import option::none;
import option::some;
import util::orb;

type vbuf = rustrt::vbuf;

type operator2[T, U, V] = fn(&T, &U) -> V ;

type array[T] = vec[mutable? T];

native "rust" mod rustrt {
    type vbuf;
    fn vec_buf[T](vec[T] v, uint offset) -> vbuf;
    fn vec_len[T](vec[T] v) -> uint;

        /**
         * Sometimes we modify the vec internal data via vec_buf and need to
         * update the vec's fill length accordingly.
         */
        fn vec_len_set[T](vec[T] v, uint n);

        /**
         * The T in vec_alloc[T, U] is the type of the vec to allocate.  The
         * U is the type of an element in the vec.  So to allocate a vec[U] we
         * want to invoke this as vec_alloc[vec[U], U].
         */
        fn vec_alloc[T, U](uint n_elts) -> vec[U];
    fn vec_alloc_mut[T, U](uint n_elts) -> vec[mutable U];
    fn refcount[T](vec[T] v) -> uint;
    fn vec_print_debug_info[T](vec[T] v);
    fn vec_from_vbuf[T](vbuf v, uint n_elts) -> vec[T];
    fn unsafe_vec_to_mut[T](vec[T] v) -> vec[mutable T];
}

fn alloc[T](uint n_elts) -> vec[T] {
    ret rustrt::vec_alloc[vec[T], T](n_elts);
}

fn alloc_mut[T](uint n_elts) -> vec[mutable T] {
    ret rustrt::vec_alloc_mut[vec[mutable T], T](n_elts);
}

fn refcount[T](array[T] v) -> uint {
    auto r = rustrt::refcount[T](v);
    if (r == dbg::const_refcount) {
        ret r;
    } else {
        // -2 because calling this function and the native function both
        // incremented the refcount.

        ret r - 2u;
    }
}

fn vec_from_vbuf[T](vbuf v, uint n_elts) -> vec[T] {
    ret rustrt::vec_from_vbuf[T](v, n_elts);
}


// FIXME: Remove me; this is a botch to get around rustboot's bad typechecker.
fn empty[T]() -> vec[T] { ret alloc[T](0u); }


// FIXME: Remove me; this is a botch to get around rustboot's bad typechecker.
fn empty_mut[T]() -> vec[mutable T] { ret alloc_mut[T](0u); }

type init_op[T] = fn(uint) -> T ;

fn init_fn[T](&init_op[T] op, uint n_elts) -> vec[T] {
    let vec[T] v = alloc[T](n_elts);
    let uint i = 0u;
    while (i < n_elts) { v += [op(i)]; i += 1u; }
    ret v;
}

fn init_fn_mut[T](&init_op[T] op, uint n_elts) -> vec[mutable T] {
    let vec[mutable T] v = alloc_mut[T](n_elts);
    let uint i = 0u;
    while (i < n_elts) { v += [mutable op(i)]; i += 1u; }
    ret v;
}

// init_elt: creates and returns a vector of length n_elts, filled with
// that many copies of element t.
fn init_elt[T](&T t, uint n_elts) -> vec[T] {
    /**
     * FIXME (issue #81): should be:
     *
     * fn elt_op[T](&T x, uint i) -> T { ret x; }
     * let init_op[T] inner = bind elt_op[T](t, _);
     * ret init_fn[T](inner, n_elts);
     */

    let vec[T] v = alloc[T](n_elts);
    let uint i = n_elts;
    while (i > 0u) { i -= 1u; v += [t]; }
    ret v;
}

fn init_elt_mut[T](&T t, uint n_elts) -> vec[mutable T] {
    let vec[mutable T] v = alloc_mut[T](n_elts);
    let uint i = n_elts;
    while (i > 0u) { i -= 1u; v += [mutable t]; }
    ret v;
}

fn buf[T](array[T] v) -> vbuf { ret rustrt::vec_buf[T](v, 0u); }

fn len[T](array[T] v) -> uint { ret rustrt::vec_len[T](v); }

fn len_set[T](array[T] v, uint n) { rustrt::vec_len_set[T](v, n); }

fn buf_off[T](array[T] v, uint offset) -> vbuf {
    assert (offset < len[T](v));
    ret rustrt::vec_buf[T](v, offset);
}

fn print_debug_info[T](array[T] v) { rustrt::vec_print_debug_info[T](v); }

// FIXME: typestate precondition (list is non-empty)
// Returns the last element of v.
fn last[T](array[T] v) -> option::t[T] {
    auto l = len[T](v);
    if (l == 0u) { ret none[T]; }
    ret some[T](v.(l - 1u));
}


