import ast::*;
import std::option;
import std::option::some;
import std::option::none;
import codemap::span;


// Context-passing AST walker. Each overridden visit method has full control
// over what happens with its node, it can do its own traversal of the node's
// children (potentially passing in different contexts to each), call
// visit::visit_* to apply the default traversal algorithm (again, it can
// override the context), or prevent deeper traversal by doing nothing.

// Our typesystem doesn't do circular types, so the visitor record can not
// hold functions that take visitors. A vt tag is used to break the cycle.
tag vt[E] { mk_vt(visitor<E>); }

type visitor[E] =
    // takes the components so that one function can be
    // generic over constr and ty_constr
    @{visit_mod: fn(&_mod, &span, &E, &vt<E>),
      visit_view_item: fn(&@view_item, &E, &vt<E>),
      visit_native_item: fn(&@native_item, &E, &vt<E>),
      visit_item: fn(&@item, &E, &vt<E>),
      visit_local: fn(&@local, &E, &vt<E>),
      visit_block: fn(&ast::blk, &E, &vt<E>),
      visit_stmt: fn(&@stmt, &E, &vt<E>),
      visit_arm: fn(&arm, &E, &vt<E>),
      visit_pat: fn(&@pat, &E, &vt<E>),
      visit_decl: fn(&@decl, &E, &vt<E>),
      visit_expr: fn(&@expr, &E, &vt<E>),
      visit_ty: fn(&@ty, &E, &vt<E>),
      visit_constr: fn(&path, &span, node_id, &E, &vt<E>),
      visit_fn:
          fn(&_fn, &[ty_param], &span, &fn_ident, node_id, &E, &vt<E>) };

fn default_visitor[E]() -> visitor<E> {
    ret @{visit_mod: bind visit_mod[E](_, _, _, _),
          visit_view_item: bind visit_view_item[E](_, _, _),
          visit_native_item: bind visit_native_item[E](_, _, _),
          visit_item: bind visit_item[E](_, _, _),
          visit_local: bind visit_local[E](_, _, _),
          visit_block: bind visit_block[E](_, _, _),
          visit_stmt: bind visit_stmt[E](_, _, _),
          visit_arm: bind visit_arm[E](_, _, _),
          visit_pat: bind visit_pat[E](_, _, _),
          visit_decl: bind visit_decl[E](_, _, _),
          visit_expr: bind visit_expr[E](_, _, _),
          visit_ty: bind visit_ty[E](_, _, _),
          visit_constr: bind visit_constr[E](_, _, _, _, _),
          visit_fn: bind visit_fn[E](_, _, _, _, _, _, _)};
}

fn visit_crate[E](c: &crate, e: &E, v: &vt<E>) {
    v.visit_mod(c.node.module, c.span, e, v);
}

fn visit_crate_directive[E](cd: &@crate_directive, e: &E, v: &vt<E>) {
    alt cd.node {
      cdir_src_mod(_, _, _) { }
      cdir_dir_mod(_, _, cdirs, _) {
        for cdir: @crate_directive in cdirs {
            visit_crate_directive(cdir, e, v);
        }
      }
      cdir_view_item(vi) { v.visit_view_item(vi, e, v); }
      cdir_syntax(_) { }
      cdir_auth(_, _) { }
    }
}

fn visit_mod[E](m: &_mod, sp: &span, e: &E, v: &vt<E>) {
    for vi: @view_item in m.view_items { v.visit_view_item(vi, e, v); }
    for i: @item in m.items { v.visit_item(i, e, v); }
}

fn visit_view_item[E](vi: &@view_item, e: &E, v: &vt<E>) { }

fn visit_local[E](loc: &@local, e: &E, v: &vt<E>) {
    v.visit_pat(loc.node.pat, e, v);
    v.visit_ty(loc.node.ty, e, v);
    alt loc.node.init { none. { } some(i) { v.visit_expr(i.expr, e, v); } }
}

