#include <sys/stat.h>

#include <ostd/types.hh>
#include <ostd/string.hh>
#include <ostd/vector.hh>

#include <cubescript.hh>

/* represents a rule definition, possibly with a function */
struct Rule {
    ostd::String target;
    ostd::Vector<ostd::String> deps;
    ostd::Uint32 *func;

    Rule(): target(), deps(), func(nullptr) {}
    Rule(const Rule &r): target(r.target), deps(r.deps), func(r.func) {
        cscript::bcode_ref(func);
    }
    ~Rule() { cscript::bcode_unref(func); }
};

ostd::Vector<Rule> rules;

/* check funcs */

static bool ob_check_ts(ostd::ConstCharRange tname,
                        const ostd::Vector<ostd::String> &deps) {
    auto get_ts = [](ostd::ConstCharRange fname) -> time_t {
        struct stat st;
        if (stat(ostd::String(fname).data(), &st) < 0)
            return 0;
        return st.st_mtime;
    };
    time_t tts = get_ts(tname.data());
    if (!tts) return true;
    for (auto &dep: deps.iter()) {
        time_t sts = get_ts(dep.data());
        if (sts && tts < sts) return true;
    }
    return false;
}

static bool ob_check_file(ostd::ConstCharRange fname) {
    return ostd::FileStream(fname, ostd::StreamMode::read).is_open();
}

static bool ob_check_exec(ostd::ConstCharRange tname,
                          const ostd::Vector<ostd::String> &deps) {
    if (!ob_check_file(tname))
        return true;
    for (auto &dep: deps.iter())
        if (!ob_check_file(dep))
            return true;
    return ob_check_ts(tname, deps);
}

/* this lets us properly match % patterns in target names */
static ostd::ConstCharRange ob_compare_subst(ostd::ConstCharRange expanded,
                                             ostd::ConstCharRange toexpand) {
    auto rep = ostd::find(toexpand, '%');
    /* no subst found */
    if (rep.empty())
        return nullptr;
    /* get the part before % */
    auto fp = ostd::slice_until(toexpand, rep);
    /* part before % does not compare, so ignore */
    if (expanded.size() <= fp.size())
        return nullptr;
    if (expanded.slice(0, fp.size()) != fp)
        return nullptr;
    /* pop out front part */
    expanded.pop_front_n(fp.size());
    /* part after % */
    rep.pop_front();
    if (rep.empty())
        return expanded;
    /* part after % does not compare, so ignore */
    if (expanded.size() <= rep.size())
        return nullptr;
    if (expanded.slice(expanded.size() - rep.size(), expanded.size()) != rep)
        return nullptr;
    /* cut off latter part */
    expanded.pop_back_n(rep.size());
    /* we got what we wanted... */
    return expanded;
}

struct ObState {
    cscript::CsState cs;
    ostd::ConstCharRange progname;

    struct SubRule {
        ostd::ConstCharRange sub;
        Rule *rule;
    };

    template<typename ...A>
    int error(int retcode, ostd::ConstCharRange fmt, A &&...args) {
        ostd::err.write(progname, ": ");
        ostd::err.writefln(fmt, ostd::forward<A>(args)...);
        return retcode;
    }

    int exec_list(const ostd::Vector<SubRule> &rlist,
                  ostd::Vector<ostd::String> &subdeps,
                  ostd::ConstCharRange tname) {
        ostd::String repd;
        for (auto &sr: rlist.iter()) for (auto &target: sr.rule->deps.iter()) {
            ostd::ConstCharRange atgt = target.iter();
            repd.clear();
            auto lp = ostd::find(atgt, '%');
            if (!lp.empty()) {
                repd.append(ostd::slice_until(atgt, lp));
                repd.append(sr.sub);
                lp.pop_front();
                if (!lp.empty()) repd.append(lp);
                atgt = repd.iter();
            }
            subdeps.push(atgt);
            int r = exec_rule(atgt, tname);
            if (r) return r;
        }
        return 0;
    }

