, string_ref{cs, name}, flags
        );
        id = add_ident(inst, inst);
    }
    return *id;
}

ident *internal_state::get_ident(std::string_view name) const {
    auto id = idents.find(name);
    if (id == idents.end()) {
        return nullptr;
    }
    return id->second;
}

/* public interfaces */

state::state(): state{default_alloc, nullptr} {}

state::state(alloc_func func, void *data) {
    command *p;

    if (!func) {
        func = default_alloc;
    }
    /* allocator is not set up yet, use func directly */
    auto *statep = static_cast<internal_state *>(
        func(data, nullptr, 0, sizeof(internal_state))
    );
    /* allocator will be set up in the constructor */
    new (statep) internal_state{func, data};

    try {
        p_tstate = statep->create<thread_state>(statep);
    } catch (...) {
        statep->destroy(statep);
        throw;
    }

    p_tstate->pstate = this;
    p_tstate->istate = statep;
    p_tstate->owner = true;

    for (std::size_t i = 0; i < MAX_ARGUMENTS; ++i) {
        char buf[16];
        snprintf(buf, sizeof(buf), "arg%zu", i + 1);
        statep->new_ident(
            *this, static_cast<char const *>(buf), IDENT_FLAG_ARG
        );
    }

    statep->id_dummy = &statep->new_ident(*this, "//dummy", IDENT_FLAG_UNKNOWN);

    statep->ivar_numargs  = &new_var("numargs", 0, true);
    statep->ivar_dbgalias = &new_var("dbgalias", 4);

    /* default handlers for variables */

    statep->cmd_ivar = &new_command("//ivar_builtin", "$i#", [](
        auto &cs, auto args, auto &
    ) {
        auto &iv = static_cast<builtin_var &>(args[0].get_ident(cs));
        if (args[2].get_integer() <= 1) {
            std::printf("%s = ", iv.name().data());
            std::printf(INTEGER_FORMAT, iv.value().get_integer());
            std::printf("\n");
        } else {
            iv.set_value(cs, args[1]);
        }
    });

    statep->cmd_fvar = &new_command("//fvar_builtin", "$f#", [](
        auto &cs, auto args, auto &
    ) {
        auto &fv = static_cast<builtin_var &>(args[0].get_ident(cs));
        if (args[2].get_integer() <= 1) {
            auto val = fv.value().get_float();
            std::printf("%s = ", fv.name().data());
            if (std::floor(val) == val) {
                std::printf(ROUND_FLOAT_FORMAT, val);
            } else {
                std::printf(FLOAT_FORMAT, val);
            }
            std::printf("\n");
        } else {
            fv.set_value(cs, args[1]);
        }
    });

    statep->cmd_svar = &new_command("//svar_builtin", "$s#", [](
        auto &cs, auto args, auto &
    ) {
        auto &sv = static_cast<builtin_var &>(args[0].get_ident(cs));
        if (args[2].get_integer() <= 1) {
            auto val = sv.value().get_string(cs);
            if (val.view().find('"') == std::string_view::npos) {
                std::printf("%s = \"%s\"\n", sv.name().data(), val.data());
            } else {
                std::printf("%s = [%s]\n", sv.name().data(), val.data());
            }
        } else {
            sv.set_value(cs, args[1]);
        }
    });

    statep->cmd_var_changed = nullptr;

    /* builtins */

    p = &new_command("do", "b", [](auto &cs, auto args, auto &res) {
        res = args[0].get_code().call(cs);
    });
    static_cast<command_impl *>(p)->p_type = ID_DO;

    p = &new_command("doargs", "b", [](auto &cs, auto args, auto &res) {
        res = exec_code_with_args(*cs.p_tstate, args[0].get_code());
    });
    static_cast<command_impl *>(p)->p_type = ID_DOARGS;

    p = &new_command("if", "abb", [](auto &cs, auto args, auto &res) {
        res = (args[0].get_bool() ? args[1] : args[2]).get_code().call(cs);
    });
    static_cast<command_impl *>(p)->p_type = ID_IF;

    p = &new_command("result", "a", [](auto &, auto args, auto &res) {
        res = std::move(args[0]);
    });
    static_cast<command_impl *>(p)->p_type = ID_RESULT;

