/*
Copyright (c) 2016 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.

Author: Leonardo de Moura
*/
#include "util/timeit.h"
#include "kernel/type_checker.h"
#include "kernel/declaration.h"
#include "library/trace.h"
#include "library/explicit.h"
#include "library/typed_expr.h"
#include "library/private.h"
#include "library/protected.h"
#include "library/scoped_ext.h"
#include "library/noncomputable.h"
#include "library/module.h"
#include "library/flycheck.h"
#include "library/error_handling.h"
#include "library/scope_pos_info_provider.h"
#include "library/equations_compiler/equations.h"
#include "library/compiler/vm_compiler.h"
#include "frontends/lean/parser.h"
#include "frontends/lean/tokens.h"
#include "frontends/lean/elaborator.h"
#include "frontends/lean/util.h"
#include "frontends/lean/decl_util.h"
#include "frontends/lean/decl_attributes.h"
#include "frontends/lean/definition_cmds.h"

// We don't display profiling information for declarations that take less than 0.01 secs
#ifndef LEAN_PROFILE_THRESHOLD
#define LEAN_PROFILE_THRESHOLD 0.01
#endif

namespace lean {
environment ensure_decl_namespaces(environment const & env, name const & full_n) {
    if (full_n.is_atomic())
        return env;
    return add_namespace(env, full_n.get_prefix());
}

expr parse_equation_lhs(parser & p, expr const & fn, buffer<expr> & locals) {
    auto lhs_pos = p.pos();
    buffer<expr> lhs_args;
    lhs_args.push_back(p.parse_pattern_or_expr(get_max_prec()));
    while (!p.curr_is_token(get_assign_tk())) {
        lhs_args.push_back(p.parse_pattern_or_expr(get_max_prec()));
    }
    expr lhs = p.mk_app(p.save_pos(mk_explicit(fn), lhs_pos), lhs_args, lhs_pos);
    bool skip_main_fn = true;
    return p.patexpr_to_pattern(lhs, skip_main_fn, locals);
}

expr parse_equation(parser & p, expr const & fn) {
    p.check_token_next(get_bar_tk(), "invalid equation, '|' expected");
    buffer<expr> locals;
    expr lhs = parse_equation_lhs(p, fn, locals);
    auto assign_pos = p.pos();
    p.check_token_next(get_assign_tk(), "invalid equation, ':=' expected");
    expr rhs = p.parse_scoped_expr(locals);
    return Fun(locals, p.save_pos(mk_equation(lhs, rhs), assign_pos), p);
}

optional<expr_pair> parse_using_well_founded(parser & p) {
    if (p.curr_is_token(get_using_well_founded_tk())) {
        p.next();
        expr R   = p.parse_expr(get_max_prec());
        expr Rwf = p.parse_expr(get_max_prec());
        return optional<expr_pair>(R, Rwf);
    } else {
        return optional<expr_pair>();
    }
}

expr mk_equations(parser & p, buffer<expr> const & fns, buffer<name> const & fn_full_names, buffer<expr> const & eqs,
                  optional<expr_pair> const & R_Rwf, pos_info const & pos) {
    buffer<expr> new_eqs;
    for (expr const & eq : eqs) {
        new_eqs.push_back(Fun(fns, eq, p));
    }
    equations_header h = mk_equations_header(to_list(fn_full_names));
    if (R_Rwf) {
        return p.save_pos(mk_equations(h, new_eqs.size(), new_eqs.data(), R_Rwf->first, R_Rwf->second), pos);
    } else {
        return p.save_pos(mk_equations(h, new_eqs.size(), new_eqs.data()), pos);
    }
}

expr mk_equations(parser & p, expr const & fn, name const & full_name, buffer<expr> const & eqs,
                  optional<expr_pair> const & R_Rwf, pos_info const & pos) {
    buffer<expr> fns; fns.push_back(fn);
    buffer<name> full_names; full_names.push_back(full_name);
    return mk_equations(p, fns, full_names, eqs, R_Rwf, pos);
}

