/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

#include "method.h"

#include <stdio.h>
#include <stdlib.h>

#define ZSTD_STATIC_LINKING_ONLY
#include <zstd.h>

#define MIN(x, y) ((x) < (y) ? (x) : (y))

static char const* g_zstdcli = NULL;

void method_set_zstdcli(char const* zstdcli) {
    g_zstdcli = zstdcli;
}

/**
 * Macro to get a pointer of type, given ptr, which is a member variable with
 * the given name, member.
 *
 *     method_state_t* base = ...;
 *     buffer_state_t* state = container_of(base, buffer_state_t, base);
 */
#define container_of(ptr, type, member) \
    ((type*)(ptr == NULL ? NULL : (char*)(ptr)-offsetof(type, member)))

/** State to reuse the same buffers between compression calls. */
typedef struct {
    method_state_t base;
    data_buffers_t inputs; /**< The input buffer for each file. */
    data_buffer_t dictionary; /**< The dictionary. */
    data_buffer_t compressed; /**< The compressed data buffer. */
    data_buffer_t decompressed; /**< The decompressed data buffer. */
} buffer_state_t;

static size_t buffers_max_size(data_buffers_t buffers) {
    size_t max = 0;
    for (size_t i = 0; i < buffers.size; ++i) {
        if (buffers.buffers[i].size > max)
            max = buffers.buffers[i].size;
    }
    return max;
}

static method_state_t* buffer_state_create(data_t const* data) {
    buffer_state_t* state = (buffer_state_t*)calloc(1, sizeof(buffer_state_t));
    if (state == NULL)
        return NULL;
    state->base.data = data;
    state->inputs = data_buffers_get(data);
    state->dictionary = data_buffer_get_dict(data);
    size_t const max_size = buffers_max_size(state->inputs);
    state->compressed = data_buffer_create(ZSTD_compressBound(max_size));
    state->decompressed = data_buffer_create(max_size);
    return &state->base;
}

static void buffer_state_destroy(method_state_t* base) {
    if (base == NULL)
        return;
    buffer_state_t* state = container_of(base, buffer_state_t, base);
    free(state);
}

static int buffer_state_bad(
    buffer_state_t const* state,
    config_t const* config) {
    if (state == NULL) {
        fprintf(stderr, "buffer_state_t is NULL\n");
        return 1;
    }
    if (state->inputs.size == 0 || state->compressed.data == NULL ||
        state->decompressed.data == NULL) {
        fprintf(stderr, "buffer state allocation failure\n");
        return 1;
    }
    if (config->use_dictionary && state->dictionary.data == NULL) {
        fprintf(stderr, "dictionary loading failed\n");
        return 1;
    }
    return 0;
}

static result_t simple_compress(method_state_t* base, config_t const* config) {
    buffer_state_t* state = container_of(base, buffer_state_t, base);

    if (buffer_state_bad(state, config))
        return result_error(result_error_system_error);

    /* Keep the tests short by skipping directories, since behavior shouldn't
     * change.
     */
    if (base->data->type != data_type_file)
        return result_error(result_error_skip);
    
    if (config->advanced_api_only)
        return result_error(result_error_skip);

    if (config->use_dictionary || config->no_pledged_src_size)
        return result_error(result_error_skip);

    /* If the config doesn't specify a level, skip. */
    int const level = config_get_level(config);
    if (level == CONFIG_NO_LEVEL)
        return result_error(result_error_skip);

    data_buffer_t const input = state->inputs.buffers[0];

    /* Compress, decompress, and check the result. */
    state->compressed.size = ZSTD_compress(
        state->compressed.data,
        state->compressed.capacity,
        input.data,
        input.size,
        level);
    if (ZSTD_isError(state->compressed.size))
        return result_error(result_error_compression_error);

    state->decompressed.size = ZSTD_decompress(
        state->decompressed.data,
        state->decompressed.capacity,
        state->compressed.data,
        state->compressed.size);
    if (ZSTD_isError(state->decompressed.size))
        return result_error(result_error_decompression_error);
    if (data_buffer_compare(input, state->decompressed))
        return result_error(result_error_round_trip_error);

    result_data_t data;
    data.total_size = state->compressed.size;
    return result_data(data);
}

static result_t compress_cctx_compress(
    method_state_t* base,
    config_t const* config) {
    buffer_state_t* state = container_of(base, buffer_state_t, base);

    if (buffer_state_bad(state, config))
        return result_error(result_error_system_error);

    if (config->no_pledged_src_size)
        return result_error(result_error_skip);

    if (base->data->type != data_type_dir)
        return result_error(result_error_skip);
    
    if (config->advanced_api_only)
        return result_error(result_error_skip);

    int const level = config_get_level(config);