    p = &new_command("!", "a", [](auto &, auto args, auto &res) {
        res.set_integer(!args[0].get_bool());
    });
    static_cast<command_impl *>(p)->p_type = ID_NOT;

    p = &new_command("&&", "c1...", [](auto &cs, auto args, auto &res) {
        if (args.empty()) {
            res.set_integer(1);
        } else {
            for (size_t i = 0; i < args.size(); ++i) {
                auto code = args[i].get_code();
                if (code) {
                    res = code.call(cs);
                } else {
                    res = std::move(args[i]);
                }
                if (!res.get_bool()) {
                    break;
                }
            }
        }
    });
    static_cast<command_impl *>(p)->p_type = ID_AND;

    p = &new_command("||", "c1...", [](auto &cs, auto args, auto &res) {
        if (args.empty()) {
            res.set_integer(0);
        } else {
            for (size_t i = 0; i < args.size(); ++i) {
                auto code = args[i].get_code();
                if (code) {
                    res = code.call(cs);
                } else {
                    res = std::move(args[i]);
                }
                if (res.get_bool()) {
                    break;
                }
            }
        }
    });
    static_cast<command_impl *>(p)->p_type = ID_OR;

    p = &new_command("local", "", nullptr);
    static_cast<command_impl *>(p)->p_type = ID_LOCAL;

    p = &new_command("break", "", [](auto &cs, auto, auto &) {
        if (cs.p_tstate->loop_level) {
            throw break_exception{};
        } else {
            throw error{cs, "no loop to break"};
        }
    });
    static_cast<command_impl *>(p)->p_type = ID_BREAK;

    p = &new_command("continue", "", [](auto &cs, auto, auto &) {
        if (cs.p_tstate->loop_level) {
            throw continue_exception{};
        } else {
            throw error{cs, "no loop to continue"};
        }
    });
    static_cast<command_impl *>(p)->p_type = ID_CONTINUE;
}

LIBCUBESCRIPT_EXPORT state::~state() {
    if (!p_tstate || !p_tstate->owner) {
        return;
    }
    auto *sp = p_tstate->istate;
    sp->destroy(p_tstate);
    sp->destroy(sp);
}

LIBCUBESCRIPT_EXPORT state::state(state &&s) {
    swap(s);
}

LIBCUBESCRIPT_EXPORT state &state::operator=(state &&s) {
    if (p_tstate && p_tstate->owner) {
        auto *sp = p_tstate->istate;
        sp->destroy(p_tstate);
        sp->destroy(sp);
    }
    p_tstate = s.p_tstate;
    s.p_tstate = nullptr;
    return *this;
}

LIBCUBESCRIPT_EXPORT void state::swap(state &s) {
    std::swap(p_tstate, s.p_tstate);
}

state::state(void *is) {
    auto *s = static_cast<internal_state *>(is);
    p_tstate = s->create<thread_state>(s);
    p_tstate->pstate = this;
    p_tstate->istate = s;
    p_tstate->owner = false;
}

LIBCUBESCRIPT_EXPORT state state::new_thread() {
    return state{p_tstate->istate};
}

LIBCUBESCRIPT_EXPORT hook_func state::call_hook(hook_func func) {
    return p_tstate->set_hook(std::move(func));
}

LIBCUBESCRIPT_EXPORT hook_func const &state::call_hook() const {
    return p_tstate->get_hook();
}

LIBCUBESCRIPT_EXPORT hook_func &state::call_hook() {
    return p_tstate->get_hook();
}

LIBCUBESCRIPT_EXPORT void *state::alloc(void *ptr, size_t os, size_t ns) {
    return p_tstate->istate->alloc(ptr, os, ns);
}

LIBCUBESCRIPT_EXPORT std::size_t state::ident_count() const {
    return p_tstate->istate->identmap.size();
}

LIBCUBESCRIPT_EXPORT std::optional<
    std::reference_wrapper<ident>
> state::get_ident(std::string_view name) {
    auto *id = p_tstate->istate->get_ident(name);
    if (!id) {
        return std::nullopt;
    }
    return *id;
}

