#include "amduat/fps.h"

#include <stdlib.h>
#include <string.h>

static const char k_amduat_fps_domain_sep[] = "CAS:OBJ\0";

static uint8_t amduat_fps_reverse_bits8(uint8_t value) {
  value = (uint8_t)(((value & 0xf0u) >> 4) | ((value & 0x0fu) << 4));
  value = (uint8_t)(((value & 0xccu) >> 2) | ((value & 0x33u) << 2));
  value = (uint8_t)(((value & 0xaau) >> 1) | ((value & 0x55u) << 1));
  return value;
}

static bool amduat_fps_alloc_output(size_t len, amduat_octets_t *out) {
  uint8_t *buf;

  if (out == NULL) {
    return false;
  }
  *out = amduat_octets(NULL, 0u);
  if (len == 0u) {
    return true;
  }
  buf = (uint8_t *)malloc(len);
  if (buf == NULL) {
    return false;
  }
  *out = amduat_octets(buf, len);
  return true;
}

amduat_fps_error_t amduat_fps_slice(amduat_octets_t input,
                                    size_t offset,
                                    size_t length,
                                    amduat_octets_t *out) {
  if (out == NULL || (input.len != 0u && input.data == NULL)) {
    return AMDUAT_FPS_ERR_INVALID;
  }
  if (offset > input.len || length > input.len - offset) {
    return AMDUAT_FPS_ERR_SLICE_RANGE;
  }
  if (!amduat_fps_alloc_output(length, out)) {
    return AMDUAT_FPS_ERR_IO_FAILURE;
  }
  if (length != 0u) {
    memcpy((void *)out->data, input.data + offset, length);
  }
  return AMDUAT_FPS_OK;
}

amduat_fps_error_t amduat_fps_concat(const amduat_octets_t *inputs,
                                     size_t input_count,
                                     amduat_octets_t *out) {
  size_t total = 0u;
  size_t i;
  uint8_t *cursor;

  if (out == NULL) {
    return AMDUAT_FPS_ERR_INVALID;
  }
  if (input_count == 0u) {
    return AMDUAT_FPS_ERR_EMPTY_INPUTS;
  }
  if (inputs == NULL) {
    return AMDUAT_FPS_ERR_INVALID;
  }
  for (i = 0u; i < input_count; ++i) {
    if (inputs[i].len != 0u && inputs[i].data == NULL) {
      return AMDUAT_FPS_ERR_INVALID;
    }
    if (SIZE_MAX - total < inputs[i].len) {
      return AMDUAT_FPS_ERR_IO_FAILURE;
    }
    total += inputs[i].len;
  }
  if (!amduat_fps_alloc_output(total, out)) {
    return AMDUAT_FPS_ERR_IO_FAILURE;
  }
  cursor = (uint8_t *)out->data;
  for (i = 0u; i < input_count; ++i) {
    if (inputs[i].len != 0u) {
      memcpy(cursor, inputs[i].data, inputs[i].len);
      cursor += inputs[i].len;
    }
  }
  return AMDUAT_FPS_OK;
}

amduat_fps_error_t amduat_fps_reverse(amduat_octets_t input,
                                      amduat_fps_reverse_level_t level,
                                      amduat_octets_t *out) {
  size_t unit_size;
  size_t i;
  size_t unit_count;

  if (out == NULL || (input.len != 0u && input.data == NULL)) {
    return AMDUAT_FPS_ERR_INVALID;
  }

  if (level == AMDUAT_FPS_REVERSE_BITS) {
    if (!amduat_fps_alloc_output(input.len, out)) {
      return AMDUAT_FPS_ERR_IO_FAILURE;
    }
    for (i = 0u; i < input.len; ++i) {
      size_t dst = input.len - 1u - i;
      ((uint8_t *)out->data)[dst] = amduat_fps_reverse_bits8(input.data[i]);
    }
    return AMDUAT_FPS_OK;
  }

  if (level == AMDUAT_FPS_REVERSE_BYTES) {
    unit_size = 1u;
  } else if (level == AMDUAT_FPS_REVERSE_WORDS) {
    unit_size = 2u;
  } else if (level == AMDUAT_FPS_REVERSE_LONGS) {
    unit_size = 4u;
  } else {
    return AMDUAT_FPS_ERR_INVALID_LEVEL;
  }

  if (unit_size != 0u && input.len % unit_size != 0u) {
    return AMDUAT_FPS_ERR_REV_ALIGNMENT;
  }
  if (!amduat_fps_alloc_output(input.len, out)) {
    return AMDUAT_FPS_ERR_IO_FAILURE;
  }
  unit_count = unit_size == 0u ? 0u : input.len / unit_size;
  for (i = 0u; i < unit_count; ++i) {
    size_t src_offset = i * unit_size;
    size_t dst_offset = (unit_count - 1u - i) * unit_size;
    memcpy((uint8_t *)out->data + dst_offset,
           input.data + src_offset,
           unit_size);
  }
  return AMDUAT_FPS_OK;
}

amduat_fps_error_t amduat_fps_splice(amduat_octets_t a,
                                     size_t offset,
                                     amduat_octets_t b,
                                     amduat_octets_t *out) {
  size_t total;

  if (out == NULL ||
      (a.len != 0u && a.data == NULL) ||
      (b.len != 0u && b.data == NULL)) {
    return AMDUAT_FPS_ERR_INVALID;
  }
  if (offset > a.len) {
    return AMDUAT_FPS_ERR_SPLICE_RANGE;
  }
  if (SIZE_MAX - a.len < b.len) {
    return AMDUAT_FPS_ERR_IO_FAILURE;
  }
  total = a.len + b.len;
  if (!amduat_fps_alloc_output(total, out)) {
    return AMDUAT_FPS_ERR_IO_FAILURE;
  }
  if (offset != 0u) {
    memcpy((uint8_t *)out->data, a.data, offset);
  }
  if (b.len != 0u) {
    memcpy((uint8_t *)out->data + offset, b.data, b.len);
  }
  if (a.len > offset) {
    memcpy((uint8_t *)out->data + offset + b.len,
           a.data + offset,
           a.len - offset);
  }
  return AMDUAT_FPS_OK;
}

bool amduat_fps_cid_for_payload(amduat_hash_id_t hash_id,
                                amduat_octets_t payload,
                                amduat_reference_t *out_cid) {
  const amduat_hash_asl1_desc_t *desc;
  amduat_octets_t domain_sep;
  uint8_t *digest;

  if (out_cid == NULL) {
    return false;
  }
  *out_cid = amduat_reference(0, amduat_octets(NULL, 0u));
  desc = amduat_hash_asl1_desc_lookup(hash_id);
  if (desc == NULL || desc->digest_len == 0u) {
    return false;
  }
  digest = (uint8_t *)malloc(desc->digest_len);
  if (digest == NULL) {
    return false;
  }
  domain_sep = amduat_octets(k_amduat_fps_domain_sep,
                             sizeof(k_amduat_fps_domain_sep) - 1u);
  if (!amduat_hash_asl1_digest_domain(hash_id, domain_sep, payload, digest,
                                      desc->digest_len)) {
    free(digest);
    return false;
  }
  *out_cid = amduat_reference(hash_id, amduat_octets(digest, desc->digest_len));
  return true;
}