    ZSTD_CCtx* cctx = ZSTD_createCCtx();
    ZSTD_DCtx* dctx = ZSTD_createDCtx();
    if (cctx == NULL || dctx == NULL) {
        fprintf(stderr, "context creation failed\n");
        return result_error(result_error_system_error);
    }

    result_t result;
    result_data_t data = {.total_size = 0};
    for (size_t i = 0; i < state->inputs.size; ++i) {
        data_buffer_t const input = state->inputs.buffers[i];
        ZSTD_parameters const params =
            config_get_zstd_params(config, input.size, state->dictionary.size);

        if (level == CONFIG_NO_LEVEL)
            state->compressed.size = ZSTD_compress_advanced(
                cctx,
                state->compressed.data,
                state->compressed.capacity,
                input.data,
                input.size,
                config->use_dictionary ? state->dictionary.data : NULL,
                config->use_dictionary ? state->dictionary.size : 0,
                params);
        else if (config->use_dictionary)
            state->compressed.size = ZSTD_compress_usingDict(
                cctx,
                state->compressed.data,
                state->compressed.capacity,
                input.data,
                input.size,
                state->dictionary.data,
                state->dictionary.size,
                level);
        else
            state->compressed.size = ZSTD_compressCCtx(
                cctx,
                state->compressed.data,
                state->compressed.capacity,
                input.data,
                input.size,
                level);

        if (ZSTD_isError(state->compressed.size)) {
            result = result_error(result_error_compression_error);
            goto out;
        }

        if (config->use_dictionary)
            state->decompressed.size = ZSTD_decompress_usingDict(
                dctx,
                state->decompressed.data,
                state->decompressed.capacity,
                state->compressed.data,
                state->compressed.size,
                state->dictionary.data,
                state->dictionary.size);
        else
            state->decompressed.size = ZSTD_decompressDCtx(
                dctx,
                state->decompressed.data,
                state->decompressed.capacity,
                state->compressed.data,
                state->compressed.size);
        if (ZSTD_isError(state->decompressed.size)) {
            result = result_error(result_error_decompression_error);
            goto out;
        }
        if (data_buffer_compare(input, state->decompressed)) {
            result = result_error(result_error_round_trip_error);
            goto out;
        }

        data.total_size += state->compressed.size;
    }

    result = result_data(data);
out:
    ZSTD_freeCCtx(cctx);
    ZSTD_freeDCtx(dctx);
    return result;
}

/** Generic state creation function. */
static method_state_t* method_state_create(data_t const* data) {
    method_state_t* state = (method_state_t*)malloc(sizeof(method_state_t));
    if (state == NULL)
        return NULL;
    state->data = data;
    return state;
}

static void method_state_destroy(method_state_t* state) {
    free(state);
}

static result_t cli_compress(method_state_t* state, config_t const* config) {
    if (config->cli_args == NULL)
        return result_error(result_error_skip);

    if (config->advanced_api_only)
        return result_error(result_error_skip);

    /* We don't support no pledged source size with directories. Too slow. */
    if (state->data->type == data_type_dir && config->no_pledged_src_size)
        return result_error(result_error_skip);

    if (g_zstdcli == NULL)
        return result_error(result_error_system_error);