LIBCUBESCRIPT_EXPORT std::optional<
    std::reference_wrapper<ident const>
> state::get_ident(std::string_view name) const {
    auto *id = p_tstate->istate->get_ident(name);
    if (!id) {
        return std::nullopt;
    }
    return *id;
}

LIBCUBESCRIPT_EXPORT ident &state::get_ident(std::size_t index) {
    return *p_tstate->istate->identmap[index];
}

LIBCUBESCRIPT_EXPORT ident const &state::get_ident(std::size_t index) const {
    return *p_tstate->istate->identmap[index];
}

LIBCUBESCRIPT_EXPORT void state::clear_override(ident &id) {
    if (!id.is_overridden(*this)) {
        return;
    }
    switch (id.type()) {
        case ident_type::ALIAS: {
            auto &ast = p_tstate->get_astack(static_cast<alias *>(&id));
            ast.node->val_s.set_string("", *this);
            ast.node->code = bcode_ref{};
            ast.flags &= ~IDENT_FLAG_OVERRIDDEN;
            return;
        }
        case ident_type::VAR: {
            auto &v = static_cast<var_impl &>(id);
            any_value oldv = v.value();
            v.p_storage = std::move(v.p_override);
            var_changed(*p_tstate, v, oldv);
            static_cast<var_impl *>(
                static_cast<builtin_var *>(&v)
            )->p_flags &= ~IDENT_FLAG_OVERRIDDEN;
            return;
        }
        default:
            break;
    }
}

LIBCUBESCRIPT_EXPORT void state::clear_overrides() {
    for (auto &p: p_tstate->istate->idents) {
        clear_override(*(p.second));
    }
}

inline int var_flags(bool read_only, var_type vtp) {
    int ret = 0;
    if (read_only) {
        ret |= IDENT_FLAG_READONLY;
    }
    switch (vtp) {
        case var_type::PERSISTENT:
            ret |= IDENT_FLAG_PERSIST;
            break;
        case var_type::OVERRIDABLE:
            ret |= IDENT_FLAG_OVERRIDE;
            break;
        default:
            break;
    }
    return ret;
}

static void var_name_check(
    state &cs, ident *id, std::string_view n
) {
    if (id) {
        throw error_p::make(
            cs, "redefinition of ident '%.*s'", int(n.size()), n.data()
        );
    } else if (!is_valid_name(n)) {
        throw error_p::make(
            cs, "'%.*s' is not a valid variable name",
            int(n.size()), n.data()
        );
    }
}

LIBCUBESCRIPT_EXPORT builtin_var &state::new_var(
    std::string_view n, integer_type v, bool read_only, var_type vtp
) {
    auto *iv = p_tstate->istate->create<var_impl>(
        string_ref{*this, n},var_flags(read_only, vtp)
    );
    iv->p_storage.set_integer(v);
    try {
        var_name_check(*this, p_tstate->istate->get_ident(n), n);
    } catch (...) {
        p_tstate->istate->destroy(iv);
        throw;
    }
    p_tstate->istate->add_ident(iv, iv);
    return *iv;
}

LIBCUBESCRIPT_EXPORT builtin_var &state::new_var(
    std::string_view n, float_type v, bool read_only, var_type vtp
) {
    auto *fv = p_tstate->istate->create<var_impl>(
        string_ref{*this, n}, var_flags(read_only, vtp)
    );
    fv->p_storage.set_float(v);
    try {
        var_name_check(*this, p_tstate->istate->get_ident(n), n);
    } catch (...) {
        p_tstate->istate->destroy(fv);
        throw;
    }
    p_tstate->istate->add_ident(fv, fv);
    return *fv;
}

LIBCUBESCRIPT_EXPORT builtin_var &state::new_var(
    std::string_view n, std::string_view v, bool read_only, var_type vtp
) {
    auto *sv = p_tstate->istate->create<var_impl>(
        string_ref{*this, n}, var_flags(read_only, vtp)
    );
    sv->p_storage.set_string(v, *this);
    try {
        var_name_check(*this, p_tstate->istate->get_ident(n), n);
    } catch (...) {
        p_tstate->istate->destroy(sv);
        throw;
    }
    p_tstate->istate->add_ident(sv, sv);
    return *sv;
}

