///////////////////////////////////////////////////////////////////////////////
//
/// \file       stream_encoder.c
/// \brief      Encodes .xz Streams
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "block_encoder.h"
#include "index_encoder.h"


typedef struct {
    enum {
        SEQ_STREAM_HEADER,
        SEQ_BLOCK_INIT,
        SEQ_BLOCK_HEADER,
        SEQ_BLOCK_ENCODE,
        SEQ_INDEX_ENCODE,
        SEQ_STREAM_FOOTER,
    } sequence;

    /// True if Block encoder has been initialized by
    /// stream_encoder_init() or stream_encoder_update()
    /// and thus doesn't need to be initialized in stream_encode().
    bool block_encoder_is_initialized;

    /// Block
    lzma_next_coder block_encoder;

    /// Options for the Block encoder
    lzma_block block_options;

    /// The filter chain currently in use
    lzma_filter filters[LZMA_FILTERS_MAX + 1];

    /// Index encoder. This is separate from Block encoder, because this
    /// doesn't take much memory, and when encoding multiple Streams
    /// with the same encoding options we avoid reallocating memory.
    lzma_next_coder index_encoder;

    /// Index to hold sizes of the Blocks
    lzma_index *index;

    /// Read position in buffer[]
    size_t buffer_pos;

    /// Total number of bytes in buffer[]
    size_t buffer_size;

    /// Buffer to hold Stream Header, Block Header, and Stream Footer.
    /// Block Header has biggest maximum size.
    uint8_t buffer[LZMA_BLOCK_HEADER_SIZE_MAX];
} lzma_stream_coder;


static lzma_ret
block_encoder_init(lzma_stream_coder *coder, const lzma_allocator *allocator)
{
    // Prepare the Block options. Even though Block encoder doesn't need
    // compressed_size, uncompressed_size, and header_size to be
    // initialized, it is a good idea to do it here, because this way
    // we catch if someone gave us Filter ID that cannot be used in
    // Blocks/Streams.
    coder->block_options.compressed_size = LZMA_VLI_UNKNOWN;
    coder->block_options.uncompressed_size = LZMA_VLI_UNKNOWN;

    return_if_error(lzma_block_header_size(&coder->block_options));

    // Initialize the actual Block encoder.
    return lzma_block_encoder_init(&coder->block_encoder, allocator,
            &coder->block_options);
}


static lzma_ret
stream_encode(void *coder_ptr, const lzma_allocator *allocator,
        const uint8_t *restrict in, size_t *restrict in_pos,
        size_t in_size, uint8_t *restrict out,
        size_t *restrict out_pos, size_t out_size, lzma_action action)
{
    lzma_stream_coder *coder = coder_ptr;

    // Main loop
    while (*out_pos < out_size)
    switch (coder->sequence) {
    case SEQ_STREAM_HEADER:
    case SEQ_BLOCK_HEADER:
    case SEQ_STREAM_FOOTER:
        lzma_bufcpy(coder->buffer, &coder->buffer_pos,
                coder->buffer_size, out, out_pos, out_size);
        if (coder->buffer_pos < coder->buffer_size)
            return LZMA_OK;

        if (coder->sequence == SEQ_STREAM_FOOTER)
            return LZMA_STREAM_END;

        coder->buffer_pos = 0;
        ++coder->sequence;
        break;

    case SEQ_BLOCK_INIT: {
        if (*in_pos == in_size) {
            // If we are requested to flush or finish the current
            // Block, return LZMA_STREAM_END immediately since
            // there's nothing to do.
            if (action != LZMA_FINISH)
                return action == LZMA_RUN
                        ? LZMA_OK : LZMA_STREAM_END;

            // The application had used LZMA_FULL_FLUSH to finish
            // the previous Block, but now wants to finish without
            // encoding new data, or it is simply creating an
            // empty Stream with no Blocks.
            //
            // Initialize the Index encoder, and continue to
            // actually encoding the Index.
            return_if_error(lzma_index_encoder_init(
                    &coder->index_encoder, allocator,
                    coder->index));
            coder->sequence = SEQ_INDEX_ENCODE;
            break;
        }

        // Initialize the Block encoder unless it was already
        // initialized by stream_encoder_init() or
        // stream_encoder_update().
        if (!coder->block_encoder_is_initialized)
            return_if_error(block_encoder_init(coder, allocator));

        // Make it false so that we don't skip the initialization
        // with the next Block.
        coder->block_encoder_is_initialized = false;

        // Encode the Block Header. This shouldn't fail since we have
        // already initialized the Block encoder.
        if (lzma_block_header_encode(&coder->block_options,
                coder->buffer) != LZMA_OK)
            return LZMA_PROG_ERROR;

        coder->buffer_size = coder->block_options.header_size;
        coder->sequence = SEQ_BLOCK_HEADER;
        break;
    }

    case SEQ_BLOCK_ENCODE: {
        static const lzma_action convert[LZMA_ACTION_MAX + 1] = {
            LZMA_RUN,
            LZMA_SYNC_FLUSH,
            LZMA_FINISH,
            LZMA_FINISH,
            LZMA_FINISH,
        };

        const lzma_ret ret = coder->block_encoder.code(
                coder->block_encoder.coder, allocator,
                in, in_pos, in_size,
                out, out_pos, out_size, convert[action]);
        if (ret != LZMA_STREAM_END || action == LZMA_SYNC_FLUSH)
            return ret;