// Returns elements from [start..end) from v.
fn slice[T](array[T] v, uint start, uint end) -> vec[T] {
    assert (start <= end);
    assert (end <= len[T](v));
    auto result = alloc[T](end - start);
    let uint i = start;
    while (i < end) { result += [v.(i)]; i += 1u; }
    ret result;
}


// FIXME: Should go away eventually.
fn slice_mut[T](array[T] v, uint start, uint end) -> vec[mutable T] {
    assert (start <= end);
    assert (end <= len[T](v));
    auto result = alloc_mut[T](end - start);
    let uint i = start;
    while (i < end) { result += [mutable v.(i)]; i += 1u; }
    ret result;
}

fn shift[T](&mutable array[T] v) -> T {
    auto ln = len[T](v);
    assert (ln > 0u);
    auto e = v.(0);
    v = slice[T](v, 1u, ln);
    ret e;
}

fn pop[T](&mutable array[T] v) -> T {
    auto ln = len[T](v);
    assert (ln > 0u);
    ln -= 1u;
    auto e = v.(ln);
    v = slice[T](v, 0u, ln);
    ret e;
}

fn top[T](&array[T] v) -> T {
    auto ln = len[T](v);
    assert (ln > 0u);
    ret v.(ln - 1u);
}

fn push[T](&mutable array[T] v, &T t) { v += [t]; }

fn unshift[T](&mutable array[T] v, &T t) {
    auto rs = alloc[T](len[T](v) + 1u);
    rs += [t];
    rs += v;
    v = rs;
}

fn grow[T](&mutable array[T] v, uint n, &T initval) {
    let uint i = n;
    while (i > 0u) { i -= 1u; v += [initval]; }
}

fn grow_set[T](&mutable vec[mutable T] v, uint index, &T initval, &T val) {
    auto length = vec::len(v);
    if (index >= length) { grow(v, index - length + 1u, initval); }
    v.(index) = val;
}

fn grow_init_fn[T](&mutable array[T] v, uint n, fn() -> T  init_fn) {
    let uint i = n;
    while (i > 0u) { i -= 1u; v += [init_fn()]; }
}

fn grow_init_fn_set[T](&array[T] v, uint index, fn() -> T  init_fn, &T val) {
    auto length = vec::len(v);
    if (index >= length) { grow_init_fn(v, index - length + 1u, init_fn); }
    v.(index) = val;
}

fn map[T, U](&fn(&T) -> U  f, &vec[T] v) -> vec[U] {
    let vec[U] rs = alloc[U](len[T](v));
    for (T ve in v) { rs += [f(ve)]; }
    ret rs;
}

fn filter_map[T, U](&fn(&T) -> option::t[U]  f, &vec[T] v) -> vec[U] {
    let vec[U] rs = [];
    for (T ve in v) {
        alt (f(ve)) { case (some(?elt)) { rs += [elt]; } case (none) { } }
    }
    ret rs;
}

fn map2[T, U, V](&operator2[T, U, V] f, &vec[T] v0, &vec[U] v1) -> vec[V] {
    auto v0_len = len[T](v0);
    if (v0_len != len[U](v1)) { fail; }
    let vec[V] u = alloc[V](v0_len);
    auto i = 0u;
    while (i < v0_len) { u += [f({ v0.(i) }, { v1.(i) })]; i += 1u; }
    ret u;
}

fn find[T](fn(&T) -> bool  f, &vec[T] v) -> option::t[T] {
    for (T elt in v) { if (f(elt)) { ret some[T](elt); } }
    ret none[T];
}

fn position[T](&T x, &array[T] v) -> option::t[uint] {
    let uint i = 0u;
    while (i < len(v)) {
        if (x == v.(i)) { ret some[uint](i); }
        i += 1u;
    }
    ret none[uint];
}