    int exec_func(ostd::ConstCharRange tname,
                  const ostd::Vector<SubRule> &rlist) {
        ostd::Vector<ostd::String> subdeps;
        int r = exec_list(rlist, subdeps, tname);
        if (ob_check_exec(tname, subdeps)) {
            if (r) return r;
            ostd::Uint32 *func = nullptr;
            for (auto &sr: rlist.iter()) {
                Rule &r = *sr.rule;
                if (!r.func)
                    continue;
                if (func)
                    return error(1, "redefinition of rule '%s'", tname);
                func = r.func;
            }
            if (func) {
                cscript::StackedValue targetv, sourcev, sourcesv;

                targetv.id = cs.new_ident("target");
                if (!cscript::check_alias(targetv.id))
                    return 1;
                targetv.set_cstr(tname);
                targetv.push();

                if (subdeps.size() > 0) {
                    sourcev.id = cs.new_ident("source");
                    sourcesv.id = cs.new_ident("sources");
                    if (!cscript::check_alias(sourcev.id))
                        return 1;
                    if (!cscript::check_alias(sourcesv.id))
                        return 1;

                    sourcev.set_cstr(subdeps[0]);
                    sourcev.push();

                    auto dsv = ostd::appender<ostd::String>();
                    ostd::concat(dsv, subdeps);
                    ostd::Size len = dsv.size();
                    sourcesv.set_str(ostd::CharRange(dsv.get().disown(), len));
                    sourcesv.push();
                }

                return cs.run_int(func);
            }
        }
        return 0;
    }

    int exec_rule(ostd::ConstCharRange target,
                  ostd::ConstCharRange from = nullptr) {
        ostd::Vector<SubRule> rlist;
        for (auto &rule: rules.iter()) {
            if (target == rule.target) {
                rlist.push().rule = &rule;
                continue;
            }
            ostd::ConstCharRange sub = ob_compare_subst(target, rule.target);
            if (!sub.empty()) {
                SubRule &sr = rlist.push();
                sr.rule = &rule;
                sr.sub = sub;
            }
        }
        if (rlist.empty() && !ob_check_file(target)) {
            if (from.empty())
                return error(1, "no rule to run target '%s'", target);
            else
                return error(1, "no rule to run target '%s' (needed by '%s')",
                             target, from);
            return 1;
        }
        return exec_func(target, rlist);
    }
};

int main(int argc, char **argv) {
    ObState os;
    ostd::ConstCharRange pn = argv[0];
    ostd::ConstCharRange lslash = ostd::find_last(pn, '/');
    if (!lslash.empty()) {
        lslash.pop_front();
        os.progname = lslash;
    } else
        os.progname = pn;

    cscript::init_lib_base(os.cs);
    cscript::init_lib_io(os.cs);
    cscript::init_lib_math(os.cs);
    cscript::init_lib_string(os.cs);
    cscript::init_lib_list(os.cs);

    os.cs.add_command("shell", "C", [](cscript::CsState &cs, char *s) {
        cs.result->set_int(system(s));
    });

    os.cs.add_command("rule", "sseN", [](cscript::CsState &, const char *tgt,
                                         const char *dep, ostd::Uint32 *body,
                                         int *numargs) {
        ostd::Vector<ostd::String> targets = cscript::util::list_explode(tgt);
        ostd::Vector<ostd::String> deps = cscript::util::list_explode(dep);
        for (auto &target: targets.iter()) {
            Rule &r = rules.push();
            r.target = target;
            if (*numargs > 2) {
                r.func = body;
                cscript::bcode_ref(body);
            }
            for (auto &dep: deps.iter())
                r.deps.push(dep);
        }
    });

    if (!os.cs.run_file("cubefile", true))
        return os.error(1, "failed creating rules");

    if (rules.empty())
        return os.error(1, "no targets");

    return os.exec_rule((argc > 1) ? argv[1] : "all");
}