        // Add a new Index Record.
        const lzma_vli unpadded_size = lzma_block_unpadded_size(
                &coder->block_options);
        assert(unpadded_size != 0);
        return_if_error(lzma_index_append(coder->index, allocator,
                unpadded_size,
                coder->block_options.uncompressed_size));

        coder->sequence = SEQ_BLOCK_INIT;
        break;
    }

    case SEQ_INDEX_ENCODE: {
        // Call the Index encoder. It doesn't take any input, so
        // those pointers can be NULL.
        const lzma_ret ret = coder->index_encoder.code(
                coder->index_encoder.coder, allocator,
                NULL, NULL, 0,
                out, out_pos, out_size, LZMA_RUN);
        if (ret != LZMA_STREAM_END)
            return ret;

        // Encode the Stream Footer into coder->buffer.
        const lzma_stream_flags stream_flags = {
            .version = 0,
            .backward_size = lzma_index_size(coder->index),
            .check = coder->block_options.check,
        };

        if (lzma_stream_footer_encode(&stream_flags, coder->buffer)
                != LZMA_OK)
            return LZMA_PROG_ERROR;

        coder->buffer_size = LZMA_STREAM_HEADER_SIZE;
        coder->sequence = SEQ_STREAM_FOOTER;
        break;
    }

    default:
        assert(0);
        return LZMA_PROG_ERROR;
    }

    return LZMA_OK;
}


static void
stream_encoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
    lzma_stream_coder *coder = coder_ptr;

    lzma_next_end(&coder->block_encoder, allocator);
    lzma_next_end(&coder->index_encoder, allocator);
    lzma_index_end(coder->index, allocator);

    for (size_t i = 0; coder->filters[i].id != LZMA_VLI_UNKNOWN; ++i)
        lzma_free(coder->filters[i].options, allocator);

    lzma_free(coder, allocator);
    return;
}


static lzma_ret
stream_encoder_update(void *coder_ptr, const lzma_allocator *allocator,
        const lzma_filter *filters,
        const lzma_filter *reversed_filters)
{
    lzma_stream_coder *coder = coder_ptr;

    if (coder->sequence <= SEQ_BLOCK_INIT) {
        // There is no incomplete Block waiting to be finished,
        // thus we can change the whole filter chain. Start by
        // trying to initialize the Block encoder with the new
        // chain. This way we detect if the chain is valid.
        coder->block_encoder_is_initialized = false;
        coder->block_options.filters = (lzma_filter *)(filters);
        const lzma_ret ret = block_encoder_init(coder, allocator);
        coder->block_options.filters = coder->filters;
        if (ret != LZMA_OK)
            return ret;

        coder->block_encoder_is_initialized = true;

    } else if (coder->sequence <= SEQ_BLOCK_ENCODE) {
        // We are in the middle of a Block. Try to update only
        // the filter-specific options.
        return_if_error(coder->block_encoder.update(
                coder->block_encoder.coder, allocator,
                filters, reversed_filters));
    } else {
        // Trying to update the filter chain when we are already
        // encoding Index or Stream Footer.
        return LZMA_PROG_ERROR;
    }

    // Free the copy of the old chain and make a copy of the new chain.
    for (size_t i = 0; coder->filters[i].id != LZMA_VLI_UNKNOWN; ++i)
        lzma_free(coder->filters[i].options, allocator);

    return lzma_filters_copy(filters, coder->filters, allocator);
}


static lzma_ret
stream_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
        const lzma_filter *filters, lzma_check check)
{
    lzma_next_coder_init(&stream_encoder_init, next, allocator);

    if (filters == NULL)
        return LZMA_PROG_ERROR;

    lzma_stream_coder *coder = next->coder;

    if (coder == NULL) {
        coder = lzma_alloc(sizeof(lzma_stream_coder), allocator);
        if (coder == NULL)
            return LZMA_MEM_ERROR;

        next->coder = coder;
        next->code = &stream_encode;
        next->end = &stream_encoder_end;
        next->update = &stream_encoder_update;

        coder->filters[0].id = LZMA_VLI_UNKNOWN;
        coder->block_encoder = LZMA_NEXT_CODER_INIT;
        coder->index_encoder = LZMA_NEXT_CODER_INIT;
        coder->index = NULL;
    }

    // Basic initializations
    coder->sequence = SEQ_STREAM_HEADER;
    coder->block_options.version = 0;
    coder->block_options.check = check;

    // Initialize the Index
    lzma_index_end(coder->index, allocator);
    coder->index = lzma_index_init(allocator);
    if (coder->index == NULL)
        return LZMA_MEM_ERROR;

    // Encode the Stream Header
    lzma_stream_flags stream_flags = {
        .version = 0,
        .check = check,
    };
    return_if_error(lzma_stream_header_encode(
            &stream_flags, coder->buffer));

    coder->buffer_pos = 0;
    coder->buffer_size = LZMA_STREAM_HEADER_SIZE;

    // Initialize the Block encoder. This way we detect unsupported
    // filter chains when initializing the Stream encoder instead of
    // giving an error after Stream Header has already written out.
    return stream_encoder_update(coder, allocator, filters, NULL);
}


extern LZMA_API(lzma_ret)
lzma_stream_encoder(lzma_stream *strm,
        const lzma_filter *filters, lzma_check check)
{
    lzma_next_strm_init(stream_encoder_init, strm, filters, check);

    strm->internal->supported_actions[LZMA_RUN] = true;
    strm->internal->supported_actions[LZMA_SYNC_FLUSH] = true;
    strm->internal->supported_actions[LZMA_FULL_FLUSH] = true;
    strm->internal->supported_actions[LZMA_FULL_BARRIER] = true;
    strm->internal->supported_actions[LZMA_FINISH] = true;

    return LZMA_OK;
}
