/* There's a lot of cases of doubled parens in here like this:

  while ( (he = ...) ) {

This shuts up warnings from gcc -Wall
*/

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#define NEED_newRV_noinc
#define NEED_sv_2pv_flags
#define NEED_sv_2pv_nolen
#include "ppport.h"

#define DECLARE_KEY(name) SV *key_##name; U32 hash_##name;

#define PREHASH_KEY_WITH_VALUE(name, value) do { \
    key_##name = newSVpvs(value); \
    PERL_HASH(hash_##name, value, sizeof(value) - 1); \
} while (0)

/* this is basically the same as the above macro, except that the value will be
 * the stringified name. However, we can't just implement this in terms of
 * PREHASH_KEY_WITH_VALUE as that'd cause macro expansion on the value of
 * 'name' when it's being passed to the other macro. suggestions on how to make
 * this more elegant would be much appreciated */

#define PREHASH_KEY(name) do { \
    key_##name = newSVpvs(#name); \
    PERL_HASH(hash_##name, #name, sizeof(#name) - 1); \
} while (0)

DECLARE_KEY(name);
DECLARE_KEY(package);
DECLARE_KEY(package_name);
DECLARE_KEY(body);
DECLARE_KEY(package_cache_flag);
DECLARE_KEY(methods);
DECLARE_KEY(VERSION);
DECLARE_KEY(ISA);

SV *method_metaclass;
SV *associated_metaclass;
SV *wrap;


#define check_package_cache_flag(stash) mop_check_package_cache_flag(aTHX_ stash)
#if PERL_VERSION >= 10

static UV
mop_check_package_cache_flag(pTHX_ HV* stash) {
    assert(SvTYPE(stash) == SVt_PVHV);

    /* here we're trying to implement a c version of mro::get_pkg_gen($stash),
     * however the perl core doesn't make it easy for us. It doesn't provide an
     * api that just does what we want.
     *
     * However, we know that the information we want is, inside the core,
     * available using HvMROMETA(stash)->pkg_gen. Unfortunately, although the
     * HvMROMETA macro is public, it is implemented using Perl_mro_meta_init,
     * which is not public and only available inside the core, as the mro
     * interface as well as the structure returned by mro_meta_init isn't
     * considered to be stable yet.
     *
     * Perl_mro_meta_init isn't declared static, so we could just define it
     * ourselfs if perls headers don't do that for us, except that won't work
     * on platforms where symbols need to be explicitly exported when linking
     * shared libraries.
     *
     * So our, hopefully temporary, solution is to be even more evil and
     * basically reimplement HvMROMETA in a very fragile way that'll blow up
     * when the relevant parts of the mro implementation in core change.
     *
     * :-(
     *
     */

    return HvAUX(stash)->xhv_mro_meta
         ? HvAUX(stash)->xhv_mro_meta->pkg_gen
         : 0;
}

#else /* pre 5.10.0 */

static UV
mop_check_package_cache_flag(pTHX_ HV *stash) {
    PERL_UNUSED_ARG(stash);
    assert(SvTYPE(stash) == SVt_PVHV);

    return PL_sub_generation;
}
#endif

#define call0(s, m)  mop_call0(aTHX_ s, m)
static SV *
mop_call0(pTHX_ SV *const self, SV *const method) {
    dSP;
    SV *ret;

    PUSHMARK(SP);
    XPUSHs(self);
    PUTBACK;

    call_sv(method, G_SCALAR | G_METHOD);

    SPAGAIN;
    ret = POPs;
    PUTBACK;

    return ret;
}

static int
get_code_info (SV *coderef, char **pkg, char **name)
{
    if (!SvOK(coderef) || !SvROK(coderef) || SvTYPE(SvRV(coderef)) != SVt_PVCV) {
        return 0;
    }

    coderef = SvRV(coderef);
    /* I think this only gets triggered with a mangled coderef, but if
       we hit it without the guard, we segfault. The slightly odd return
       value strikes me as an improvement (mst)
    */
#ifdef isGV_with_GP
    if ( isGV_with_GP(CvGV(coderef)) ) {
#endif
        *pkg     = HvNAME( GvSTASH(CvGV(coderef)) );
        *name    = GvNAME( CvGV(coderef) );
#ifdef isGV_with_GP
    } else {
        *pkg     = "__UNKNOWN__";
        *name    = "__ANON__";
    }
#endif

    return 1;
}

typedef enum {
    TYPE_FILTER_NONE,
    TYPE_FILTER_CODE,
    TYPE_FILTER_ARRAY,
    TYPE_FILTER_IO,
    TYPE_FILTER_HASH,
    TYPE_FILTER_SCALAR,
} type_filter_t;

static HV *
get_all_package_symbols(HV *stash, type_filter_t filter)
{
    HE *he;
    HV *ret = newHV();