expr parse_mutual_definition(parser & p, buffer<name> & lp_names, buffer<expr> & fns, buffer<expr> & params) {
    parser::local_scope scope1(p);
    auto header_pos = p.pos();
    buffer<expr> pre_fns;
    parse_mutual_header(p, lp_names, pre_fns, params);
    buffer<expr> eqns;
    buffer<name> full_names;
    for (expr const & pre_fn : pre_fns) {
        // TODO(leo, dhs): make use of attributes
        expr fn_type = parse_inner_header(p, local_pp_name(pre_fn)).first;
        declaration_name_scope scope2(local_pp_name(pre_fn));
        declaration_name_scope scope3("_main");
        full_names.push_back(scope2.get_name());
        if (p.curr_is_token(get_none_tk())) {
            auto none_pos = p.pos();
            p.next();
            eqns.push_back(p.save_pos(mk_no_equation(), none_pos));
        } else {
            while (p.curr_is_token(get_bar_tk())) {
                eqns.push_back(parse_equation(p, pre_fn));
            }
        }
        expr fn      = mk_local(mlocal_name(pre_fn), local_pp_name(pre_fn), fn_type, mk_rec_info(true));
        fns.push_back(fn);
    }
    if (p.curr_is_token(get_with_tk()))
        throw parser_error("unexpected 'with' clause", p.pos());
    optional<expr_pair> R_Rwf = parse_using_well_founded(p);
    for (expr & eq : eqns) {
        eq = replace_locals(eq, pre_fns, fns);
    }
    expr r = mk_equations(p, fns, full_names, eqns, R_Rwf, header_pos);
    collect_implicit_locals(p, lp_names, params, r);
    return r;
}

environment mutual_definition_cmd_core(parser & p, def_cmd_kind kind, bool is_private, bool /* is_protected */, bool is_noncomputable,
                                       decl_attributes /* attrs */) {
    buffer<name> lp_names;
    buffer<expr> fns, params;
    declaration_info_scope scope(p.env(), is_private, is_noncomputable, kind);
    expr val = parse_mutual_definition(p, lp_names, fns, params);
    if (p.used_sorry()) p.declare_sorry();
    elaborator elab(p.env(), p.get_options(), metavar_context(), local_context());
    buffer<expr> new_params;
    elaborate_params(elab, params, new_params);
    val = replace_locals(val, params, new_params);

    // TODO(Leo)
    for (auto p : new_params) { tout() << ">> " << p << " : " << mlocal_type(p) << "\n"; }
    tout() << val << "\n";

    return p.env();
}

static expr_pair parse_definition(parser & p, buffer<name> & lp_names, buffer<expr> & params, bool is_example) {
    parser::local_scope scope1(p);
    auto header_pos = p.pos();
    expr fn = parse_single_header(p, lp_names, params, is_example);
    declaration_name_scope scope2(local_pp_name(fn));
    expr val;
    if (p.curr_is_token(get_assign_tk())) {
        p.next();
        val = p.parse_expr();
    } else if (p.curr_is_token(get_bar_tk()) || p.curr_is_token(get_none_tk())) {
        declaration_name_scope scope2("_main");
        fn = mk_local(mlocal_name(fn), local_pp_name(fn), mlocal_type(fn), mk_rec_info(true));
        p.add_local(fn);
        buffer<expr> eqns;
        if (p.curr_is_token(get_none_tk())) {
            auto none_pos = p.pos();
            p.next();
            eqns.push_back(p.save_pos(mk_no_equation(), none_pos));
        } else {
            while (p.curr_is_token(get_bar_tk())) {
                eqns.push_back(parse_equation(p, fn));
            }
        }
        optional<expr_pair> R_Rwf = parse_using_well_founded(p);
        val = mk_equations(p, fn, scope2.get_name(), eqns, R_Rwf, header_pos);
    } else {
        throw parser_error("invalid definition, '|' or ':=' expected", p.pos());
    }
    collect_implicit_locals(p, lp_names, params, {mlocal_type(fn), val});
    return mk_pair(fn, val);
}