    /* '<zstd>' -cqr <args> [-D '<dict>'] '<file/dir>' */
    char cmd[1024];
    size_t const cmd_size = snprintf(
        cmd,
        sizeof(cmd),
        "'%s' -cqr %s %s%s%s %s '%s'",
        g_zstdcli,
        config->cli_args,
        config->use_dictionary ? "-D '" : "",
        config->use_dictionary ? state->data->dict.path : "",
        config->use_dictionary ? "'" : "",
        config->no_pledged_src_size ? "<" : "",
        state->data->data.path);
    if (cmd_size >= sizeof(cmd)) {
        fprintf(stderr, "command too large: %s\n", cmd);
        return result_error(result_error_system_error);
    }
    FILE* zstd = popen(cmd, "r");
    if (zstd == NULL) {
        fprintf(stderr, "failed to popen command: %s\n", cmd);
        return result_error(result_error_system_error);
    }

    char out[4096];
    size_t total_size = 0;
    while (1) {
        size_t const size = fread(out, 1, sizeof(out), zstd);
        total_size += size;
        if (size != sizeof(out))
            break;
    }
    if (ferror(zstd) || pclose(zstd) != 0) {
        fprintf(stderr, "zstd failed with command: %s\n", cmd);
        return result_error(result_error_compression_error);
    }

    result_data_t const data = {.total_size = total_size};
    return result_data(data);
}

static int advanced_config(
    ZSTD_CCtx* cctx,
    buffer_state_t* state,
    config_t const* config) {
    ZSTD_CCtx_reset(cctx, ZSTD_reset_session_and_parameters);
    for (size_t p = 0; p < config->param_values.size; ++p) {
        param_value_t const pv = config->param_values.data[p];
        if (ZSTD_isError(ZSTD_CCtx_setParameter(cctx, pv.param, pv.value))) {
            return 1;
        }
    }
    if (config->use_dictionary) {
        if (ZSTD_isError(ZSTD_CCtx_loadDictionary(
                cctx, state->dictionary.data, state->dictionary.size))) {
            return 1;
        }
    }
    return 0;
}

static result_t advanced_one_pass_compress_output_adjustment(
    method_state_t* base,
    config_t const* config,
    size_t const subtract) {
    buffer_state_t* state = container_of(base, buffer_state_t, base);

    if (buffer_state_bad(state, config))
        return result_error(result_error_system_error);

    ZSTD_CCtx* cctx = ZSTD_createCCtx();
    result_t result;

    if (!cctx || advanced_config(cctx, state, config)) {
        result = result_error(result_error_compression_error);
        goto out;
    }

    result_data_t data = {.total_size = 0};
    for (size_t i = 0; i < state->inputs.size; ++i) {
        data_buffer_t const input = state->inputs.buffers[i];

        if (!config->no_pledged_src_size) {
            if (ZSTD_isError(ZSTD_CCtx_setPledgedSrcSize(cctx, input.size))) {
                result = result_error(result_error_compression_error);
                goto out;
            }
        }
        size_t const size = ZSTD_compress2(
            cctx,
            state->compressed.data,
            ZSTD_compressBound(input.size) - subtract,
            input.data,
            input.size);
        if (ZSTD_isError(size)) {
            result = result_error(result_error_compression_error);
            goto out;
        }
        data.total_size += size;
    }

    result = result_data(data);
out:
    ZSTD_freeCCtx(cctx);
    return result;
}

static result_t advanced_one_pass_compress(
    method_state_t* base,
    config_t const* config) {
  return advanced_one_pass_compress_output_adjustment(base, config, 0);
}

static result_t advanced_one_pass_compress_small_output(
    method_state_t* base,
    config_t const* config) {
  return advanced_one_pass_compress_output_adjustment(base, config, 1);
}

static result_t advanced_streaming_compress(
    method_state_t* base,
    config_t const* config) {
    buffer_state_t* state = container_of(base, buffer_state_t, base);

    if (buffer_state_bad(state, config))
        return result_error(result_error_system_error);

    ZSTD_CCtx* cctx = ZSTD_createCCtx();
    result_t result;

    if (!cctx || advanced_config(cctx, state, config)) {
        result = result_error(result_error_compression_error);
        goto out;
    }

    result_data_t data = {.total_size = 0};
    for (size_t i = 0; i < state->inputs.size; ++i) {
        data_buffer_t input = state->inputs.buffers[i];

        if (!config->no_pledged_src_size) {
            if (ZSTD_isError(ZSTD_CCtx_setPledgedSrcSize(cctx, input.size))) {
                result = result_error(result_error_compression_error);
                goto out;
            }
        }