LIBCUBESCRIPT_EXPORT ident &state::new_ident(std::string_view n) {
    return p_tstate->istate->new_ident(*this, n, IDENT_FLAG_UNKNOWN);
}

LIBCUBESCRIPT_EXPORT void state::assign_value(
    std::string_view name, any_value v
) {
    auto id = get_ident(name);
    if (id) {
        switch (id->get().type()) {
            case ident_type::ALIAS: {
                static_cast<alias &>(id->get()).set_value(*this, std::move(v));
                return;
            }
            case ident_type::VAR:
                id->get().call(span_type<any_value>{&v, 1}, *this);
                break;
            default:
                throw error_p::make(
                    *this, "cannot redefine builtin %s with an alias",
                    id->get().name().data()
                );
        }
    } else if (!is_valid_name(name)) {
        throw error_p::make(
            *this, "cannot alias invalid name '%s'", name.data()
        );
    } else {
        auto *a = p_tstate->istate->create<alias_impl>(
            *this, string_ref{*this, name}, std::move(v),
            p_tstate->ident_flags
        );
        p_tstate->istate->add_ident(a, a);
    }
}

LIBCUBESCRIPT_EXPORT any_value state::lookup_value(std::string_view name) {
    ident *id = nullptr;
    auto idopt = get_ident(name);
    if (!idopt) {
        id = nullptr;
    } else {
        id = &idopt->get();
    }
    alias_stack *ast;
    if (id) {
        switch(id->type()) {
            case ident_type::ALIAS: {
                auto *a = static_cast<alias_impl *>(id);
                ast = &p_tstate->get_astack(static_cast<alias *>(id));
                if (ast->flags & IDENT_FLAG_UNKNOWN) {
                    break;
                }
                if (a->is_arg() && !ident_is_used_arg(id, *p_tstate)) {
                    return any_value{};
                }
                return ast->node->val_s.get_plain();
            }
            case ident_type::VAR:
                return static_cast<builtin_var *>(id)->value();
            case ident_type::COMMAND: {
                any_value val{};
                auto *cimpl = static_cast<command_impl *>(id);
                auto &args = p_tstate->vmstack;
                auto osz = args.size();
                /* pad with as many empty values as we need */
                args.resize(osz + cimpl->arg_count());
                try {
                    exec_command(
                        *p_tstate, cimpl, cimpl, &args[osz], val, 0, true
                    );
                } catch (...) {
                    args.resize(osz);
                    throw;
                }
                args.resize(osz);
                return val;
            }
            default:
                return any_value{};
        }
    }
    throw error_p::make(*this, "unknown alias lookup: %s", name.data());
}

LIBCUBESCRIPT_EXPORT void state::reset_value(std::string_view name) {
    auto id = get_ident(name);
    if (!id) {
        throw error_p::make(
            *this, "variable '%s' does not exist", name.data()
        );
    }
    if (id->get().type() == ident_type::VAR) {
        if (static_cast<builtin_var &>(id->get()).is_read_only()) {
            throw error_p::make(
                *this, "variable '%s' is read only", name.data()
            );
        }
    }
    clear_override(id->get());
}

LIBCUBESCRIPT_EXPORT void state::touch_value(std::string_view name) {
    auto id = get_ident(name);
    if (!id) {
        return;
    }
    auto &idr = id->get();
    if (idr.type() != ident_type::VAR) {
        return;
    }
    auto &v = static_cast<builtin_var &>(idr);
    auto vv = v.value();
    var_changed(*p_tstate, v, vv);
}

static char const *allowed_builtins[] = {
    "//ivar", "//fvar", "//svar", "//var_changed",
    "//ivar_builtin", "//fvar_builtin", "//svar_builtin",
    nullptr
};

