#include "web.h"
#include "db.h"
#include <algorithm>
#include <chrono>
#include <leveldb/comparator.h>

static const leveldb::Comparator *cmp = leveldb::BytewiseComparator();

static inline uint64_t now() {
    return std::chrono::duration_cast<std::chrono::milliseconds>(
        std::chrono::high_resolution_clock::now().time_since_epoch()).count();
}

// uint64_t is long
inline void strToL(unsigned long int *l, std::string s) {
	*l = std::stoul(s);
}
// uint64_t is long long
inline void strToL(unsigned long long int *l, std::string s) {
	*l = std::stoull(s);
}

static inline void reply_header(struct mg_connection *conn, const bool ok, const char *msg, const char *extra = "") {
    mg_printf(conn,
            "HTTP/1.1 %s %s\r\n"
            "%s",
            (ok) ? "200" : "500",
            msg,
            extra);
}

static inline bool parse_key(leveldb::Slice &&key, uint64_t *value) {
    if (key.size() != 20+3) 
        return false;
    strToL(value, key.data()+3);
    return true;
}

const boost::regex web_handle_api_value_R(
    "/api/value/([a-zA-Z0-9_\\.]+)");
void web_handle_api_value(const boost::cmatch &match, struct mg_connection *conn) {
    std::string sensor(match[1].str());
    uint64_t timestamp = now();
    char buf[1024];
    int bytesRead = mg_read(conn, buf, 1024);
    std::string value(buf, bytesRead);

    if (db_insert(sensor, timestamp, value)) {
        reply_header(conn, true, "OK Value received", "\r\n");
    } else {
        reply_header(conn, false, "Internal Error", "\r\n");
    }
}

const boost::regex web_handle_api_value_timestamp_R(
    "/api/value/([a-zA-Z0-9_\\.]+)/([0-9]+)");
void web_handle_api_value_timestamp(const boost::cmatch &match, struct mg_connection *conn) {
    std::string sensor(match[1].str());
    uint64_t timestamp; strToL(&timestamp, match[2].str());
    char buf[1024];
    int bytesRead = mg_read(conn, buf, 1024);
    std::string value(buf, bytesRead);

    if (db_insert(sensor, timestamp, value)) {
        reply_header(conn, true, "OK Value received", "\r\n");
    } else {
        reply_header(conn, false, "Internal Error", "\r\n");
    }
}

static inline void print_json_tuple(struct mg_connection *conn,
        std::ostringstream &outbuf,
        leveldb::Slice &&key,
        leveldb::Slice &&value) {

    size_t key_size =  key.size();
    if (key_size != 20+3) {
        std::cerr << "invalid key" << std::endl;
        return;
    }

    unsigned int offset = 3; // "ts-"
    // skip zeros in timestamp
    while (offset < key_size-1 and *(key.data()+offset) == '0')
        offset++;

    outbuf << '[';
    outbuf.write(key.data()+offset, key_size-offset);
    outbuf << ',';
    outbuf.write(value.data(), value.size());
    outbuf << ']';

    mg_write(conn, outbuf.str().c_str(), outbuf.tellp());
}


const boost::regex web_handle_api_range_R(
    "/api/range/([a-zA-Z0-9_\\.]+)/([0-9]+)/([0-9]+)");
void web_handle_api_range(const boost::cmatch &match, struct mg_connection *conn) {
    std::string sensor(match[1].str());
    uint64_t start; strToL(&start, match[2].str());
    uint64_t end; strToL(&end, match[3].str());
    std::string key_start(std::move(db_make_key(start)));
    std::string key_end(std::move(db_make_key(end)));

    leveldb::DB *db = db_get(sensor);
    if (db == nullptr) {
        reply_header(conn, false, "Internal Error", "\r\n");
        return;
    }

    reply_header(conn, true, "OK", "Content-Type: application/json\r\n\r\n");

    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()) {
        if (first) first = false;
        else outbuf << ",";
        print_json_tuple(conn, outbuf, it->key(), it->value());
        outbuf.seekp(0);
    }
    mg_printf(conn, "]}\r\n");
    delete it;
}

const boost::regex web_handle_api_range_size_R(
    "/api/range/([a-zA-Z0-9_\\.]+)/([0-9]+)/([0-9]+)/([0-9]+)");
void web_handle_api_range_size(const boost::cmatch &match, struct mg_connection *conn) {
    std::string sensor(match[1].str());
    uint64_t start; strToL(&start, match[2].str());
    uint64_t end; strToL(&end, match[3].str());
    uint64_t size; strToL(&size, match[4].str());

    leveldb::DB *db = db_get(sensor);
    if (db == nullptr) {
        reply_header(conn, false, "Internal Error", "\r\n");
        return;
    }

    reply_header(conn, true, "OK", "Content-Type: application/json\r\n\r\n");

    uint64_t step = std::max((uint64_t)1, (end-start) / size);

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

    bool first = true;
    uint64_t actual_size = 0;
    std::ostringstream outbuf;
    leveldb::Iterator* it = db->NewIterator(leveldb::ReadOptions());
    for (uint64_t key = start; key < end; key += step) {
        it->Seek(db_make_key(key));
        if (!it->Valid()) continue;

        if (first) first = false;
        else outbuf << ",";

        print_json_tuple(conn, outbuf, it->key(), it->value());
        outbuf.seekp(0);
        actual_size++;
    }
    outbuf << "], \"actual_size\":" << actual_size << "}\r\n";
    mg_write(conn, outbuf.str().c_str(), outbuf.tellp());
    delete it;
}