#include <cstdlib>
#include <iostream>
#include <stdio.h>
#include <fstream>
#include <vector>
#include <unistd.h>
using namespace std;

#include "bgzf.h"
#include "grabix.h"

int usage()
{
    cout << "usage: grabix index bgzf_file " << endl;
    cout << "       grabix grab bgzf_file line_start [line_end] " << endl;
    cout << endl;
    cout << "examples:" << endl;
    cout << "       # create a grabix index (big.vcf.gz.gbi)" << endl;
    cout << "       grabix index big.vcf.gz" << endl;
    cout << endl;
    cout << "       # extract the 100th line." << endl;
    cout << "       grabix grab big.vcf.gz 100 [line_end] " << endl;
    cout << endl;
    cout << "       # extract the 100th through the 200th lines." << endl;
    cout << "       grabix grab big.vcf.gz 100 200 " << endl;
    cout << endl;
    cout << "       # extract the 100 random lines." << endl;
    cout << "       grabix random big.vcf.gz 100" << endl;
    cout << endl;
    cout << "       # Is the file bgzipped?" << endl;
    cout << "       grabix check big.vcf.gz" << endl;
    cout << endl;
    cout << "       # get total number of lines in the file (minus the header)." << endl;
    cout << "       grabix size big.vcf.gz" << endl;
    cout << "version: " << VERSION << "\n";
    cout << endl;
    return EXIT_SUCCESS;
}


bool bgzf_getline_counting(BGZF * stream)
{
    int c = -1;
    while (true)
    {
        c = bgzf_getc (stream);
        if (c == -1)
            return true;
        else if (c == 10) // \n
            return false;
    }
}

/*
Create a gbi index for the file to facilitate
random access via the BGZF seek utility
*/
int create_grabix_index(string bgzf_file)
{
    if (!bgzf_is_bgzf(bgzf_file.c_str()))
    {
        cerr << "[grabix] " << bgzf_file << " doesn't exist or wasn't compressed with bgzip" << endl;
        exit (1);
    }

    BGZF *bgzf_fp = bgzf_open(bgzf_file.c_str(), "r");
    if (bgzf_fp == NULL)
    {
        cerr << "[grabix] could not open file: " << bgzf_file << endl;
        exit (1);
    }

    // create an index for writing
    string index_file_name = bgzf_file + ".gbi.tmp";
    ofstream index_file(index_file_name.c_str(), ios::out);

    // add the offset for the end of the header to the index

    int status;
    kstring_t *line = new kstring_t;
    line->s = '\0';
    line->l = 0;
    line->m = 0;

    int64_t prev_offset = 0;
    int64_t offset = 0;
    while ((status = bgzf_getline(bgzf_fp, '\n', line)) >= 0)
    {
        offset = bgzf_tell (bgzf_fp);
        if (line->s[0] != '#')
            break;
        prev_offset = offset;
    }
    index_file << prev_offset << endl;

    // add the offsets for each CHUNK_SIZE
    // set of records to the index
    size_t chunk_count = 0;
    int64_t total_lines = 1;
    vector<int64_t> chunk_positions;
    chunk_positions.push_back (prev_offset);
    int eof = 1;
    while (true)
    {
        // grab the next line and store the offset
        eof = bgzf_getline(bgzf_fp, '\n', line);
        offset = bgzf_tell (bgzf_fp);
        chunk_count++;
        // stop if we have encountered an empty line
        if (eof <= 0)
        {
            if (bgzf_check_EOF(bgzf_fp) == 1) {
                if (offset > prev_offset) {
                    total_lines++;
                    prev_offset = offset;
                }
                break;
            }
            //break;
        }
        // store the offset of this chunk start
        else if (chunk_count == CHUNK_SIZE)
        {
            chunk_positions.push_back(prev_offset);
            chunk_count = 0;
        }
        total_lines++;
        prev_offset = offset;
    }
    chunk_positions.push_back (prev_offset);
    bgzf_close(bgzf_fp);

    index_file << total_lines << endl;
    for (size_t i = 0; i < chunk_positions.size(); ++i)
    {
        index_file << chunk_positions[i] << endl;
    }
    index_file.close();

    return std::rename((bgzf_file + ".gbi.tmp").c_str(), (bgzf_file + ".gbi").c_str());
}