fn visit_item[E](i: &@item, e: &E, v: &vt<E>) {
    alt i.node {
      item_const(t, ex) { v.visit_ty(t, e, v); v.visit_expr(ex, e, v); }
      item_fn(f, tp) { v.visit_fn(f, tp, i.span, some(i.ident), i.id, e, v); }
      item_mod(m) { v.visit_mod(m, i.span, e, v); }
      item_native_mod(nm) {
        for vi: @view_item in nm.view_items { v.visit_view_item(vi, e, v); }
        for ni: @native_item in nm.items { v.visit_native_item(ni, e, v); }
      }
      item_ty(t, _) { v.visit_ty(t, e, v); }
      item_res(f, dtor_id, tps, _) {
        v.visit_fn(f, tps, i.span, some(i.ident), dtor_id, e, v);
      }
      item_tag(variants, _) {
        for vr: variant in variants {
            for va: variant_arg in vr.node.args { v.visit_ty(va.ty, e, v); }
        }
      }
      item_obj(ob, _, _) {
        for f: obj_field in ob.fields { v.visit_ty(f.ty, e, v); }
        for m: @method in ob.methods {
            v.visit_fn(m.node.meth, ~[], m.span, some(m.node.ident),
                       m.node.id, e, v);
        }
      }
    }
}

fn visit_ty[E](t: &@ty, e: &E, v: &vt<E>) {
    alt t.node {
      ty_nil. {/* no-op */ }
      ty_bot. {/* no-op */ }
      ty_bool. {/* no-op */ }
      ty_int. {/* no-op */ }
      ty_float. {/* no-op */ }
      ty_uint. {/* no-op */ }
      ty_machine(_) {/* no-op */ }
      ty_char. {/* no-op */ }
      ty_str. {/* no-op */ }
      ty_istr. {/* no-op */ }
      ty_box(mt) { v.visit_ty(mt.ty, e, v); }
      ty_vec(mt) { v.visit_ty(mt.ty, e, v); }
      ty_ivec(mt) { v.visit_ty(mt.ty, e, v); }
      ty_ptr(mt) { v.visit_ty(mt.ty, e, v); }
      ty_port(t) { v.visit_ty(t, e, v); }
      ty_chan(t) { v.visit_ty(t, e, v); }
      ty_task. {/* no-op */ }
      ty_rec(flds) {
        for f: ty_field in flds { v.visit_ty(f.node.mt.ty, e, v); }
      }
      ty_tup(ts) {
        for tt in ts { v.visit_ty(tt, e, v); }
      }
      ty_fn(_, args, out, _, constrs) {
        for a: ty_arg in args { v.visit_ty(a.node.ty, e, v); }
        for c: @constr in constrs {
            v.visit_constr(c.node.path, c.span, c.node.id, e, v);
        }
        v.visit_ty(out, e, v);
      }
      ty_obj(tmeths) {
        for m: ty_method in tmeths {
            for a: ty_arg in m.node.inputs { v.visit_ty(a.node.ty, e, v); }
            v.visit_ty(m.node.output, e, v);
        }
      }
      ty_path(p, _) { for tp: @ty in p.node.types { v.visit_ty(tp, e, v); } }
      ty_type. {/* no-op */ }
      ty_constr(t, cs) {
        v.visit_ty(t, e, v);
        for tc: @spanned<constr_general_<path, node_id>> in cs {
            v.visit_constr(tc.node.path, tc.span, tc.node.id, e, v);
        }
      }
      ty_infer. {/* no-op */ }
    }
}

fn visit_constr[E](operator: &path, sp: &span, id: node_id, e: &E,
                   v: &vt<E>) {
    // default
}

fn visit_pat[E](p: &@pat, e: &E, v: &vt<E>) {
    alt p.node {
      pat_tag(path, children) {
        for tp: @ty in path.node.types { v.visit_ty(tp, e, v); }
        for child: @pat in children { v.visit_pat(child, e, v); }
      }
      pat_rec(fields, _) {
        for f: field_pat in fields { v.visit_pat(f.pat, e, v); }
      }
      pat_tup(elts) {
        for elt in elts { v.visit_pat(elt, e, v); }
      }
      pat_box(inner) { v.visit_pat(inner, e, v); }
      _ { }
    }
}

fn visit_native_item[E](ni: &@native_item, e: &E, v: &vt<E>) {
    alt ni.node {
      native_item_fn(_, fd, _) { visit_fn_decl(fd, e, v); }
      native_item_ty. { }
    }
}