    (void)hv_iterinit(stash);

    if (filter == TYPE_FILTER_NONE) {
        while ( (he = hv_iternext(stash)) ) {
            STRLEN keylen;
            char *key = HePV(he, keylen);
            if (!hv_store(ret, key, keylen, SvREFCNT_inc(HeVAL(he)), 0)) {
                croak("failed to store glob ref");
            }
        }

        return ret;
    }

    while ( (he = hv_iternext(stash)) ) {
        SV *const gv = HeVAL(he);
        SV *sv = NULL;
        char *key;
        STRLEN keylen;
        char *package;
        SV *fq;

        switch( SvTYPE(gv) ) {
#ifndef SVt_RV
            case SVt_RV:
#endif
            case SVt_PV:
            case SVt_IV:
                /* expand the gv into a real typeglob if it
                 * contains stub functions and we were asked to
                 * return CODE symbols */
                if (filter == TYPE_FILTER_CODE) {
                    if (SvROK(gv)) {
                        /* we don't really care about the length,
                           but that's the API */
                        key = HePV(he, keylen);
                        package = HvNAME(stash);
                        fq = newSVpvf("%s::%s", package, key);
                        sv = (SV *)get_cv(SvPV_nolen(fq), 0);
                        break;
                    }

                    key = HePV(he, keylen);
                    gv_init((GV *)gv, stash, key, keylen, GV_ADDMULTI);
                }
                /* fall through */
            case SVt_PVGV:
                switch (filter) {
                    case TYPE_FILTER_CODE:   sv = (SV *)GvCVu(gv); break;
                    case TYPE_FILTER_ARRAY:  sv = (SV *)GvAV(gv);  break;
                    case TYPE_FILTER_IO:     sv = (SV *)GvIO(gv);  break;
                    case TYPE_FILTER_HASH:   sv = (SV *)GvHV(gv);  break;
                    case TYPE_FILTER_SCALAR: sv = (SV *)GvSV(gv);  break;
                    default:
                        croak("Unknown type");
                }
                break;
            default:
                continue;
        }

        if (sv) {
            char *key = HePV(he, keylen);
            if (!hv_store(ret, key, keylen, newRV_inc(sv), 0)) {
                croak("failed to store symbol ref");
            }
        }
    }

    return ret;
}


static void
mop_update_method_map(pTHX_ SV *const self, SV *const class_name, HV *const stash, HV *const map) {
    const char *const class_name_pv = HvNAME(stash); /* must be HvNAME(stash), not SvPV_nolen_const(class_name) */
    SV   *method_metaclass_name;
    char *method_name;
    I32   method_name_len;
    SV   *coderef;
    HV   *symbols;
    dSP;

    symbols = get_all_package_symbols(stash, TYPE_FILTER_CODE);

    (void)hv_iterinit(symbols);
    while ( (coderef = hv_iternextsv(symbols, &method_name, &method_name_len)) ) {
        CV *cv = (CV *)SvRV(coderef);
        char *cvpkg_name;
        char *cv_name;
        SV *method_slot;
        SV *method_object;

        if (!get_code_info(coderef, &cvpkg_name, &cv_name)) {
            continue;
        }

        /* this checks to see that the subroutine is actually from our package  */
        if ( !(strEQ(cvpkg_name, "constant") && strEQ(cv_name, "__ANON__")) ) {
            if ( strNE(cvpkg_name, class_name_pv) ) {
                continue;
            }
        }

        method_slot = *hv_fetch(map, method_name, method_name_len, TRUE);
        if ( SvOK(method_slot) ) {
            SV *const body = call0(method_slot, key_body); /* $method_object->body() */
            if ( SvROK(body) && ((CV *) SvRV(body)) == cv ) {
                continue;
            }
        }

        method_metaclass_name = call0(self, method_metaclass); /* $self->method_metaclass() */

