#include <sys/stat.h>
#include <dirent.h>
#include <unistd.h>

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

#include <cubescript.hh>

#include "tpool.hh"

using ostd::ConstCharRange;
using ostd::Vector;
using ostd::String;
using ostd::Uint32;
using ostd::slice_until;

/* represents a rule definition, possibly with a function */
struct Rule {
    String target;
    Vector<String> deps;
    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); }
};

Vector<Rule> rules;

struct RuleCounter;
Vector<RuleCounter *> counters;

struct RuleCounter {
    RuleCounter(): cond(), mtx(), counter(0), result(0) {
        counters.push(this);
    }

    void wait() {
        mtx.lock();
        while (counter)
            cond.wait(mtx);
        mtx.unlock();
    }

    void incr() {
        mtx.lock();
        ++counter;
        mtx.unlock();
    }

    void decr() {
        mtx.lock();
        if (!--counter) {
            mtx.unlock();
            cond.broadcast();
        } else
            mtx.unlock();
    }

    int wait_result(int ret) {
        counters.pop();
        if (ret)
            return ret;
        wait();
        ret = result;
        if (ret)
            return ret;
        return 0;
    }

    Cond cond;
    Mutex mtx;
    volatile int counter;
    ostd::AtomicInt result;
};

ThreadPool tpool;

/* check funcs */

static bool ob_check_ts(ConstCharRange tname, const Vector<String> &deps) {
    auto get_ts = [](ConstCharRange fname) -> time_t {
        struct stat st;
        if (stat(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(ConstCharRange fname) {
    return ostd::FileStream(fname, ostd::StreamMode::read).is_open();
}

static bool ob_check_exec(ConstCharRange tname, const Vector<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 ConstCharRange ob_compare_subst(ConstCharRange expanded,
                                       ConstCharRange toexpand) {
    auto rep = ostd::find(toexpand, '%');
    /* no subst found */
    if (rep.empty())
        return nullptr;
    /* get the part before % */
    auto fp = 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;
}

/* expand globs */
static void ob_get_path_parts(Vector<ConstCharRange> &parts,
                              ConstCharRange elem) {
    ConstCharRange star = ostd::find(elem, '*');
    while (!star.empty()) {
        ConstCharRange ep = slice_until(elem, star);
        if (!ep.empty())
            parts.push(ep);
        parts.push("*");
        elem = star;
        elem.pop_front();
        star = ostd::find(elem, '*');
    }
    if (!elem.empty())
        parts.push(elem);
}

static bool ob_path_matches(ConstCharRange fn,
                            const Vector<ConstCharRange> &parts) {
    auto it = parts.iter();
    while (!it.empty()) {
        ConstCharRange elem = it.front();
        if (elem == "*") {
            it.pop_front();
            /* skip multiple stars if present */
            while (!it.empty() && ((elem = it.front()) == "*"))
                it.pop_front();
            /* trailing stars, we match */
            if (it.empty())
                return true;
            /* skip about as much as we can until the elem part matches */
            while (fn.size() > elem.size()) {
                if (fn.slice(0, elem.size()) == elem)
                    break;
                fn.pop_front();
            }
        }
        /* non-star here */
        if (fn.size() < elem.size())
            return false;
        if (fn.slice(0, elem.size()) != elem)
            return false;
        fn.pop_front_n(elem.size());
        /* try next element */
        it.pop_front();
    }
    /* if there are no chars in the fname remaining, we fully matched */
    return fn.empty();
}

static bool ob_expand_glob(String &ret, ConstCharRange src, bool ne = false);

static bool ob_expand_dir(String &ret, ConstCharRange dir,
                          const Vector<ConstCharRange> &parts,
                          ConstCharRange slash) {
    DIR *d = opendir(String(dir).data());
    bool appended = false;
    if (!d)
        return false;
    struct dirent *dirp;
    while ((dirp = readdir(d))) {
        ConstCharRange fn = (const char *)dirp->d_name;
        if (fn.empty() || (fn == ".") || (fn == ".."))
            continue;
        /* check if filename matches */
        if (!ob_path_matches(fn, parts))
            continue;
        String afn((dir == ".") ? "" : "./");
        afn.append(fn);
        /* if we reach this, we match; try recursively matching */
        if (!slash.empty()) {
            afn.append(slash);
            ConstCharRange psl = slash;
            psl.pop_front();
            if (!ostd::find(psl, '*').empty()) {
                if (!appended)
                    appended = ob_expand_glob(ret, afn.iter());
                continue;
            }
            /* no further star, just do file test */
            if (!ob_check_file(afn.iter()))
                continue;
            if (!ret.empty())
                ret.push(' ');
            ret.append(afn);
            appended = true;
            continue;
        }
        if (!ret.empty())
            ret.push(' ');
        ret.append(afn);
        appended = true;
    }
    closedir(d);
    return appended;
}

