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/************************************************

enumerator.c - provides Enumerator class

$Author: knu $

Copyright (C) 2001-2003 Akinori MUSHA

$Idaemons: /home/cvs/rb/enumerator/enumerator.c,v 1.1.1.1 2001/07/15 10:12:48 knu Exp $
$RoughId: enumerator.c,v 1.6 2003/07/27 11:03:24 nobu Exp $
$Id: enumerator.c 16614 2008-05-26 08:49:08Z knu $

************************************************/

#include "ruby/ruby.h"
#include "debug.h"

/*
* Document-class: Enumerable::Enumerator
*
* A class which provides a method `each' to be used as an Enumerable
* object.
*/
VALUE rb_cEnumerator;
static VALUE sym_each;

VALUE rb_eStopIteration;

struct enumerator {
    VALUE obj;
    ID meth;
    VALUE args;
    VALUE fib;
    VALUE dst;
    VALUE no_next;
};

static void
enumerator_mark(void *p)
{
#if !WITH_OBJC
    struct enumerator *ptr = p;
    rb_gc_mark(ptr->obj);
    rb_gc_mark(ptr->args);
    rb_gc_mark(ptr->fib);
    rb_gc_mark(ptr->dst);
#endif
}

static struct enumerator *
enumerator_ptr(VALUE obj)
{
    struct enumerator *ptr;

    Data_Get_Struct(obj, struct enumerator, ptr);
    if (RDATA(obj)->dmark != enumerator_mark) {
rb_raise(rb_eTypeError,
"wrong argument type %s (expected %s)",
rb_obj_classname(obj), rb_class2name(rb_cEnumerator));
    }
    if (!ptr) {
rb_raise(rb_eArgError, "uninitialized enumerator");
    }
    return ptr;
}

/*
* call-seq:
* obj.to_enum(method = :each, *args)
* obj.enum_for(method = :each, *args)
*
* Returns Enumerable::Enumerator.new(self, method, *args).
*
* e.g.:
*
* str = "xyz"
*
* enum = str.enum_for(:each_byte)
* a = enum.map {|b| '%02x' % b } #=> ["78", "79", "7a"]
*
* # protects an array from being modified
* a = [1, 2, 3]
* some_method(a.to_enum)
*
*/
static VALUE
obj_to_enum(int argc, VALUE *argv, VALUE obj)
{
    VALUE meth = sym_each;

    if (argc > 0) {
--argc;
meth = *argv++;
    }
    return rb_enumeratorize(obj, meth, argc, argv);
}

static VALUE
each_slice_i(VALUE val, VALUE *memo)
{
    VALUE ary = memo[0];
    VALUE v = Qnil;
    long size = (long)memo[1];

    rb_ary_push(ary, val);

    if (RARRAY_LEN(ary) == size) {
v = rb_yield(ary);
memo[0] = rb_ary_new2(size);
    }

    return v;
}

/*
* call-seq:
* e.each_slice(n) {...}
* e.each_slice(n)
*
* Iterates the given block for each slice of <n> elements. If no
* block is given, returns an enumerator.
*
* e.g.:
* (1..10).each_slice(3) {|a| p a}
* # outputs below
* [1, 2, 3]
* [4, 5, 6]
* [7, 8, 9]
* [10]
*
*/
static VALUE
enum_each_slice(VALUE obj, VALUE n)
{
    long size = NUM2LONG(n);
    VALUE args[2], ary;

    if (size <= 0) rb_raise(rb_eArgError, "invalid slice size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_slice_i, (VALUE)args);

    ary = args[0];
    if (RARRAY_LEN(ary) > 0) rb_yield(ary);

    return Qnil;
}

static VALUE
each_cons_i(VALUE val, VALUE *memo)
{
    VALUE ary = memo[0];
    VALUE v = Qnil;
    long size = (long)memo[1];

    if (RARRAY_LEN(ary) == size) {
rb_ary_shift(ary);
    }
    rb_ary_push(ary, val);
    if (RARRAY_LEN(ary) == size) {
v = rb_yield(rb_ary_dup(ary));
    }
    return v;
}

