#ifndef PIECETABLE_H
#define PIECETABLE_H

#include <stdint.h>
#include "PagedBuffer.h"
#include <utility>

#define PIECE_DESCRIPTOR_INDEX_START    0u
#define PIECE_DESCRIPTOR_INDEX_END      1u

#define PIECE_DESCRIPTOR_N_CHARS_EOL_FLAG_MASK  0x80000000u

class PieceTable
{
public:
    struct PieceDescriptor
    {
        /** The previous piece descriptor in the chain. */
        PieceDescriptor * prev;

        /** The next piece descriptor in the chain. */
        PieceDescriptor * next;

        /** Text that the piece describes. */
        uint8_t * start;

        /** Length of the text (in bytes). */
        uint32_t length;

        /**
         * Number of characters in the text.
         * Also, the highest bit is the eol flag.
         */
        uint32_t n_chars;

        /** Get the number of characters pointed to by this descriptor. */
        uint32_t get_n_chars() { return n_chars & (~PIECE_DESCRIPTOR_N_CHARS_EOL_FLAG_MASK); }

        /** Get whether this descriptor is the end of a line. */
        bool eol() { return (n_chars & PIECE_DESCRIPTOR_N_CHARS_EOL_FLAG_MASK) != 0u; }

        /** Toggle whether this descriptor is the end of a line. */
        void toggle_eol() { n_chars ^= PIECE_DESCRIPTOR_N_CHARS_EOL_FLAG_MASK; }
    };

    struct Position
    {
        /** The piece. */
        PieceDescriptor * pd;

        /** Byte offset within the piece. */
        uint32_t offset;
    };

    struct ChangeDescriptor
    {
        uint32_t piece_descriptor_index;
        uint32_t from_val;
        uint32_t to_val;
        uint8_t attr_idx;
    };

    PieceTable(const uint8_t * file_buffer, unsigned long file_buffer_size);

    PieceDescriptor * add_piece_descriptor()
    {
        return &m_piece_descriptors[m_piece_descriptor_index++];
    }

    PieceDescriptor & operator[](uint32_t index)
    {
        return m_piece_descriptors[index];
    }

    uint32_t get_num_lines() { return m_num_lines; }

    PieceDescriptor * start_descriptor;
    PieceDescriptor * end_descriptor;

    Position cursor_position;

    void append_initial_line_piece(uint8_t * start, uint32_t length, uint32_t n_chars, bool eol);

protected:
    const uint8_t * m_file_buffer;
    unsigned long m_file_buffer_size;
    uint32_t m_num_lines;

    /** Next available piece descriptor index. */
    uint32_t m_piece_descriptor_index;

    PagedBuffer<uint8_t> m_append_buffer;
    PagedBuffer<PieceDescriptor> m_piece_descriptors;
    PagedBuffer<ChangeDescriptor> m_change_descriptors;
};

#endif