/*
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 "kernel/replace_fn.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/unfold_macros.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/replace_visitor.h"
#include "library/equations_compiler/equations.h"
#include "library/compiler/vm_compiler.h"
#include "library/compiler/rec_fn_macro.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"
#include "frontends/lean/update_environment_exception.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_period_tk())) {
            auto period_pos = p.pos();
            p.next();
            eqns.push_back(p.save_pos(mk_no_equation(), period_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, decl_modifiers const & modifiers, decl_attributes /* attrs */) {
    buffer<name> lp_names;
    buffer<expr> fns, params;
    declaration_info_scope scope(p, kind, modifiers);
    expr val = parse_mutual_definition(p, lp_names, fns, params);
    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, bool is_instance) {
    parser::local_scope scope1(p);
    auto header_pos = p.pos();
    expr fn = parse_single_header(p, lp_names, params, is_example, is_instance);
    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_period_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_period_tk())) {
            auto period_pos = p.pos();
            p.next();
            eqns.push_back(p.save_pos(mk_no_equation(), period_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 = unfold_untrusted_macros(elab.env(), type_val[0]);
    val  = unfold_untrusted_macros(elab.env(), 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);
        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) {
        if (p.found_errors())
            return env;
        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 expr fix_rec_fn_name(expr const & e, name const & c_name, name const & c_real_name) {
    return replace(e, [&](expr const & m, unsigned) {
            if (is_rec_fn_macro(m) && get_rec_fn_name(m) == c_name) {
                return some_expr(mk_rec_fn_macro(c_real_name, get_rec_fn_type(m)));
            }
            return none_expr();
        });
}

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,
                   decl_modifiers const & modifiers, decl_attributes attrs, pos_info const & pos) {
    auto env_n = mk_real_name(env, c_name, modifiers.m_is_private, pos);
    environment new_env = env_n.first;
    name c_real_name    = env_n.second;
    expr val            = _val;
    if (modifiers.m_is_meta)
        val = fix_rec_fn_name(val, c_name, c_real_name);
    bool use_conv_opt = true;
    bool is_trusted   = !modifiers.m_is_meta;
    auto def          = kind == Theorem ?
        mk_theorem(c_real_name, to_list(lp_names), type, val) :
        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, modifiers.m_is_noncomputable);

    if (kind == Example)
        return mk_pair(env, c_real_name);

    if (modifiers.m_is_protected)
        new_env = add_protected(new_env, c_real_name);

    new_env = add_alias(new_env, modifiers.m_is_protected, c_name, c_real_name);

    if (!modifiers.m_is_private) {
        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, modifiers.m_is_noncomputable, c_name, c_real_name, pos);
    return mk_pair(new_env, c_real_name);
}

struct fix_rec_fn_macro_args_fn : public replace_visitor {
    buffer<expr> const &             m_params;
    buffer<pair<name, expr>> const & m_fns;

    fix_rec_fn_macro_args_fn(buffer<expr> const & params, buffer<pair<name, expr>> const & fns):
        m_params(params), m_fns(fns) {
    }

    expr fix_rec_fn_macro(name const & fn, expr const & type) {
        return mk_app(mk_rec_fn_macro(fn, type), m_params);
    }

    virtual expr visit_macro(expr const & e) override {
        if (is_rec_fn_macro(e)) {
            name n = get_rec_fn_name(e);
            for (unsigned i = 0; i < m_fns.size(); i++) {
                if (n == m_fns[i].first)
                    return fix_rec_fn_macro(m_fns[i].first, m_fns[i].second);
            }
        }
        return replace_visitor::visit_macro(e);
    }
};

static expr fix_rec_fn_macro_args(elaborator & elab, name const & fn, buffer<expr> const & params, expr const & type, expr const & val) {
    expr fn_new_type = elab.mk_pi(params, type);
    buffer<pair<name, expr>> fns;
    fns.emplace_back(fn, fn_new_type);
    return fix_rec_fn_macro_args_fn(params, fns)(val);
}

environment single_definition_cmd_core(parser & p, def_cmd_kind kind, decl_modifiers modifiers, decl_attributes attrs) {
    buffer<name> lp_names;
    buffer<expr> params;
    expr fn, val;
    auto header_pos = p.pos();
    declaration_info_scope scope(p, kind, modifiers);
    bool is_example  = (kind == def_cmd_kind::Example);
    bool is_instance = modifiers.m_is_instance;
    if (is_instance)
        attrs.set_attribute(p.env(), "instance");
    std::tie(fn, val) = parse_definition(p, lp_names, params, is_example, is_instance);
    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);

    auto process = [&](expr val) -> environment {
        expr type;
        std::tie(val, type) = elaborate_definition(p, elab, kind, fn, val, header_pos);
        if (modifiers.m_is_meta) {
            val = fix_rec_fn_macro_args(elab, mlocal_name(fn), new_params, type, val);
        }
        if (is_equations_result(val)) {
            // TODO(Leo): generate equation lemmas and induction principle
            lean_assert(is_equations_result(val));
            lean_assert(get_equations_result_size(val) == 1);
            val = get_equations_result(val, 0);
        }
        finalize_definition(elab, new_params, type, val, lp_names);
        name c_name = mlocal_name(fn);
        auto env_n  = declare_definition(p, elab.env(), kind, lp_names, c_name, type, val, modifiers, attrs, header_pos);
        if (kind == Example) return p.env();
        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);
    };

    try {
        return process(val);
    } catch (throwable & ex1) {
        if (kind == Example) throw;
        /* Try again using 'sorry' */
        expr sorry = p.mk_sorry(header_pos);
        modifiers.m_is_noncomputable = true;
        environment new_env;
        try {
            new_env = process(sorry);
        } catch (throwable & ex2) {
            /* Throw original error */
            ex1.rethrow();
        }
        std::shared_ptr<throwable> ex_ptr(ex1.clone());
        throw update_environment_exception(new_env, ex_ptr);
    }
}

environment definition_cmd_core(parser & p, def_cmd_kind kind, decl_modifiers const & modifiers, decl_attributes attrs) {
    if (modifiers.m_is_mutual)
        return mutual_definition_cmd_core(p, kind, modifiers, attrs);
    else
        return single_definition_cmd_core(p, kind, modifiers, attrs);
}
}