        while (input.size > 0) {
            ZSTD_inBuffer in = {input.data, MIN(input.size, 4096)};
            input.data += in.size;
            input.size -= in.size;
            ZSTD_EndDirective const op =
                input.size > 0 ? ZSTD_e_continue : ZSTD_e_end;
            size_t ret = 0;
            while (in.pos < in.size || (op == ZSTD_e_end && ret != 0)) {
                ZSTD_outBuffer out = {state->compressed.data,
                                      MIN(state->compressed.capacity, 1024)};
                ret = ZSTD_compressStream2(cctx, &out, &in, op);
                if (ZSTD_isError(ret)) {
                    result = result_error(result_error_compression_error);
                    goto out;
                }
                data.total_size += out.pos;
            }
        }
    }

    result = result_data(data);
out:
    ZSTD_freeCCtx(cctx);
    return result;
}

static int init_cstream(
    buffer_state_t* state,
    ZSTD_CStream* zcs,
    config_t const* config,
    int const advanced,
    ZSTD_CDict** cdict)
{
    size_t zret;
    if (advanced) {
        ZSTD_parameters const params = config_get_zstd_params(config, 0, 0);
        ZSTD_CDict* dict = NULL;
        if (cdict) {
            if (!config->use_dictionary)
              return 1;
            *cdict = ZSTD_createCDict_advanced(
                state->dictionary.data,
                state->dictionary.size,
                ZSTD_dlm_byRef,
                ZSTD_dct_auto,
                params.cParams,
                ZSTD_defaultCMem);
            if (!*cdict) {
                return 1;
            }
            zret = ZSTD_initCStream_usingCDict_advanced(
                zcs, *cdict, params.fParams, ZSTD_CONTENTSIZE_UNKNOWN);
        } else {
            zret = ZSTD_initCStream_advanced(
                zcs,
                config->use_dictionary ? state->dictionary.data : NULL,
                config->use_dictionary ? state->dictionary.size : 0,
                params,
                ZSTD_CONTENTSIZE_UNKNOWN);
        }
    } else {
        int const level = config_get_level(config);
        if (level == CONFIG_NO_LEVEL)
            return 1;
        if (cdict) {
            if (!config->use_dictionary)
              return 1;
            *cdict = ZSTD_createCDict(
                state->dictionary.data,
                state->dictionary.size,
                level);
            if (!*cdict) {
                return 1;
            }
            zret = ZSTD_initCStream_usingCDict(zcs, *cdict);
        } else if (config->use_dictionary) {
            zret = ZSTD_initCStream_usingDict(
                zcs,
                state->dictionary.data,
                state->dictionary.size,
                level);
        } else {
            zret = ZSTD_initCStream(zcs, level);
        }
    }
    if (ZSTD_isError(zret)) {
        return 1;
    }
    return 0;
}

static result_t old_streaming_compress_internal(
    method_state_t* base,
    config_t const* config,
    int const advanced,
    int const cdict) {
  buffer_state_t* state = container_of(base, buffer_state_t, base);

  if (buffer_state_bad(state, config))
    return result_error(result_error_system_error);


  ZSTD_CStream* zcs = ZSTD_createCStream();
  ZSTD_CDict* cd = NULL;
  result_t result;
  if (zcs == NULL) {
    result = result_error(result_error_compression_error);
    goto out;
  }
  if (!advanced && config_get_level(config) == CONFIG_NO_LEVEL) {
    result = result_error(result_error_skip);
    goto out;
  }
  if (cdict && !config->use_dictionary) {
    result = result_error(result_error_skip);
    goto out;
  }
  if (config->advanced_api_only) {
    result = result_error(result_error_skip);
    goto out;
  }
  if (init_cstream(state, zcs, config, advanced, cdict ? &cd : NULL)) {
    result = result_error(result_error_compression_error);
    goto out;
  }

  result_data_t data = {.total_size = 0};
  for (size_t i = 0; i < state->inputs.size; ++i) {
    data_buffer_t input = state->inputs.buffers[i];
    size_t zret = ZSTD_resetCStream(
        zcs,
        config->no_pledged_src_size ? ZSTD_CONTENTSIZE_UNKNOWN : input.size);
    if (ZSTD_isError(zret)) {
      result = result_error(result_error_compression_error);
      goto out;
    }