static void replace_params(buffer<expr> const & params, buffer<expr> const & new_params, expr & fn, expr & val) {
    expr fn_type = replace_locals(mlocal_type(fn), params, new_params);
    expr new_fn  = update_mlocal(fn, fn_type);
    val          = replace_locals(val, params, new_params);
    val          = replace_local(val, fn, new_fn);
    fn           = new_fn;
}

static expr_pair elaborate_theorem(elaborator & elab, expr const & fn, expr val) {
    expr fn_type = elab.elaborate_type(mlocal_type(fn));
    expr new_fn  = update_mlocal(fn, fn_type);
    val = replace_local(val, fn, new_fn);
    return elab.elaborate_with_type(val, mk_as_is(fn_type));
}

static expr_pair elaborate_definition_core(elaborator & elab, def_cmd_kind kind, expr const & fn, expr const & val) {
    if (kind == Theorem) {
        return elaborate_theorem(elab, fn, val);
    } else {
        return elab.elaborate_with_type(val, mlocal_type(fn));
    }
}

static void display_pos(std::ostream & out, parser const & p, pos_info const & pos) {
    display_pos(out, p.get_stream_name().c_str(), pos.first, pos.second);
}

static expr_pair elaborate_definition(parser & p, elaborator & elab, def_cmd_kind kind, expr const & fn, expr const & val, pos_info const & pos) {
    if (p.profiling()) {
        std::ostringstream msg;
        display_pos(msg, p, pos);
        msg << " elaboration time for " << local_pp_name(fn);
        timeit timer(p.ios().get_diagnostic_stream(), msg.str().c_str(), LEAN_PROFILE_THRESHOLD);
        return elaborate_definition_core(elab, kind, fn, val);
    } else {
        return elaborate_definition_core(elab, kind, fn, val);
    }
}

static void finalize_definition(elaborator & elab, buffer<expr> const & params, expr & type, expr & val, buffer<name> & lp_names) {
    type = elab.mk_pi(params, type);
    val  = elab.mk_lambda(params, val);
    buffer<expr> type_val;
    buffer<name> implicit_lp_names;
    type_val.push_back(type);
    type_val.push_back(val);
    elab.finalize(type_val, implicit_lp_names, true, false);
    type = type_val[0];
    val  = type_val[1];
    lp_names.append(implicit_lp_names);
}

static pair<environment, name> mk_real_name(environment const & env, name const & c_name, bool is_private, pos_info const & pos) {
    environment new_env = env;
    name c_real_name;
    if (is_private) {
        unsigned h  = hash(pos.first, pos.second);
        auto env_n  = add_private_name(new_env, c_name, optional<unsigned>(h));
        new_env     = env_n.first;
        c_real_name = env_n.second;
    } else {
        name const & ns = get_namespace(env);
        c_real_name     = ns + c_name;
    }
    return mk_pair(new_env, c_real_name);
}

static certified_declaration check(parser & p, environment const & env, name const & c_name, declaration const & d, pos_info const & pos) {
    if (p.profiling()) {
        std::ostringstream msg;
        display_pos(msg, p, pos);
        msg << " type checking time for " << c_name;
        timeit timer(p.ios().get_diagnostic_stream(), msg.str().c_str(), LEAN_PROFILE_THRESHOLD);
        return ::lean::check(env, d);
    } else {
        return ::lean::check(env, d);
    }
}

static void check_noncomputable(parser & p, environment const & env, name const & c_name, name const & c_real_name, bool is_noncomputable) {
    if (p.ignore_noncomputable())
        return;
    if (!is_noncomputable && is_marked_noncomputable(env, c_real_name)) {
        auto reason = get_noncomputable_reason(env, c_real_name);
        lean_assert(reason);
        if (p.in_theorem_queue(*reason)) {
            throw exception(sstream() << "definition '" << c_name << "' was marked as noncomputable because '" << *reason
                            << "' is still in theorem queue (solution: use command 'reveal " << *reason << "'");
        } else {
            throw exception(sstream() << "definition '" << c_name << "' is noncomputable, it depends on '" << *reason << "'");
        }
    }
    if (is_noncomputable && !is_marked_noncomputable(env, c_real_name)) {
        throw exception(sstream() << "definition '" << c_name << "' was incorrectly marked as noncomputable");
    }
}

