extern "C" {
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <magic.h>
#include "mongoose.h"
}

#include <algorithm>
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <map>
#include <forward_list>
#include <functional>
#include <mutex>

#include <boost/regex.hpp>

#include "leveldb/db.h"
#include "leveldb/comparator.h"

std::forward_list<std::pair<boost::regex,std::function<void(const boost::cmatch&, struct mg_connection *conn)>>> web_handler;

static std::map<std::string,leveldb::DB*> dbs;

static magic_t magic_cookie;

struct mg_context *ctx;

bool sensor_name_is_sane(std::string& name) {
    for (auto it = name.begin(); it != name.end(); ++it) {
        if (not (*it >= '0' and *it <= '9' or
                 *it >= 'A' and *it <= 'Z' or
                 *it >= 'a' and *it <= 'z')) {
            return false;
        }
    }
    return true;
}

std::mutex getDBmutex;

leveldb::DB *getDB(std::string& name) {
    getDBmutex.lock();
    if (dbs.find(name) == dbs.end()) {
        if (not sensor_name_is_sane(name)) {
            getDBmutex.unlock();
            return nullptr;
        }
        leveldb::DB *db;
        leveldb::Options options;
        options.create_if_missing = true;
        leveldb::Status status = leveldb::DB::Open(options, "/tmp/testdb."+name, &db);
        if (not status.ok()) {
            std::cout << status.ToString() << std::endl;
            getDBmutex.unlock();
            return nullptr;
        }
        dbs[name] = db;
        getDBmutex.unlock();
        return db;
    } else {
        getDBmutex.unlock();
        return dbs.at(name);
    }
}

// see http_parser.h
// char DELETE = 0;
// char GET = 1;
// char HEAD = 2;
// char POST = 3;
// char PUT = 4;


static inline void http_ok(int fd, const char *content_type, const char *extra_headers) {
#define write_const(fd, text) \
    write(fd, text, strlen(text));
 
    write_const(fd, "HTTP/1.1 200 OK\r\nContent-Type: ");
    write_const(fd, content_type);
    write_const(fd, "\r\n");
    if (extra_headers) write_const(fd, extra_headers);
    write_const(fd, "\r\n");
#undef write_const
}

std::string make_key(uint64_t timestamp) {
    std::stringstream key;
    key << "ts-";
    key << std::setfill('0') << std::setw(20) << timestamp;
    return key.str();
}

void web_handle_api_value(const boost::cmatch &match, struct mg_connection *conn) {
    const struct mg_request_info *request_info = mg_get_request_info(conn);

    std::string sensor(match[1].str());
    uint64_t timestamp = std::stoul(match[2].str());
    char buf[1024];
    int count = mg_read(conn, buf, 1024);
    std::string value(buf, count);

    leveldb::DB *db = getDB(sensor);
    if (db == nullptr) {
        std::cout << "failed to get db for " << sensor << std::endl;
        mg_printf(conn, "HTTP/1.1 500 Internal Error\r\n\r\n");
        return;
    }

    std::cout << "sensor=" << sensor << " key=" << make_key(timestamp) << std::endl;
    db->Put(leveldb::WriteOptions(), make_key(timestamp), value);
    mg_printf(conn, "HTTP/1.1 200 Value received\r\n\r\n");
}

void web_handle_api_range(const boost::cmatch &match, struct mg_connection *conn) {
    static const leveldb::Comparator *cmp = leveldb::BytewiseComparator();

    std::string sensor(match[1].str());
    uint64_t start = std::stoul(match[2].str());
    uint64_t end = std::stoul(match[3].str());
    std::string key_start(std::move(make_key(start)));
    std::string key_end(std::move(make_key(end)));

    leveldb::DB *db = getDB(sensor);
    if (db == nullptr) {
        mg_printf(conn, "HTTP/1.1 500 Internal Error\r\n\r\n");
        return;
    }
        
    mg_printf(conn,
              "HTTP/1.1 200 Value received\r\n"
              "Content-Type: application/json; encoding=UTF-8\r\n"
              "\r\n");

    std::cout << "sensor=" << sensor << " start=" << start << " end=" << end << std::endl;

    std::ostringstream out;
    out << "{'sensor':'" << sensor << "', 'error':null, 'data':[";
    mg_write(conn, out.str().c_str(), out.str().size());

    leveldb::Iterator* it = db->NewIterator(leveldb::ReadOptions());
    bool first = true;
    std::ostringstream outbuf;
    for (it->Seek(key_start); 
                 it->Valid() && cmp->Compare(it->key(), key_end) < 0;
                 it->Next()) {
            const char *key = it->key().data();
            size_t key_size =  it->key().size();
            if (key_size != 20+3) {
                std::cerr << "invalid key" << std::endl;
                return;
            }

            int offset = 3; //ts-
            // skip zeros in timestamp
            while (offset < key_size-1 and *(key+offset) == '0')
                offset++;
            
            if (first)
                first = false;
            else
                outbuf << ',';
            
            outbuf << '[';
            outbuf.write(key+offset, key_size-offset);
            outbuf << ',';
            outbuf.write(it->value().data(), it->value().size());
            outbuf << ']';

            mg_write(conn, outbuf.str().c_str(), outbuf.tellp());
            outbuf.seekp(0);
    }
    mg_printf(conn, "]}\r\n");
    delete it;
}

int begin_request_handler(struct mg_connection *conn) {
    boost::cmatch match;

    const char *url = mg_get_request_info(conn)->uri;

    for (auto item = web_handler.begin(); item != web_handler.end(); ++item) {
        if (boost::regex_match(url, match, (*item).first)) {
            (*item).second(match, conn);
            return 1;
        }
    }
    
    return 0;
}


void sigint_handler(int s) {
    // Stop the server.
    mg_stop(ctx);

    // Close databases
    for (auto it = dbs.begin(); it != dbs.end(); ++it) {
        std::cout << "Close " << (*it).first << std::endl;
        delete (*it).second;
        dbs.erase(it);
    }

    exit(0);
}


int main(int argc, char **argv) {
    struct mg_callbacks callbacks;
    const char *options[] = {
        "listening_ports", "8080",
        "document_root", "wwwroot",
        NULL};

    memset(&callbacks, 0, sizeof(callbacks));
    callbacks.begin_request = begin_request_handler;


    // Routing
    web_handler.push_front(std::make_pair(
                boost::regex("/api/value/([a-zA-Z0-9]+)/([0-9]+)"),
                web_handle_api_value));
    web_handler.push_front(std::make_pair(
                boost::regex("/api/range/([a-zA-Z0-9]+)/([0-9]+)/([0-9]+)"),
                web_handle_api_range));

    magic_cookie = magic_open(MAGIC_MIME_TYPE);
    magic_load(magic_cookie, NULL);


    // Signals: handle C-c
    struct sigaction on_sigint;
    on_sigint.sa_handler = sigint_handler;
    sigemptyset(&on_sigint.sa_mask);
    on_sigint.sa_flags = 0;
    
    sigaction(SIGINT, &on_sigint, NULL);


    // Start the web server.
    ctx = mg_start(&callbacks, NULL, options);

    while (1) sleep(1);
    return 1;
}