/*
* call-seq:
* each_cons(n) {...}
* each_cons(n)
*
* Iterates the given block for each array of consecutive <n>
* elements. If no block is given, returns an enumerator.a
*
* e.g.:
* (1..10).each_cons(3) {|a| p a}
* # outputs below
* [1, 2, 3]
* [2, 3, 4]
* [3, 4, 5]
* [4, 5, 6]
* [5, 6, 7]
* [6, 7, 8]
* [7, 8, 9]
* [8, 9, 10]
*
*/
static VALUE
enum_each_cons(VALUE obj, VALUE n)
{
    long size = NUM2LONG(n);
    VALUE args[2];

    if (size <= 0) rb_raise(rb_eArgError, "invalid size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_cons_i, (VALUE)args);

    return Qnil;
}

static VALUE
enumerator_allocate(VALUE klass)
{
    struct enumerator *ptr;
    return Data_Make_Struct(klass, struct enumerator,
enumerator_mark, -1, ptr);
}

static VALUE
enumerator_each_i(VALUE v, VALUE enum_obj, int argc, VALUE *argv)
{
    return rb_yield_values2(argc, argv);
}

static VALUE
enumerator_init(VALUE enum_obj, VALUE obj, VALUE meth, int argc, VALUE *argv)
{
    struct enumerator *ptr = enumerator_ptr(enum_obj);

    ptr->obj = obj;
    ptr->meth = rb_to_id(meth);
    if (argc) GC_WB(&ptr->args, rb_ary_new4(argc, argv));
    ptr->fib = 0;
    ptr->dst = Qnil;
    ptr->no_next = Qfalse;

    return enum_obj;
}

/*
* call-seq:
* Enumerable::Enumerator.new(obj, method = :each, *args)
*
* Creates a new Enumerable::Enumerator object, which is to be
* used as an Enumerable object using the given object's given
* method with the given arguments.
*
* Use of this method is not discouraged. Use Kernel#enum_for()
* instead.
*/
static VALUE
enumerator_initialize(int argc, VALUE *argv, VALUE obj)
{
    VALUE recv, meth = sym_each;

    if (argc == 0)
rb_raise(rb_eArgError, "wrong number of argument (0 for 1)");
    recv = *argv++;
    if (--argc) {
meth = *argv++;
--argc;
    }
    return enumerator_init(obj, recv, meth, argc, argv);
}

/* :nodoc: */
static VALUE
enumerator_init_copy(VALUE obj, VALUE orig)
{
    struct enumerator *ptr0, *ptr1;

    ptr0 = enumerator_ptr(orig);
    if (ptr0->fib) {
/* Fibers cannot be copied */
rb_raise(rb_eTypeError, "can't copy execution context");
    }
    ptr1 = enumerator_ptr(obj);

    ptr1->obj = ptr0->obj;
    ptr1->meth = ptr0->meth;
    ptr1->args = ptr0->args;
    ptr1->fib = 0;

    return obj;
}

VALUE
rb_enumeratorize(VALUE obj, VALUE meth, int argc, VALUE *argv)
{
    return enumerator_init(enumerator_allocate(rb_cEnumerator), obj, meth, argc, argv);
}

/*
* call-seq:
* enum.each {...}
*
* Iterates the given block using the object and the method specified
* in the first place. If no block is given, returns self.
*
*/
static VALUE
enumerator_each(VALUE obj)
{
    struct enumerator *e;
    int argc = 0;
    const VALUE *argv = 0;

    if (!rb_block_given_p()) return obj;
    e = enumerator_ptr(obj);
    if (e->args) {
argc = RARRAY_LEN(e->args);
argv = RARRAY_PTR(e->args);
    }
    return rb_block_call(e->obj, e->meth, argc, (VALUE *)argv,
enumerator_each_i, (VALUE)e);
}

static VALUE
enumerator_with_index_i(VALUE val, VALUE *memo)
{
    val = rb_yield_values(2, val, INT2FIX(*memo));
    ++*memo;
    return val;
}