/*
Load an existing gbi index for the file to facilitate
random access via the BGZF seek utility
*/
void load_index(string bgzf_file, index_info &index)
{
    string index_file_name = bgzf_file + ".gbi";
    // open the index file for reading
    ifstream index_file(index_file_name.c_str(), ios::in);

    if ( !index_file ) {
        cerr << "[grabix] could not find index file: " << index_file_name << ". Exiting!" << endl;
        exit (1);
    }
    else {
        string line;
        getline (index_file, line);
        index.header_end = atol(line.c_str());

        getline (index_file, line);
        index.num_lines = atol(line.c_str());

        while (index_file >> line)
        {
            index.chunk_offsets.push_back(atol(line.c_str()));
        }
    }
    index_file.close();
}


/*
Extract lines [FROM, TO] from file.
*/
int grab(string bgzf_file, int64_t from_line, int64_t to_line)
{
    // load index into vector of offsets
    index_info index;
    load_index(bgzf_file, index);

    if (((int) from_line > index.num_lines)
        ||
        ((int) to_line > index.num_lines))
    {
        cerr << "[grabix] requested lines exceed the number of lines in the file." << endl;
        exit(1);
    }
    else if (from_line < 0)
    {
        cerr << "[grabix] indexes must be positive numbers." << endl;
        exit(1);
    }
    else if (from_line > to_line)
    {
        cerr << "[grabix] requested end line is less than the requested begin line." << endl;
        exit(1);
    }
    else {

        // load the BGZF file
        BGZF *bgzf_fp = bgzf_open(bgzf_file.c_str(), "r");
        if (bgzf_fp == NULL)
        {
            cerr << "[grabix] could not open file: " << bgzf_file << endl;
            exit (1);
        }

        // dump the header if there is one
        int status;
        kstring_t *line = new kstring_t;
        line->s = '\0';
        line->l = 0;
        line->m = 0;

        while ((status = bgzf_getline(bgzf_fp, '\n', line)) != 0)
        {
            if (line->s[0] == '#')
                printf("%s\n", line->s);
            else break;
        }

        // easier to work in 0-based space
        int64_t from_line_0  = from_line - 1;
        // get the chunk index for the requested line
        int64_t requested_chunk = from_line_0 / CHUNK_SIZE;
        // derive the first line in that chunk
        int64_t chunk_line_start = (requested_chunk * CHUNK_SIZE);

        // jump to the correct offset for the relevant chunk
        // and fast forward until we find the requested line
        bgzf_seek (bgzf_fp, index.chunk_offsets[requested_chunk], SEEK_SET);
        while (chunk_line_start <= from_line_0)
        {
            status = bgzf_getline(bgzf_fp, '\n', line);
            chunk_line_start++;
        }
        // now, print each line until we reach the end of the requested block
        do
        {
            printf("%s\n", line->s);
            status = bgzf_getline(bgzf_fp, '\n', line);
            chunk_line_start++;
        } while (chunk_line_start <= to_line);
    }
    return EXIT_SUCCESS;
}


/*
Extract K random lines from file using reservoir sampling
*/
int random(string bgzf_file, uint64_t K)
{
    // load index into vector of offsets
    index_info index;
    load_index(bgzf_file, index);

    if ((int64_t) K > index.num_lines)
    {
        cerr << "[grabix] warning: requested more lines than in the file." << endl;
        exit(1);
    }
    else {
        // load the BGZF file
        BGZF *bgzf_fp = bgzf_open(bgzf_file.c_str(), "r");
        if (bgzf_fp == NULL)
        {
            cerr << "[grabix] could not open file: " << bgzf_file << endl;
            exit (1);
        }

        // seed our random number generator
        size_t seed = (unsigned)time(0)+(unsigned)getpid();
        srand(seed);

        // reservoir sample
        uint64_t s = 0;
        uint64_t N = 0;
        uint64_t result_size = 0;
        vector<string> sample;
        int status;
        kstring_t *line = new kstring_t;
        line->s = '\0';
        line->l = 0;
        line->m = 0;

        while ((status = bgzf_getline(bgzf_fp, '\n', line)) != 0)
        {
            if (line->s[0] == '#')
                printf("%s\n", line->s);
            else break;
        }

        while ((status = bgzf_getline(bgzf_fp, '\n', line)) != 0)
        {
            N++;

            if (status < 0)
                break;

            if (result_size < K)
            {
                sample.push_back(line->s);
                result_size++;
            }
            else
            {
                s = (int) ((double)rand()/(double)RAND_MAX * N);
                if (s < K)
                    sample[s] = line->s;
            }
        }
        bgzf_close(bgzf_fp);

        // report the sample
        for (size_t i = 0; i < sample.size(); ++i)
            printf("%s\n", sample[i].c_str());

    }
    return EXIT_SUCCESS;
}

/*
Return the total number of records in the index.
*/
int size(string bgzf_file)
{
  index_info index;
  load_index(bgzf_file, index);

  return index.num_lines;
}