    while (input.size > 0) {
      ZSTD_inBuffer in = {input.data, MIN(input.size, 4096)};
      input.data += in.size;
      input.size -= in.size;
      ZSTD_EndDirective const op =
          input.size > 0 ? ZSTD_e_continue : ZSTD_e_end;
      zret = 0;
      while (in.pos < in.size || (op == ZSTD_e_end && zret != 0)) {
        ZSTD_outBuffer out = {state->compressed.data,
                              MIN(state->compressed.capacity, 1024)};
        if (op == ZSTD_e_continue || in.pos < in.size)
          zret = ZSTD_compressStream(zcs, &out, &in);
        else
          zret = ZSTD_endStream(zcs, &out);
        if (ZSTD_isError(zret)) {
          result = result_error(result_error_compression_error);
          goto out;
        }
        data.total_size += out.pos;
      }
    }
  }

  result = result_data(data);
out:
    ZSTD_freeCStream(zcs);
    ZSTD_freeCDict(cd);
    return result;
}

static result_t old_streaming_compress(
    method_state_t* base,
    config_t const* config)
{
    return old_streaming_compress_internal(
        base, config, /* advanced */ 0, /* cdict */ 0);
}

static result_t old_streaming_compress_advanced(
    method_state_t* base,
    config_t const* config)
{
    return old_streaming_compress_internal(
        base, config, /* advanced */ 1, /* cdict */ 0);
}

static result_t old_streaming_compress_cdict(
    method_state_t* base,
    config_t const* config)
{
    return old_streaming_compress_internal(
        base, config, /* advanced */ 0, /* cdict */ 1);
}

static result_t old_streaming_compress_cdict_advanced(
    method_state_t* base,
    config_t const* config)
{
    return old_streaming_compress_internal(
        base, config, /* advanced */ 1, /* cdict */ 1);
}

method_t const simple = {
    .name = "compress simple",
    .create = buffer_state_create,
    .compress = simple_compress,
    .destroy = buffer_state_destroy,
};

method_t const compress_cctx = {
    .name = "compress cctx",
    .create = buffer_state_create,
    .compress = compress_cctx_compress,
    .destroy = buffer_state_destroy,
};

method_t const advanced_one_pass = {
    .name = "advanced one pass",
    .create = buffer_state_create,
    .compress = advanced_one_pass_compress,
    .destroy = buffer_state_destroy,
};

method_t const advanced_one_pass_small_out = {
    .name = "advanced one pass small out",
    .create = buffer_state_create,
    .compress = advanced_one_pass_compress,
    .destroy = buffer_state_destroy,
};

method_t const advanced_streaming = {
    .name = "advanced streaming",
    .create = buffer_state_create,
    .compress = advanced_streaming_compress,
    .destroy = buffer_state_destroy,
};

method_t const old_streaming = {
    .name = "old streaming",
    .create = buffer_state_create,
    .compress = old_streaming_compress,
    .destroy = buffer_state_destroy,
};

method_t const old_streaming_advanced = {
    .name = "old streaming advanced",
    .create = buffer_state_create,
    .compress = old_streaming_compress_advanced,
    .destroy = buffer_state_destroy,
};

method_t const old_streaming_cdict = {
    .name = "old streaming cdict",
    .create = buffer_state_create,
    .compress = old_streaming_compress_cdict,
    .destroy = buffer_state_destroy,
};

method_t const old_streaming_advanced_cdict = {
    .name = "old streaming advanced cdict",
    .create = buffer_state_create,
    .compress = old_streaming_compress_cdict_advanced,
    .destroy = buffer_state_destroy,
};

method_t const cli = {
    .name = "zstdcli",
    .create = method_state_create,
    .compress = cli_compress,
    .destroy = method_state_destroy,
};

static method_t const* g_methods[] = {
    &simple,
    &compress_cctx,
    &cli,
    &advanced_one_pass,
    &advanced_one_pass_small_out,
    &advanced_streaming,
    &old_streaming,
    &old_streaming_advanced,
    &old_streaming_cdict,
    &old_streaming_advanced_cdict,
    NULL,
};

method_t const* const* methods = g_methods;