/*
* call-seq:
* e.with_index {|(*args), idx| ... }
* e.with_index
*
* Iterates the given block for each elements with an index, which
* start from 0. If no block is given, returns an enumerator.
*
*/
static VALUE
enumerator_with_index(VALUE obj)
{
    struct enumerator *e;
    VALUE memo = 0;
    int argc = 0;
    const VALUE *argv = 0;

    RETURN_ENUMERATOR(obj, 0, 0);
    e = enumerator_ptr(obj);
    if (e->args) {
argc = RARRAY_LEN(e->args);
argv = RARRAY_PTR(e->args);
    }
    return rb_block_call(e->obj, e->meth, argc, (VALUE *)argv,
enumerator_with_index_i, (VALUE)&memo);
}

static VALUE
next_ii(VALUE i, VALUE obj, int argc, VALUE *argv)
{
    rb_fiber_yield(argc, argv);
    return Qnil;
}

static VALUE
next_i(VALUE curr, VALUE obj)
{
    struct enumerator *e = enumerator_ptr(obj);
    VALUE rnil = Qnil;

    rb_block_call(obj, rb_intern("each"), 0, 0, next_ii, obj);
    e->no_next = Qtrue;
    return rb_fiber_yield(1, &rnil);
}

static void
next_init(VALUE obj, struct enumerator *e)
{
    VALUE curr = rb_fiber_current();
    e->dst = curr;
    e->fib = rb_fiber_new(next_i, obj);
}

/*
* call-seq:
* e.next => object
*
* Returns the next object in the enumerator, and move the internal
* position forward. When the position reached at the end, internal
* position is rewinded then StopIteration is raised.
*
* Note that enumeration sequence by next method does not affect other
* non-external enumeration methods, unless underlying iteration
* methods itself has side-effect, e.g. IO#each_line.
*
*/

static VALUE
enumerator_next(VALUE obj)
{
    struct enumerator *e = enumerator_ptr(obj);
    VALUE curr, v;
    curr = rb_fiber_current();

    if (!e->fib || !rb_fiber_alive_p(e->fib)) {
next_init(obj, e);
    }

    v = rb_fiber_resume(e->fib, 1, &curr);
    if (e->no_next) {
e->fib = 0;
e->dst = Qnil;
e->no_next = Qfalse;
rb_raise(rb_eStopIteration, "iteration reached at end");
    }
    return v;
}

/*
* call-seq:
* e.rewind => e
*
* Rewinds the enumeration sequence by the next method.
*/

static VALUE
enumerator_rewind(VALUE obj)
{
    struct enumerator *e = enumerator_ptr(obj);

    e->fib = 0;
    e->dst = Qnil;
    e->no_next = Qfalse;
    return obj;
}

void
Init_Enumerator(void)
{
    rb_define_method(rb_mKernel, "to_enum", obj_to_enum, -1);
    rb_define_method(rb_mKernel, "enum_for", obj_to_enum, -1);

    rb_define_method(rb_mEnumerable, "each_slice", enum_each_slice, 1);
    rb_define_method(rb_mEnumerable, "each_cons", enum_each_cons, 1);

    rb_cEnumerator = rb_define_class_under(rb_mEnumerable, "Enumerator", rb_cObject);
    rb_include_module(rb_cEnumerator, rb_mEnumerable);

    rb_define_alloc_func(rb_cEnumerator, enumerator_allocate);
    rb_define_method(rb_cEnumerator, "initialize", enumerator_initialize, -1);
    rb_define_method(rb_cEnumerator, "initialize_copy", enumerator_init_copy, 1);
    rb_define_method(rb_cEnumerator, "each", enumerator_each, 0);
    rb_define_method(rb_cEnumerator, "each_with_index", enumerator_with_index, 0);
    rb_define_method(rb_cEnumerator, "with_index", enumerator_with_index, 0);
    rb_define_method(rb_cEnumerator, "next", enumerator_next, 0);
    rb_define_method(rb_cEnumerator, "rewind", enumerator_rewind, 0);

    rb_eStopIteration = rb_define_class("StopIteration", rb_eIndexError);

    sym_each = ID2SYM(rb_intern("each"));

    rb_provide("enumerator.so"); /* for backward compatibility */
}
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