fn visit_fn_decl[E](fd: &fn_decl, e: &E, v: &vt<E>) {
    for a: arg in fd.inputs { v.visit_ty(a.ty, e, v); }
    for c: @constr in fd.constraints {
        v.visit_constr(c.node.path, c.span, c.node.id, e, v);
    }
    v.visit_ty(fd.output, e, v);
}

fn visit_fn[E](f: &_fn, tp: &[ty_param], sp: &span, i: &fn_ident, id: node_id,
               e: &E, v: &vt<E>) {
    visit_fn_decl(f.decl, e, v);
    v.visit_block(f.body, e, v);
}

fn visit_block[E](b: &ast::blk, e: &E, v: &vt<E>) {
    for s: @stmt in b.node.stmts { v.visit_stmt(s, e, v); }
    visit_expr_opt(b.node.expr, e, v);
}

fn visit_stmt[E](s: &@stmt, e: &E, v: &vt<E>) {
    alt s.node {
      stmt_decl(d, _) { v.visit_decl(d, e, v); }
      stmt_expr(ex, _) { v.visit_expr(ex, e, v); }
      stmt_crate_directive(cd) { visit_crate_directive(cd, e, v); }
    }
}

fn visit_decl[E](d: &@decl, e: &E, v: &vt<E>) {
    alt d.node {
      decl_local(locs) {
        for loc: @ast::local in locs { v.visit_local(loc, e, v); }
      }
      decl_item(it) { v.visit_item(it, e, v); }
    }
}

fn visit_expr_opt[E](eo: option::t<@expr>, e: &E, v: &vt<E>) {
    alt eo { none. { } some(ex) { v.visit_expr(ex, e, v); } }
}

fn visit_exprs[E](exprs: &[@expr], e: &E, v: &vt<E>) {
    for ex: @expr in exprs { v.visit_expr(ex, e, v); }
}

fn visit_mac[E](m: mac, e: &E, v: &vt<E>) {
    alt m.node {
      ast::mac_invoc(pth, arg, body) { visit_expr(arg, e, v); }
      ast::mac_embed_type(ty) { v.visit_ty(ty, e, v); }
      ast::mac_embed_block(blk) { v.visit_block(blk, e, v); }
      ast::mac_ellipsis. { }
    }
}