        /*
            $method_object = $method_metaclass->wrap(
                $cv,
                associated_metaclass => $self,
                package_name         => $class_name,
                name                 => $method_name
            );
        */
        ENTER;
        SAVETMPS;

        PUSHMARK(SP);
        EXTEND(SP, 8);
        PUSHs(method_metaclass_name); /* invocant */
        mPUSHs(newRV_inc((SV *)cv));
        PUSHs(associated_metaclass);
        PUSHs(self);
        PUSHs(key_package_name);
        PUSHs(class_name);
        PUSHs(key_name);
        mPUSHs(newSVpv(method_name, method_name_len));
        PUTBACK;

        call_sv(wrap, G_SCALAR | G_METHOD);
        SPAGAIN;
        method_object = POPs;
        PUTBACK;
        /* $map->{$method_name} = $method_object */
        sv_setsv(method_slot, method_object);

        FREETMPS;
        LEAVE;
    }
}

/*
get_code_info:
  Pass in a coderef, returns:
  [ $pkg_name, $coderef_name ] ie:
  [ 'Foo::Bar', 'new' ]
*/

MODULE = Class::MOP   PACKAGE = Class::MOP

BOOT:
    PREHASH_KEY(name);
    PREHASH_KEY(body);
    PREHASH_KEY(package);
    PREHASH_KEY(package_name);
    PREHASH_KEY(methods);
    PREHASH_KEY(ISA);
    PREHASH_KEY(VERSION);
    PREHASH_KEY_WITH_VALUE(package_cache_flag, "_package_cache_flag");

    method_metaclass     = newSVpvs("method_metaclass");
    wrap                 = newSVpvs("wrap");
    associated_metaclass = newSVpvs("associated_metaclass");


PROTOTYPES: DISABLE

# use prototype here to be compatible with get_code_info from Sub::Identify
void
get_code_info(coderef)
    SV *coderef
    PROTOTYPE: $
    PREINIT:
        char *pkg  = NULL;
        char *name = NULL;
    PPCODE:
        if (get_code_info(coderef, &pkg, &name)) {
            EXTEND(SP, 2);
            PUSHs(newSVpv(pkg, 0));
            PUSHs(newSVpv(name, 0));
        }

# This is some pretty grotty logic. It _should_ be parallel to the
# pure Perl version in lib/Class/MOP.pm, so if you want to understand
# it we suggest you start there.
void
is_class_loaded(klass=&PL_sv_undef)
    SV *klass
    PREINIT:
        HV *stash;
        char *key;
        I32 keylen;
        SV *gv;
    PPCODE:
        if (!SvPOK(klass) || !SvCUR(klass)) {
            XSRETURN_NO;
        }

        stash = gv_stashsv(klass, 0);
        if (!stash) {
            XSRETURN_NO;
        }

        if (hv_exists_ent (stash, key_VERSION, hash_VERSION)) {
            HE *version = hv_fetch_ent(stash, key_VERSION, 0, hash_VERSION);
            SV *version_sv;
            if (version && HeVAL(version) && (version_sv = GvSV(HeVAL(version)))) {
                if (SvROK(version_sv)) {
                    SV *version_sv_ref = SvRV(version_sv);

                    if (SvOK(version_sv_ref)) {
                        XSRETURN_YES;
                    }
                }
                else if (SvOK(version_sv)) {
                    XSRETURN_YES;
                }
            }
        }

        if (hv_exists_ent (stash, key_ISA, hash_ISA)) {
            HE *isa = hv_fetch_ent(stash, key_ISA, 0, hash_ISA);
            if (isa && HeVAL(isa) && GvAV(HeVAL(isa))) {
                XSRETURN_YES;
            }
        }

        (void)hv_iterinit(stash);
        while ((gv = hv_iternextsv(stash, &key, &keylen))) {
            if (keylen <= 0) {
                continue;
            }

            if (key[keylen - 1] == ':' && key[keylen - 2] == ':') {
                continue;
            }

            if (!isGV(gv) || GvCV(gv)) {
                XSRETURN_YES;
            }
        }

        XSRETURN_NO;

MODULE = Class::MOP   PACKAGE = Class::MOP::Package

void
get_all_package_symbols(self, filter=TYPE_FILTER_NONE)
    SV *self
    type_filter_t filter
    PREINIT:
        HV *stash = NULL;
        HV *symbols = NULL;
        register HE *he;
    PPCODE:
        if ( ! SvROK(self) ) {
            die("Cannot call get_all_package_symbols as a class method");
        }

        if (GIMME_V == G_VOID) {
            XSRETURN_EMPTY;
        }

        PUTBACK;

        if ( (he = hv_fetch_ent((HV *)SvRV(self), key_package, 0, hash_package)) ) {
            stash = gv_stashsv(HeVAL(he), 0);
        }


        if (!stash) {
            XSRETURN_UNDEF;
        }

        symbols = get_all_package_symbols(stash, filter);
        PUSHs(sv_2mortal(newRV_noinc((SV *)symbols)));

void
name(self)
    SV *self
    PREINIT:
        register HE *he;
    PPCODE:
        if ( ! SvROK(self) ) {
            die("Cannot call name as a class method");
        }

        if ( (he = hv_fetch_ent((HV *)SvRV(self), key_package, 0, hash_package)) )
            XPUSHs(HeVAL(he));
        else
            ST(0) = &PL_sv_undef;

MODULE = Class::MOP   PACKAGE = Class::MOP::Attribute

void
name(self)
    SV *self
    PREINIT:
        register HE *he;
    PPCODE:
        if ( ! SvROK(self) ) {
            die("Cannot call name as a class method");
        }

        if ( (he = hv_fetch_ent((HV *)SvRV(self), key_name, 0, hash_name)) )
            XPUSHs(HeVAL(he));
        else
            ST(0) = &PL_sv_undef;

MODULE = Class::MOP   PACKAGE = Class::MOP::Method

void
name(self)
    SV *self
    PREINIT:
        register HE *he;
    PPCODE:
        if ( ! SvROK(self) ) {
            die("Cannot call name as a class method");
        }

        if ( (he = hv_fetch_ent((HV *)SvRV(self), key_name, 0, hash_name)) )
            XPUSHs(HeVAL(he));
        else
            ST(0) = &PL_sv_undef;

void
package_name(self)
    SV *self
    PREINIT:
        register HE *he;
    PPCODE:
        if ( ! SvROK(self) ) {
            die("Cannot call package_name as a class method");
        }

        if ( (he = hv_fetch_ent((HV *)SvRV(self), key_package_name, 0, hash_package_name)) )
            XPUSHs(HeVAL(he));
        else
            ST(0) = &PL_sv_undef;

void
body(self)
    SV *self
    PREINIT:
        register HE *he;
    PPCODE:
        if ( ! SvROK(self) ) {
            die("Cannot call body as a class method");
        }

        if ( (he = hv_fetch_ent((HV *)SvRV(self), key_body, 0, hash_body)) )
            XPUSHs(HeVAL(he));
        else
            ST(0) = &PL_sv_undef;


MODULE = Class::MOP    PACKAGE = Class::MOP::Class

void
get_method_map(self)
    SV *self
    PREINIT:
        HV *const obj        = (HV *)SvRV(self);
        SV *const class_name = HeVAL( hv_fetch_ent(obj, key_package, 0, hash_package) );
        HV *const stash      = gv_stashsv(class_name, 0);
        UV  const current    = check_package_cache_flag(stash);
        SV *const cache_flag = HeVAL( hv_fetch_ent(obj, key_package_cache_flag, TRUE, hash_package_cache_flag));
        SV *const map_ref    = HeVAL( hv_fetch_ent(obj, key_methods, TRUE, hash_methods));
    PPCODE:
        /* in  $self->{methods} does not yet exist (or got deleted) */
        if ( !SvROK(map_ref) || SvTYPE(SvRV(map_ref)) != SVt_PVHV ) {
            SV *new_map_ref = newRV_noinc((SV *)newHV());
            sv_2mortal(new_map_ref);
            sv_setsv(map_ref, new_map_ref);
        }

        if ( !SvOK(cache_flag) || SvUV(cache_flag) != current ) {
            mop_update_method_map(aTHX_ self, class_name, stash, (HV *)SvRV(map_ref));
            sv_setuv(cache_flag, check_package_cache_flag(stash)); /* update_cache_flag() */
        }

        XPUSHs(map_ref);