fn position_pred[T](fn (&T) -> bool f, &vec[T] v) -> option::t[uint] {
    let uint i = 0u;
    while (i < len(v)) {
        if (f(v.(i))) { ret some[uint](i); }
        i += 1u;
    }
    ret none[uint];
}

fn member[T](&T x, &array[T] v) -> bool {
    for (T elt in v) { if (x == elt) { ret true; } }
    ret false;
}

fn count[T](&T x, &array[T] v) -> uint {
    auto cnt = 0u;
    for (T elt in v) { if (x == elt) { cnt += 1u; } }
    ret cnt;
}

fn foldl[T, U](fn(&U, &T) -> U  p, &U z, &vec[T] v) -> U {
    auto sz = len[T](v);
    if (sz == 0u) {
        ret z;
    } else {
        auto rest = slice[T](v, 1u, sz);
        ret p(foldl[T, U](p, z, rest), v.(0));
    }
}

fn unzip[T, U](&vec[tup(T, U)] v) -> tup(vec[T], vec[U]) {
    auto sz = len[tup(T, U)](v);
    if (sz == 0u) {
        ret tup(alloc[T](0u), alloc[U](0u));
    } else {
        auto rest = slice[tup(T, U)](v, 1u, sz);
        auto tl = unzip[T, U](rest);
        auto a = [v.(0)._0];
        auto b = [v.(0)._1];
        ret tup(a + tl._0, b + tl._1);
    }
}


// FIXME make the lengths being equal a constraint
fn zip[T, U](&vec[T] v, &vec[U] u) -> vec[tup(T, U)] {
    auto sz = len[T](v);
    assert (sz == len[U](u));
    if (sz == 0u) {
        ret alloc[tup(T, U)](0u);
    } else {
        auto rest = zip[T, U](slice[T](v, 1u, sz), slice[U](u, 1u, sz));
        vec::push(rest, tup(v.(0), u.(0)));
        ret rest;
    }
}

fn or(&vec[bool] v) -> bool {
    auto f = orb;
    ret vec::foldl[bool, bool](f, false, v);
}

fn any[T](&fn(&T) -> bool f, &vec[T] v) -> bool {
    for (T t in v) {
        if (f(t)) { ret true; } 
    }
    ret false;
}
fn all[T](&fn(&T) -> bool f, &vec[T] v) -> bool {
    for (T t in v) {
        if (!f(t)) { ret false; } 
    }
    ret true;
}

fn clone[T](&vec[T] v) -> vec[T] { ret slice[T](v, 0u, len[T](v)); }

fn plus_option[T](&mutable vec[T] v, &option::t[T] o) {
    alt (o) { case (none) { } case (some(?x)) { v += [x]; } }
}

fn cat_options[T](&vec[option::t[T]] v) -> vec[T] {
    let vec[T] rs = [];
    for (option::t[T] o in v) {
        alt (o) { case (none) { } case (some(?t)) { rs += [t]; } }
    }
    ret rs;
}


// TODO: Remove in favor of built-in "freeze" operation when it's implemented.
fn freeze[T](vec[mutable T] v) -> vec[T] {
    let vec[T] result = [];
    for (T elem in v) { result += [elem]; }
    ret result;
}


// Swaps two elements in a vector
fn swap[T](&vec[mutable T] v, uint a, uint b) {
    let T t = v.(a);
    v.(a) = v.(b);
    v.(b) = t;
}


// In place vector reversal
fn reverse[T](&vec[mutable T] v) {
    let uint i = 0u;
    auto ln = len[T](v);
    while (i < ln / 2u) { swap(v, i, ln - i - 1u); i += 1u; }
}


// Functional vector reversal. Returns a reversed copy of v.
fn reversed[T](vec[T] v) -> vec[T] {
    let vec[T] rs = [];
    auto i = len[T](v);
    if (i == 0u) { ret rs; } else { i -= 1u; }
    while (i != 0u) { push[T](rs, v.(i)); i -= 1u; }
    push[T](rs, v.(0));
    ret rs;
}


/// Truncates the vector to length `new_len`.
/// FIXME: This relies on a typechecker bug (covariance vs. invariance).
fn truncate[T](&mutable vec[mutable? T] v, uint new_len) {
    v = slice[T](v, 0u, new_len);
}
// Local Variables:
// mode: rust;
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End: