#include "amduat/fps.h"

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

typedef struct {
  const uint8_t *data;
  size_t len;
  size_t offset;
} cursor_t;

static bool read_file(const char *path, uint8_t **out_bytes, size_t *out_len) {
  FILE *fp;
  long size;
  uint8_t *buffer;
  size_t read_len;

  if (path == NULL || out_bytes == NULL || out_len == NULL) {
    return false;
  }
  *out_bytes = NULL;
  *out_len = 0u;

  fp = fopen(path, "rb");
  if (fp == NULL) {
    return false;
  }
  if (fseek(fp, 0, SEEK_END) != 0) {
    fclose(fp);
    return false;
  }
  size = ftell(fp);
  if (size < 0) {
    fclose(fp);
    return false;
  }
  if (fseek(fp, 0, SEEK_SET) != 0) {
    fclose(fp);
    return false;
  }

  buffer = (uint8_t *)malloc((size_t)size + 1u);
  if (buffer == NULL) {
    fclose(fp);
    return false;
  }
  read_len = fread(buffer, 1u, (size_t)size, fp);
  fclose(fp);
  if (read_len != (size_t)size) {
    free(buffer);
    return false;
  }
  buffer[size] = '\0';

  *out_bytes = buffer;
  *out_len = (size_t)size;
  return true;
}

static bool build_fixture_path(char *out, size_t out_len) {
  const char *needle = "/tests/enc/";
  const char *path = __FILE__;
  const char *pos = strstr(path, needle);
  size_t prefix_len;

  if (pos == NULL) {
    return false;
  }
  prefix_len = (size_t)(pos - path);
  if (prefix_len + strlen("/tests/fixtures/conformance/"
                          "fps_1/manifest.json") + 1u >
      out_len) {
    return false;
  }

  memcpy(out, path, prefix_len);
  out[prefix_len] = '\0';
  strcat(out, "/tests/fixtures/conformance/fps_1/manifest.json");
  return true;
}

static bool cursor_expect(cursor_t *cur, const char *literal) {
  size_t len = strlen(literal);
  if (cur->len - cur->offset < len) {
    return false;
  }
  if (memcmp(cur->data + cur->offset, literal, len) != 0) {
    return false;
  }
  cur->offset += len;
  return true;
}

static bool cursor_skip_ws(cursor_t *cur) {
  while (cur->offset < cur->len) {
    char c = (char)cur->data[cur->offset];
    if (c != ' ' && c != '\n' && c != '\r' && c != '\t') {
      break;
    }
    cur->offset++;
  }
  return true;
}

static bool cursor_read_string(cursor_t *cur, char **out) {
  size_t start;
  size_t end;
  char *buf;

  if (!cursor_skip_ws(cur) || cur->offset >= cur->len ||
      cur->data[cur->offset] != '"') {
    return false;
  }
  cur->offset++;
  start = cur->offset;
  while (cur->offset < cur->len && cur->data[cur->offset] != '"') {
    cur->offset++;
  }
  if (cur->offset >= cur->len) {
    return false;
  }
  end = cur->offset;
  cur->offset++;

  buf = (char *)malloc(end - start + 1u);
  if (buf == NULL) {
    return false;
  }
  memcpy(buf, cur->data + start, end - start);
  buf[end - start] = '\0';
  *out = buf;
  return true;
}

static bool cursor_read_number(cursor_t *cur, size_t *out) {
  size_t start;
  size_t value = 0u;
  bool has_digit = false;

  if (!cursor_skip_ws(cur)) {
    return false;
  }
  start = cur->offset;
  while (cur->offset < cur->len) {
    char c = (char)cur->data[cur->offset];
    if (c < '0' || c > '9') {
      break;
    }
    has_digit = true;
    value = value * 10u + (size_t)(c - '0');
    cur->offset++;
  }
  if (!has_digit || start == cur->offset) {
    return false;
  }
  *out = value;
  return true;
}

static bool hex_decode(const char *hex, uint8_t **out, size_t *out_len) {
  size_t len;
  size_t i;
  uint8_t *buf;

  if (hex == NULL || out == NULL || out_len == NULL) {
    return false;
  }
  len = strlen(hex);
  if (len % 2u != 0u) {
    return false;
  }
  buf = (uint8_t *)malloc(len / 2u);
  if (buf == NULL) {
    return false;
  }
  for (i = 0u; i < len; i += 2u) {
    unsigned int byte;
    if (sscanf(hex + i, "%2x", &byte) != 1) {
      free(buf);
      return false;
    }
    buf[i / 2u] = (uint8_t)byte;
  }
  *out = buf;
  *out_len = len / 2u;
  return true;
}

static bool hex_eq(const char *hex, amduat_octets_t bytes) {
  uint8_t *decoded = NULL;
  size_t decoded_len = 0u;
  bool ok = false;

  if (!hex_decode(hex, &decoded, &decoded_len)) {
    return false;
  }
  ok = decoded_len == bytes.len &&
       (decoded_len == 0u ||
        memcmp(decoded, bytes.data, decoded_len) == 0);
  free(decoded);
  return ok;
}

static bool cid_matches(const char *hex, amduat_octets_t output) {
  amduat_reference_t cid;
  size_t hex_len = strlen(hex);
  char *lower = NULL;
  char *scratch = NULL;
  bool ok = false;

  if (!amduat_fps_cid_for_payload(AMDUAT_HASH_ASL1_ID_SHA256, output, &cid)) {
    return false;
  }
  lower = (char *)malloc(hex_len + 1u);
  if (lower == NULL) {
    amduat_reference_free(&cid);
    return false;
  }
  scratch = (char *)malloc(cid.digest.len * 2u + 1u);
  if (scratch == NULL) {
    free(lower);
    amduat_reference_free(&cid);
    return false;
  }
  for (size_t i = 0u; i < hex_len; ++i) {
    char c = hex[i];
    if (c >= 'A' && c <= 'F') {
      c = (char)(c - 'A' + 'a');
    }
    lower[i] = c;
  }
  lower[hex_len] = '\0';
  for (size_t i = 0u; i < cid.digest.len; ++i) {
    sprintf(scratch + i * 2u, "%02x", cid.digest.data[i]);
  }
  ok = strcmp(lower, scratch) == 0;
  free(lower);
  free(scratch);
  amduat_reference_free(&cid);
  return ok;
}

static bool parse_manifest_cases(cursor_t *cur) {
  if (!cursor_skip_ws(cur) || cur->offset >= cur->len ||
      cur->data[cur->offset] != '[') {
    return false;
  }
  cur->offset++;
  while (true) {
    char *field = NULL;
    char *value = NULL;
    char *op = NULL;
    char *input = NULL;
    char *insert = NULL;
    char *output = NULL;
    char *cid_hex = NULL;
    char *level = NULL;
    char *inputs[4] = {0};
    size_t inputs_len = 0u;
    size_t offset = 0u;
    size_t length = 0u;
    bool has_offset = false;
    bool has_length = false;
    bool has_inputs = false;
    bool has_input = false;
    bool has_insert = false;
    bool has_level = false;
    bool has_output = false;
    bool has_cid = false;
    bool ok = true;

    if (!cursor_skip_ws(cur)) {
      return false;
    }
    if (cur->offset < cur->len && cur->data[cur->offset] == ']') {
      cur->offset++;
      return true;
    }
    if (cur->offset >= cur->len || cur->data[cur->offset] != '{') {
      return false;
    }
    cur->offset++;
    while (true) {
      if (!cursor_read_string(cur, &field)) {
        ok = false;
        break;
      }
      if (!cursor_skip_ws(cur) || cur->offset >= cur->len ||
          cur->data[cur->offset] != ':') {
        ok = false;
        break;
      }
      cur->offset++;
      if (strcmp(field, "id") == 0 ||
          strcmp(field, "op") == 0 || strcmp(field, "input") == 0 ||
          strcmp(field, "insert") == 0 || strcmp(field, "output") == 0 ||
          strcmp(field, "cid_sha256") == 0 || strcmp(field, "level") == 0) {
        if (!cursor_read_string(cur, &value)) {
          ok = false;
          break;
        }
        if (strcmp(field, "id") == 0) {
          free(value);
          value = NULL;
        } else if (strcmp(field, "op") == 0) {
          op = value;
        } else if (strcmp(field, "input") == 0) {
          input = value;
          has_input = true;
        } else if (strcmp(field, "insert") == 0) {
          insert = value;
          has_insert = true;
        } else if (strcmp(field, "output") == 0) {
          output = value;
          has_output = true;
        } else if (strcmp(field, "cid_sha256") == 0) {
          cid_hex = value;
          has_cid = true;
        } else {
          level = value;
          has_level = true;
        }
      } else if (strcmp(field, "offset") == 0 ||
                 strcmp(field, "length") == 0) {
        size_t num = 0u;
        if (!cursor_read_number(cur, &num)) {
          ok = false;
          break;
        }
        if (strcmp(field, "offset") == 0) {
          offset = num;
          has_offset = true;
        } else {
          length = num;
          has_length = true;
        }
      } else if (strcmp(field, "inputs") == 0) {
        if (!cursor_skip_ws(cur) || cur->offset >= cur->len ||
            cur->data[cur->offset] != '[') {
          ok = false;
          break;
        }
        cur->offset++;
        while (true) {
          if (!cursor_skip_ws(cur)) {
            ok = false;
            break;
          }
          if (cur->offset < cur->len && cur->data[cur->offset] == ']') {
            cur->offset++;
            break;
          }
          if (inputs_len >= 4u) {
            ok = false;
            break;
          }
          if (!cursor_read_string(cur, &inputs[inputs_len++])) {
            ok = false;
            break;
          }
          if (!cursor_skip_ws(cur)) {
            ok = false;
            break;
          }
          if (cur->offset < cur->len && cur->data[cur->offset] == ',') {
            cur->offset++;
            continue;
          }
        }
        has_inputs = true;
      } else {
        ok = false;
        break;
      }

      free(field);
      field = NULL;
      if (!cursor_skip_ws(cur)) {
        ok = false;
        break;
      }
      if (cur->offset < cur->len && cur->data[cur->offset] == ',') {
        cur->offset++;
        continue;
      }
      if (cur->offset < cur->len && cur->data[cur->offset] == '}') {
        cur->offset++;
        break;
      }
    }

    if (!ok || op == NULL || !has_output || !has_cid) {
      ok = false;
    }

    if (ok) {
      amduat_octets_t output_bytes = amduat_octets(NULL, 0u);
      amduat_octets_t out = amduat_octets(NULL, 0u);
      amduat_octets_t input_bytes = amduat_octets(NULL, 0u);
      amduat_octets_t insert_bytes = amduat_octets(NULL, 0u);
      uint8_t *decoded = NULL;
      size_t decoded_len = 0u;
      uint8_t *insert_decoded = NULL;
      size_t insert_len = 0u;

      if (!hex_decode(output, &decoded, &decoded_len)) {
        ok = false;
      } else {
        output_bytes = amduat_octets(decoded, decoded_len);
      }

      if (ok && !cid_matches(cid_hex, output_bytes)) {
        ok = false;
      }

      if (ok && strcmp(op, "slice") == 0) {
        if (!has_input || !has_offset || !has_length) {
          ok = false;
        } else if (!hex_decode(input, &decoded, &decoded_len)) {
          ok = false;
        } else {
          input_bytes = amduat_octets(decoded, decoded_len);
          if (amduat_fps_slice(input_bytes, offset, length, &out) !=
              AMDUAT_FPS_OK) {
            ok = false;
          } else if (!hex_eq(output, out)) {
            ok = false;
          }
        }
      } else if (ok && strcmp(op, "concat") == 0) {
        if (!has_inputs) {
          ok = false;
        } else {
          amduat_octets_t in_octets[4];
          for (size_t i = 0u; i < inputs_len; ++i) {
            if (!hex_decode(inputs[i], &decoded, &decoded_len)) {
              ok = false;
              break;
            }
            in_octets[i] = amduat_octets(decoded, decoded_len);
          }
          if (ok) {
            if (amduat_fps_concat(in_octets, inputs_len, &out) !=
                AMDUAT_FPS_OK) {
              ok = false;
            } else if (!hex_eq(output, out)) {
              ok = false;
            }
          }
          for (size_t i = 0u; i < inputs_len; ++i) {
            free((void *)in_octets[i].data);
          }
        }
      } else if (ok && strcmp(op, "reverse") == 0) {
        amduat_fps_reverse_level_t lvl = AMDUAT_FPS_REVERSE_BYTES;
        if (!has_input || !has_level) {
          ok = false;
        } else if (strcmp(level, "bit") == 0) {
          lvl = AMDUAT_FPS_REVERSE_BITS;
        } else if (strcmp(level, "byte") == 0) {
          lvl = AMDUAT_FPS_REVERSE_BYTES;
        } else if (strcmp(level, "word") == 0) {
          lvl = AMDUAT_FPS_REVERSE_WORDS;
        } else if (strcmp(level, "long") == 0) {
          lvl = AMDUAT_FPS_REVERSE_LONGS;
        } else {
          ok = false;
        }
        if (ok && !hex_decode(input, &decoded, &decoded_len)) {
          ok = false;
        }
        if (ok) {
          input_bytes = amduat_octets(decoded, decoded_len);
          if (amduat_fps_reverse(input_bytes, lvl, &out) != AMDUAT_FPS_OK) {
            ok = false;
          } else if (!hex_eq(output, out)) {
            ok = false;
          }
        }
      } else if (ok && strcmp(op, "splice") == 0) {
        if (!has_input || !has_insert || !has_offset) {
          ok = false;
        } else if (!hex_decode(input, &decoded, &decoded_len) ||
                   !hex_decode(insert, &insert_decoded, &insert_len)) {
          ok = false;
        } else {
          input_bytes = amduat_octets(decoded, decoded_len);
          insert_bytes = amduat_octets(insert_decoded, insert_len);
          if (amduat_fps_splice(input_bytes, offset, insert_bytes, &out) !=
              AMDUAT_FPS_OK) {
            ok = false;
          } else if (!hex_eq(output, out)) {
            ok = false;
          }
        }
      } else if (ok) {
        ok = false;
      }

      amduat_octets_free(&out);
      free((void *)output_bytes.data);
      if (input_bytes.data != NULL) {
        free((void *)input_bytes.data);
      }
      if (insert_bytes.data != NULL) {
        free((void *)insert_bytes.data);
      }
    }

    free(op);
    free(input);
    free(insert);
    free(output);
    free(cid_hex);
    free(level);
    for (size_t i = 0u; i < inputs_len; ++i) {
      free(inputs[i]);
    }

    if (!ok) {
      return false;
    }

    if (!cursor_skip_ws(cur)) {
      return false;
    }
    if (cur->offset < cur->len && cur->data[cur->offset] == ',') {
      cur->offset++;
      continue;
    }
    if (cur->offset < cur->len && cur->data[cur->offset] == ']') {
      cur->offset++;
      return true;
    }
  }
}

static bool parse_manifest(uint8_t *bytes, size_t len) {
  cursor_t cur;
  char *field = NULL;
  char *schema = NULL;
  bool ok = false;

  cur.data = bytes;
  cur.len = len;
  cur.offset = 0u;

  if (!cursor_skip_ws(&cur) || cur.offset >= cur.len ||
      cur.data[cur.offset] != '{') {
    return false;
  }
  cur.offset++;

  while (true) {
    if (!cursor_read_string(&cur, &field)) {
      break;
    }
    if (!cursor_skip_ws(&cur) || cur.offset >= cur.len ||
        cur.data[cur.offset] != ':') {
      break;
    }
    cur.offset++;
    if (strcmp(field, "schema") == 0) {
      if (!cursor_read_string(&cur, &schema)) {
        break;
      }
    } else if (strcmp(field, "cases") == 0) {
      if (!parse_manifest_cases(&cur)) {
        break;
      }
    } else {
      break;
    }

    free(field);
    field = NULL;
    if (!cursor_skip_ws(&cur)) {
      break;
    }
    if (cur.offset < cur.len && cur.data[cur.offset] == ',') {
      cur.offset++;
      continue;
    }
    if (cur.offset < cur.len && cur.data[cur.offset] == '}') {
      cur.offset++;
      break;
    }
  }

  if (schema != NULL &&
      strcmp(schema, "amduat.conformance.fps.v0") == 0) {
    ok = true;
  }

  free(field);
  free(schema);
  return ok;
}

int main(void) {
  char path[512];
  uint8_t *bytes = NULL;
  size_t len = 0u;
  int exit_code = 1;

  if (!build_fixture_path(path, sizeof(path))) {
    fprintf(stderr, "fixture path build failed\n");
    return exit_code;
  }
  if (!read_file(path, &bytes, &len)) {
    fprintf(stderr, "fixture read failed: %s\n", path);
    return exit_code;
  }
  if (!parse_manifest(bytes, len)) {
    fprintf(stderr, "fixture parse failed\n");
    goto cleanup;
  }

  exit_code = 0;

cleanup:
  free(bytes);
  return exit_code;
}