LIBCUBESCRIPT_EXPORT command &state::new_command(
    std::string_view name, std::string_view args, command_func func
) {
    int nargs = 0;
    for (auto fmt = args.begin(); fmt != args.end(); ++fmt) {
        switch (*fmt) {
            case 'i':
            case 'f':
            case 'a':
            case 'c':
            case '#':
            case 's':
            case 'b':
            case 'v':
            case '$':
                ++nargs;
                break;
            case '1':
            case '2':
            case '3':
            case '4': {
                int nrep = (*fmt - '0');
                if (nargs < nrep) {
                    throw error{
                        *this, "not enough arguments to repeat"
                    };
                }
                if ((args.end() - fmt) != 4) {
                    throw error{
                        *this, "malformed argument list"
                    };
                }
                if (fmt[1] != '.') {
                    throw error{
                        *this, "repetition without variadic arguments"
                    };
                }
                nargs -= nrep;
                break;
            }
            case '.':
                if (
                    ((fmt + 3) != args.end()) ||
                    std::memcmp(&fmt[0], "...", 3)
                ) {
                    throw error{
                        *this, "unterminated variadic argument list"
                    };
                }
                fmt += 2;
                break;
            default:
                throw error_p::make(
                    *this, "invalid argument type: %c", *fmt
                );
        }
    }
    auto &is = *p_tstate->istate;
    auto *cmd = is.create<command_impl>(
        string_ref{*this, name}, string_ref{*this, args},
        nargs, std::move(func)
    );
    /* we can set these builtins */
    command **bptrs[] = {
        &is.cmd_ivar, &is.cmd_fvar, &is.cmd_svar, &is.cmd_var_changed
    };
    auto nbptrs = sizeof(bptrs) / sizeof(*bptrs);
    /* provided a builtin */
    if ((name.size() >= 2) && (name[0] == '/') && (name[1] == '/')) {
        /* sanitize */
        for (auto **p = allowed_builtins; *p; ++p) {
            if (!name.compare(*p)) {
                /* if it's one of the settable ones, maybe set it */
                if (std::size_t(p - allowed_builtins) < nbptrs) {
                    if (!is.get_ident(name)) {
                        /* only set if it does not exist already */
                        *bptrs[p - allowed_builtins] = cmd;
                        goto do_add;
                    }
                }
                /* this will ensure we're not redefining them */
                goto valid;
            }
        }
        /* we haven't found one matching the list, so error */
        is.destroy(cmd);
        throw error_p::make(
            *this, "forbidden builtin command: %.*s",
            int(name.size()), name.data()
        );
    }
valid:
    if (is.get_ident(name)) {
        is.destroy(cmd);
        throw error_p::make(
            *this, "redefinition of ident '%.*s'",
            int(name.size()), name.data()
        );
    }
do_add:
    is.add_ident(cmd, cmd);
    return *cmd;
}

LIBCUBESCRIPT_EXPORT bcode_ref state::compile(
    std::string_view v, std::string_view source
) {
    gen_state gs{*p_tstate};
    gs.gen_main(v, source);
    return gs.steal_ref();
}

LIBCUBESCRIPT_EXPORT bool state::override_mode() const {
    return (p_tstate->ident_flags & IDENT_FLAG_OVERRIDDEN);
}

LIBCUBESCRIPT_EXPORT bool state::override_mode(bool v) {
    bool was = override_mode();
    if (v) {
        p_tstate->ident_flags |= IDENT_FLAG_OVERRIDDEN;
    } else {
        p_tstate->ident_flags &= ~IDENT_FLAG_OVERRIDDEN;
    }
    return was;
}

LIBCUBESCRIPT_EXPORT bool state::persist_mode() const {
    return (p_tstate->ident_flags & IDENT_FLAG_PERSIST);
}

LIBCUBESCRIPT_EXPORT bool state::persist_mode(bool v) {
    bool was = persist_mode();
    if (v) {
        p_tstate->ident_flags |= IDENT_FLAG_PERSIST;
    } else {
        p_tstate->ident_flags &= ~IDENT_FLAG_PERSIST;
    }
    return was;
}

LIBCUBESCRIPT_EXPORT std::size_t state::max_call_depth() const {
    return p_tstate->max_call_depth;
}

LIBCUBESCRIPT_EXPORT std::size_t state::max_call_depth(std::size_t v) {
    auto old = p_tstate->max_call_depth;
    p_tstate->max_call_depth = v;
    return old;
}

LIBCUBESCRIPT_EXPORT void std_init_all(state &cs) {
    std_init_base(cs);
    std_init_math(cs);
    std_init_string(cs);
    std_init_list(cs);
}

} /* namespace cubescript */