// Copyright (c) 2011-2013, Pacific Biosciences of California, Inc.
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// Author: David Alexander

#include <algorithm>
#include <cassert>
#include <vector>

#include <ConsensusCore/Coverage.hpp>

using std::vector;

namespace ConsensusCore {

    void CoverageInWindow(int  tStartDim,
                          int *tStart,
                          int  tEndDim,
                          int *tEnd,
                          int  winStart,
                          int  winLen,
                          int *coverage)
    {
        using std::max;
        using std::min;

        assert (tStartDim == tEndDim);

        int nReads = tStartDim;
        int winEnd = winStart + winLen;
        std::fill_n(coverage, winLen, 0);
        for (int read = 0; read < nReads; read++)
        {
            int tStart_ = tStart[read];
            int tEnd_   = tEnd[read];
            for (int pos = max(tStart_, winStart); pos < min(tEnd_, winEnd); pos++)
            {
                coverage[pos-winStart] += 1;
            }
        }
    }


    #define CHUNK_SIZE 10000

    vector<Interval> CoveredIntervals(int minCoverage,
                                      int tStartDim,
                                      int *tStart,
                                      int tEndDim,
                                      int *tEnd,
                                      int winStart,
                                      int winLen)
    {
        assert (tStartDim == tEndDim);
        // assert(isSorted(tStart));  // find out how to get this ... it's C++11

        // Approach: divide into chunks, find coverage in each chunk,
        // then scan for covered windows ... careful to anneal windows
        // spanning chunk boundaries.  We also rely on the sortedness of the
        // tStart to restrict our attention to

        int winEnd = winStart + winLen;
        int coverage[CHUNK_SIZE];
        int currentIntervalStart = -1;
        vector<Interval> intervals;

        int startRowInChunk = 0;
        for (int chunkStart = winStart;
             chunkStart < winEnd;
             chunkStart += CHUNK_SIZE)
        {
            int chunkEnd = std::min(chunkStart + CHUNK_SIZE, winEnd);

            // We compute a conservative guess of the rows that are involved in
            // this chunk.  Not every row in the range [startRowInChunk, endRowInChunk)
            // actually overlaps the chunk, but no rows not in that range intersect the chunk.
            // startRowInChunk is computed by scanning from where it was for the last chunk.
            // This is the best we can do within pulling in the nBackRead stuff.
            int endRowInChunk = std::lower_bound(tStart, tStart + tStartDim, chunkEnd) - tStart;
            for (; ((startRowInChunk < endRowInChunk) & (tEnd[startRowInChunk] < chunkStart));
                 startRowInChunk++);

            CoverageInWindow((endRowInChunk-startRowInChunk), tStart+startRowInChunk,
                             (endRowInChunk-startRowInChunk), tEnd+startRowInChunk,
                             chunkStart, CHUNK_SIZE, coverage);
            int j = 0;
            while (j < (chunkEnd - chunkStart))
            {
                if (coverage[j] >= minCoverage)
                {
                    if (currentIntervalStart == -1)
                    {
                        currentIntervalStart = chunkStart + j;
                    }
                }
                else
                {
                    if (currentIntervalStart != -1)
                    {
                        intervals.push_back(Interval(currentIntervalStart, chunkStart + j));
                        currentIntervalStart = -1;
                    }
                }
                j++;
            }
        }
        if (currentIntervalStart != -1)
        {
            intervals.push_back(Interval(currentIntervalStart, winEnd));
        }
        return intervals;
    }
}