fn visit_expr[E](ex: &@expr, e: &E, v: &vt<E>) {
    alt ex.node {
      expr_vec(es, _, _) { visit_exprs(es, e, v); }
      expr_rec(flds, base) {
        for f: field in flds { v.visit_expr(f.node.expr, e, v); }
        visit_expr_opt(base, e, v);
      }
      expr_tup(elts) {
        for el in elts { v.visit_expr(el, e, v); }
      }
      expr_call(callee, args) {
        v.visit_expr(callee, e, v);
        visit_exprs(args, e, v);
      }
      expr_self_method(_) { }
      expr_bind(callee, args) {
        v.visit_expr(callee, e, v);
        for eo: option::t<@expr> in args { visit_expr_opt(eo, e, v); }
      }
      expr_binary(_, a, b) { v.visit_expr(a, e, v); v.visit_expr(b, e, v); }
      expr_unary(_, a) { v.visit_expr(a, e, v); }
      expr_lit(_) { }
      expr_cast(x, t) { v.visit_expr(x, e, v); v.visit_ty(t, e, v); }
      expr_if(x, b, eo) {
        v.visit_expr(x, e, v);
        v.visit_block(b, e, v);
        visit_expr_opt(eo, e, v);
      }
      expr_if_check(x, b, eo) {
        v.visit_expr(x, e, v);
        v.visit_block(b, e, v);
        visit_expr_opt(eo, e, v);
      }
      expr_ternary(c, t, el) {
        v.visit_expr(c, e, v);
        v.visit_expr(t, e, v);
        v.visit_expr(el, e, v);
      }
      expr_while(x, b) { v.visit_expr(x, e, v); v.visit_block(b, e, v); }
      expr_for(dcl, x, b) | expr_for_each(dcl, x, b) {
        v.visit_local(dcl, e, v);
        v.visit_expr(x, e, v);
        v.visit_block(b, e, v);
      }
      expr_do_while(b, x) { v.visit_block(b, e, v); v.visit_expr(x, e, v); }
      expr_alt(x, arms) {
        v.visit_expr(x, e, v);
        for a: arm in arms { v.visit_arm(a, e, v); }
      }
      expr_fn(f) { v.visit_fn(f, ~[], ex.span, none, ex.id, e, v); }
      expr_block(b) { v.visit_block(b, e, v); }
      expr_assign(a, b) { v.visit_expr(b, e, v); v.visit_expr(a, e, v); }
      expr_copy(a) { v.visit_expr(a, e, v); }
      expr_move(a, b) { v.visit_expr(b, e, v); v.visit_expr(a, e, v); }
      expr_swap(a, b) { v.visit_expr(a, e, v); v.visit_expr(b, e, v); }
      expr_assign_op(_, a, b) {
        v.visit_expr(b, e, v);
        v.visit_expr(a, e, v);
      }
      expr_field(x, _) { v.visit_expr(x, e, v); }
      expr_index(a, b) { v.visit_expr(a, e, v); v.visit_expr(b, e, v); }
      expr_path(p) { for tp: @ty in p.node.types { v.visit_ty(tp, e, v); } }
      expr_fail(eo) { visit_expr_opt(eo, e, v); }
      expr_break. { }
      expr_cont. { }
      expr_ret(eo) { visit_expr_opt(eo, e, v); }
      expr_put(eo) { visit_expr_opt(eo, e, v); }
      expr_be(x) { v.visit_expr(x, e, v); }
      expr_log(_, x) { v.visit_expr(x, e, v); }
      expr_check(_, x) { v.visit_expr(x, e, v); }
      expr_assert(x) { v.visit_expr(x, e, v); }
      expr_anon_obj(anon_obj) {
        alt anon_obj.fields {
          none. { }
          some(fields) {
            for f: anon_obj_field in fields {
                v.visit_ty(f.ty, e, v);
                v.visit_expr(f.expr, e, v);
            }
          }
        }
        alt anon_obj.inner_obj {
          none. { }
          some(ex) { v.visit_expr(ex, e, v); }
        }
        for m: @method in anon_obj.methods {
            v.visit_fn(m.node.meth, ~[], m.span, some(m.node.ident),
                       m.node.id, e, v);
        }
      }
      expr_mac(mac) { visit_mac(mac, e, v); }
      expr_uniq(x) { v.visit_expr(x, e, v); }
    }
}

fn visit_arm[E](a: &arm, e: &E, v: &vt<E>) {
    for p: @pat in a.pats { v.visit_pat(p, e, v); }
    v.visit_block(a.body, e, v);
}

// Simpler, non-context passing interface. Always walks the whole tree, simply
// calls the given functions on the nodes.

type simple_visitor =
    // takes the components so that one function can be
    // generic over constr and ty_constr
    @{visit_mod: fn(&_mod, &span) ,
      visit_view_item: fn(&@view_item) ,
      visit_native_item: fn(&@native_item) ,
      visit_item: fn(&@item) ,
      visit_local: fn(&@local) ,
      visit_block: fn(&ast::blk) ,
      visit_stmt: fn(&@stmt) ,
      visit_arm: fn(&arm) ,
      visit_pat: fn(&@pat) ,
      visit_decl: fn(&@decl) ,
      visit_expr: fn(&@expr) ,
      visit_ty: fn(&@ty) ,
      visit_constr: fn(&path, &span, node_id) ,
      visit_fn: fn(&_fn, &[ty_param], &span, &fn_ident, node_id) };

fn default_simple_visitor() -> simple_visitor {
    ret @{visit_mod: fn (m: &_mod, sp: &span) { },
          visit_view_item: fn (vi: &@view_item) { },
          visit_native_item: fn (ni: &@native_item) { },
          visit_item: fn (i: &@item) { },
          visit_local: fn (l: &@local) { },
          visit_block: fn (b: &ast::blk) { },
          visit_stmt: fn (s: &@stmt) { },
          visit_arm: fn (a: &arm) { },
          visit_pat: fn (p: &@pat) { },
          visit_decl: fn (d: &@decl) { },
          visit_expr: fn (e: &@expr) { },
          visit_ty: fn (t: &@ty) { },
          visit_constr: fn (p: &path, sp: &span, id: node_id) { },
          visit_fn:
              fn (f: &_fn, tps: &[ty_param], sp: &span, ident: &fn_ident,
                  id: node_id) {
              }};
}