static bool ob_expand_glob(String &ret, ConstCharRange src, bool ne) {
    ConstCharRange star = ostd::find(src, '*');
    /* no star use as-is */
    if (star.empty()) {
        if (ne) return false;
        if (!ret.empty())
            ret.push(' ');
        ret.append(src);
        return false;
    }
    /* part before star */
    ConstCharRange prestar = slice_until(src, star);
    /* try finding slash before star */
    ConstCharRange slash = ostd::find_last(prestar, '/');
    /* directory to scan */
    ConstCharRange dir = ".";
    /* part of name before star */
    ConstCharRange fnpre = prestar;
    if (!slash.empty()) {
        /* there was slash, adjust directory + prefix accordingly */
        dir = slice_until(src, slash);
        fnpre = slash;
        fnpre.pop_front();
    }
    /* part after star */
    ConstCharRange fnpost = star;
    fnpost.pop_front();
    /* if a slash follows, adjust */
    ConstCharRange nslash = ostd::find(fnpost, '/');
    if (!nslash.empty())
        fnpost = slice_until(fnpost, nslash);
    /* retrieve the single element with whatever stars in it, chop it up */
    Vector<ConstCharRange> parts;
    ob_get_path_parts(parts, ConstCharRange(&fnpre[0], &fnpost[fnpost.size()]));
    /* do a directory scan and match */
    if (!ob_expand_dir(ret, dir, parts, nslash)) {
        if (ne) return false;
        if (!ret.empty())
            ret.push(' ');
        ret.append(src);
        return false;
    }
    return true;
}

static String ob_expand_globs(const Vector<String> &src) {
    String ret;
    for (auto &s: src.iter())
        ob_expand_glob(ret, s.iter());
    return ret;
}

struct ObState {
    cscript::CsState cs;
    ConstCharRange progname;
    int jobs = 1;

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

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

    int exec_list(const Vector<SubRule> &rlist, Vector<String> &subdeps,
                  ConstCharRange tname) {
        String repd;
        for (auto &sr: rlist.iter()) for (auto &target: sr.rule->deps.iter()) {
            ConstCharRange atgt = target.iter();
            repd.clear();
            auto lp = ostd::find(atgt, '%');
            if (!lp.empty()) {
                repd.append(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(ConstCharRange tname, const Vector<SubRule> &rlist) {
        Vector<String> subdeps;
        /* new scope for early destruction */
        {
            RuleCounter depcnt;
            int r = depcnt.wait_result(exec_list(rlist, subdeps, tname));
            if (r)
                return r;
        }
        if (ob_check_exec(tname, subdeps)) {
            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<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(ConstCharRange target, ConstCharRange from = nullptr) {
        Vector<SubRule> rlist;
        for (auto &rule: rules.iter()) {
            if (target == rule.target) {
                rlist.push().rule = &rule;
                continue;
            }
            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);
    }
};

static int ob_print_help(ConstCharRange a0, ostd::Stream &os, int v) {
    os.writeln("Usage: ", a0,  " [options] [target]\n",
               "Options:\n"
               "  -C DIRECTORY\tChange to DIRECTORY before running.\n",
               "  -f FILE\tSpecify the file to run (default: cubefile).\n"
               "  -h\t\tPrint this message.\n"
               "  -j N\t\tSpecify the number of jobs to use (default: 1).");
    return v;
}

int main(int argc, char **argv) {
    ObState os;
    ConstCharRange pn = argv[0];
    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);

    ConstCharRange fname = "cubefile";

    int ac;
    while ((ac = getopt(argc, argv, "C:f:hj:")) >= 0) {
        switch (ac) {
        case 'C':
            if (chdir(optarg) < 0)
                return os.error(1, "failed changing directory: %s", optarg);
            break;
        case 'f':
            fname = optarg;
            break;
        case 'h':
            return ob_print_help(argv[0], ostd::out, 0);
        case 'j':
            os.jobs = ostd::max(1, atoi(optarg));
            break;
        default:
            return ob_print_help(argv[0], ostd::err, 1);
            break;
        }
    }

    tpool.init(os.jobs);

    os.cs.add_command("shell", "C", [](cscript::CsState &cs, ConstCharRange s) {
        RuleCounter *cnt = counters.back();
        cnt->incr();
        char *ds = String(s).disown();
        tpool.push([cnt, ds]() {
            int ret = system(ds);
            delete[] ds;
            if (ret && !cnt->result)
                cnt->result = ret;
            cnt->decr();
        });
        cs.result->set_int(0);
    });

    os.cs.add_command("rule", "sseN", [](cscript::CsState &, const char *tgt,
                                         const char *dep, ostd::Uint32 *body,
                                         int *numargs) {
        auto targets = cscript::util::list_explode(tgt);
        auto 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);
        }
    });

    os.cs.add_command("glob", "C", [](cscript::CsState &cs, ConstCharRange lst) {
        auto fnames = cscript::util::list_explode(lst);
        cs.result->set_str(ob_expand_globs(fnames).disown());
    });

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

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

    RuleCounter maincnt;
    int ret = os.exec_rule((optind < argc) ? argv[optind] : "all");
    ret = maincnt.wait_result(ret);
    if (ret)
        return ret;
    tpool.destroy();
    return 0;
}