static environment compile_decl(parser & p, environment const & env, def_cmd_kind kind, bool is_noncomputable,
                                name const & c_name, name const & c_real_name, pos_info const & pos) {
    if (is_noncomputable || kind == Theorem || is_vm_builtin_function(c_real_name))
        return env;
    try {
        declaration d = env.get(c_real_name);
        return vm_compile(env, d);
    } catch (exception & ex) {
        flycheck_warning wrn(p.ios());
        auto & out = p.ios().get_regular_stream();
        display_pos(out, p, pos);
        out << "failed to generate bytecode for '" << c_name << "'" << std::endl;
        type_context ctx(p.env());
        auto out2  = regular(p.env(), p.ios(), ctx);
        display_warning(out2, get_pos_info_provider(), ex);
        return env;
    }
}

static pair<environment, name>
declare_definition(parser & p, environment const & env, def_cmd_kind kind, buffer<name> const & lp_names,
                   name const & c_name, expr const & type, expr const & val,
                   bool is_private, bool is_protected, bool is_noncomputable,
                   decl_attributes attrs, pos_info const & pos) {
    auto env_n = mk_real_name(env, c_name, is_private, pos);
    environment new_env = env_n.first;
    name c_real_name    = env_n.second;

    bool use_conv_opt = true;
    bool is_trusted   = kind != MetaDefinition;
    auto def          = mk_definition(new_env, c_real_name, to_list(lp_names), type, val, use_conv_opt, is_trusted);
    auto cdef         = check(p, new_env, c_name, def, pos);
    new_env           = module::add(new_env, cdef);

    check_noncomputable(p, new_env, c_name, c_real_name, is_noncomputable);

    if (is_protected)
        new_env = add_protected(new_env, c_real_name);

    if (!is_private) {
        p.add_decl_index(c_real_name, pos, p.get_cmd_token(), type);
        new_env = ensure_decl_namespaces(new_env, c_real_name);
    }

    new_env = attrs.apply(new_env, p.ios(), c_real_name);
    new_env = compile_decl(p, new_env, kind, is_noncomputable, c_name, c_real_name, pos);
    return mk_pair(new_env, c_real_name);
}

environment xdefinition_cmd_core(parser & p, def_cmd_kind kind, bool is_private, bool is_protected, bool is_noncomputable,
                                 decl_attributes attrs) {
    buffer<name> lp_names;
    buffer<expr> params;
    expr fn, val;
    auto header_pos = p.pos();
    declaration_info_scope scope(p.env(), is_private, is_noncomputable, kind);
    std::tie(fn, val) = parse_definition(p, lp_names, params, kind == def_cmd_kind::Example);
    if (p.used_sorry()) p.declare_sorry();
    elaborator elab(p.env(), p.get_options(), metavar_context(), local_context());
    buffer<expr> new_params;
    elaborate_params(elab, params, new_params);
    elab.set_instance_fingerprint();
    replace_params(params, new_params, fn, val);
    expr type;
    std::tie(val, type) = elaborate_definition(p, elab, kind, fn, val, header_pos);
    // TODO(Leo): postprocess nested matches and equations
    finalize_definition(elab, new_params, type, val, lp_names);
    if (kind == Example) return p.env();
    name c_name = mlocal_name(fn);
    auto env_n  = declare_definition(p, elab.env(), kind, lp_names, c_name, type, val,
                                     is_private, is_protected, is_noncomputable, attrs, header_pos);
    environment new_env = env_n.first;
    name c_real_name    = env_n.second;
    return add_local_ref(p, new_env, c_name, c_real_name, lp_names, params);
}
}