fn mk_simple_visitor(v: &simple_visitor) -> vt<()> {
    fn v_mod(f: fn(&_mod, &span) , m: &_mod, sp: &span, e: &(), v: &vt<()>) {
        f(m, sp);
        visit_mod(m, sp, e, v);
    }
    fn v_view_item(f: fn(&@view_item) , vi: &@view_item, e: &(), v: &vt<()>) {
        f(vi);
        visit_view_item(vi, e, v);
    }
    fn v_native_item(f: fn(&@native_item) , ni: &@native_item, e: &(),
                     v: &vt<()>) {
        f(ni);
        visit_native_item(ni, e, v);
    }
    fn v_item(f: fn(&@item) , i: &@item, e: &(), v: &vt<()>) {
        f(i);
        visit_item(i, e, v);
    }
    fn v_local(f: fn(&@local) , l: &@local, e: &(), v: &vt<()>) {
        f(l);
        visit_local(l, e, v);
    }
    fn v_block(f: fn(&ast::blk) , bl: &ast::blk, e: &(), v: &vt<()>) {
        f(bl);
        visit_block(bl, e, v);
    }
    fn v_stmt(f: fn(&@stmt) , st: &@stmt, e: &(), v: &vt<()>) {
        f(st);
        visit_stmt(st, e, v);
    }
    fn v_arm(f: fn(&arm) , a: &arm, e: &(), v: &vt<()>) {
        f(a);
        visit_arm(a, e, v);
    }
    fn v_pat(f: fn(&@pat) , p: &@pat, e: &(), v: &vt<()>) {
        f(p);
        visit_pat(p, e, v);
    }
    fn v_decl(f: fn(&@decl) , d: &@decl, e: &(), v: &vt<()>) {
        f(d);
        visit_decl(d, e, v);
    }
    fn v_expr(f: fn(&@expr) , ex: &@expr, e: &(), v: &vt<()>) {
        f(ex);
        visit_expr(ex, e, v);
    }
    fn v_ty(f: fn(&@ty) , ty: &@ty, e: &(), v: &vt<()>) {
        f(ty);
        visit_ty(ty, e, v);
    }
    fn v_constr(f: fn(&path, &span, node_id) , pt: &path, sp: &span,
                id: node_id, e: &(), v: &vt<()>) {
        f(pt, sp, id);
        visit_constr(pt, sp, id, e, v);
    }
    fn v_fn(f: fn(&_fn, &[ty_param], &span, &fn_ident, node_id) , ff: &_fn,
            tps: &[ty_param], sp: &span, ident: &fn_ident, id: node_id,
            e: &(), v: &vt<()>) {
        f(ff, tps, sp, ident, id);
        visit_fn(ff, tps, sp, ident, id, e, v);
    }
    ret mk_vt(@{visit_mod: bind v_mod(v.visit_mod, _, _, _, _),
                visit_view_item: bind v_view_item(v.visit_view_item, _, _, _),
                visit_native_item:
                    bind v_native_item(v.visit_native_item, _, _, _),
                visit_item: bind v_item(v.visit_item, _, _, _),
                visit_local: bind v_local(v.visit_local, _, _, _),
                visit_block: bind v_block(v.visit_block, _, _, _),
                visit_stmt: bind v_stmt(v.visit_stmt, _, _, _),
                visit_arm: bind v_arm(v.visit_arm, _, _, _),
                visit_pat: bind v_pat(v.visit_pat, _, _, _),
                visit_decl: bind v_decl(v.visit_decl, _, _, _),
                visit_expr: bind v_expr(v.visit_expr, _, _, _),
                visit_ty: bind v_ty(v.visit_ty, _, _, _),
                visit_constr: bind v_constr(v.visit_constr, _, _, _, _, _),
                visit_fn: bind v_fn(v.visit_fn, _, _, _, _, _, _, _)});
}

// 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: