#ifndef MOLECULE_READER_H
#define MOLECULE_READER_H

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

#include <stdbool.h>
#include <stdint.h>

#ifndef MOLECULE_API_DECORATOR
#define __DEFINE_MOLECULE_API_DECORATOR
#define MOLECULE_API_DECORATOR
#endif /* MOLECULE_API_DECORATOR */

#define MOLECULE_API_VERSION 7000
#define MOLECULEC_VERSION_MIN 5000

#if MOLECULE_API_VERSION < MOLECULE_API_VERSION_MIN
#error This file was generated by a newer version of moleculec which is \
    incompatible with current headers in use. Please update the headers.
#endif

#if MOLECULEC_VERSION < MOLECULEC_VERSION_MIN
#error This file was generated by an older version of moleculec which is \
    incompatible with current headers in use. Please regenerate this file \
    with a newer version of moleculec.
#endif

/*
 * This part is not for normal users.
 */

// Test if the host is big endian machine.
#define is_le()       \
  ((union {           \
     uint16_t i;      \
     unsigned char c; \
   }){.i = 1}         \
       .c)

/*
 * Definitions of types and simple utilities.
 */

/* Core types */

typedef uint32_t mol_num_t;  // Item Id

typedef uint8_t mol_errno;  // Error Number

#define MolNum UINT32_C

#define MOL_NUM_T_SIZE 4

// Bytes segment.
typedef struct {
  uint8_t *ptr;    // Pointer
  mol_num_t size;  // Full size
} mol_seg_t;

// Unpacked Union
typedef struct {
  mol_num_t item_id;  // Item Id
  mol_seg_t seg;      // Segment
} mol_union_t;

// Result for returning segment.
typedef struct {
  mol_errno errno;  // Error Number
  mol_seg_t seg;    // Segment
} mol_seg_res_t;

/* Error Numbers */

#define MOL_OK 0x00
#define MOL_ERR 0xff

#define MOL_ERR_TOTAL_SIZE 0x01
#define MOL_ERR_HEADER 0x02
#define MOL_ERR_OFFSET 0x03
#define MOL_ERR_UNKNOWN_ITEM 0x04
#define MOL_ERR_INDEX_OUT_OF_BOUNDS 0x05
#define MOL_ERR_FIELD_COUNT 0x06
#define MOL_ERR_DATA 0x07

/* Utilities. */

MOLECULE_API_DECORATOR mol_num_t mol_unpack_number(const uint8_t *src) {
  uint32_t output = 0;
  uint8_t *dst = (uint8_t *)&output;
  if (is_le()) {
    dst[3] = src[3];
    dst[2] = src[2];
    dst[1] = src[1];
    dst[0] = src[0];
  } else {
    dst[3] = src[0];
    dst[2] = src[1];
    dst[1] = src[2];
    dst[0] = src[3];
  }
  return output;
}

/*
 * Core functions.
 */

/* Verify Functions. */

// Verify Array / Struct.
MOLECULE_API_DECORATOR mol_errno mol_verify_fixed_size(const mol_seg_t *input,
                                                       mol_num_t total_size) {
  return input->size == total_size ? MOL_OK : MOL_ERR_TOTAL_SIZE;
}

// Verify FixVec.
MOLECULE_API_DECORATOR mol_errno mol_fixvec_verify(const mol_seg_t *input,
                                                   mol_num_t item_size) {
  if (input->size < MOL_NUM_T_SIZE) {
    return MOL_ERR_HEADER;
  }
  mol_num_t item_count = mol_unpack_number(input->ptr);
  if (item_count == 0) {
    return input->size == MOL_NUM_T_SIZE ? MOL_OK : MOL_ERR_TOTAL_SIZE;
  }
  mol_num_t total_size = MOL_NUM_T_SIZE + item_size * item_count;
  return input->size == total_size ? MOL_OK : MOL_ERR_TOTAL_SIZE;
}

/* Getters.
 *
 * ### Notice
 *
 * The input of getters should be checked.
 *
 * These getters will raise segmentation fault if the input is illegal or
 * return an incorrect result.
 */

// Check if an Option is None.
MOLECULE_API_DECORATOR bool mol_option_is_none(const mol_seg_t *input) {
  return input->size == 0;
}

// Get the inner of a Union.
MOLECULE_API_DECORATOR mol_union_t mol_union_unpack(const mol_seg_t *input) {
  mol_union_t ret;
  ret.item_id = mol_unpack_number(input->ptr);
  ret.seg.ptr = input->ptr + MOL_NUM_T_SIZE;
  ret.seg.size = input->size - MOL_NUM_T_SIZE;
  return ret;
}

// Get the length of a FixVec.
MOLECULE_API_DECORATOR mol_num_t mol_fixvec_length(const mol_seg_t *input) {
  return mol_unpack_number(input->ptr);
}

// Get the length of a DynVec.
MOLECULE_API_DECORATOR mol_num_t mol_dynvec_length(const mol_seg_t *input) {
  if (input->size == MOL_NUM_T_SIZE) {
    return 0;
  } else {
    return (mol_unpack_number(input->ptr + MOL_NUM_T_SIZE) / 4) - 1;
  }
}

// Get the actual field count of a Table.
MOLECULE_API_DECORATOR mol_num_t
mol_table_actual_field_count(const mol_seg_t *input) {
  return mol_dynvec_length(input);
}

// If a Table has extra fields.
MOLECULE_API_DECORATOR bool mol_table_has_extra_fields(const mol_seg_t *input,
                                                       mol_num_t field_count) {
  return mol_table_actual_field_count(input) > field_count;
}

// Slice a segment for Array / Struct by offset.
MOLECULE_API_DECORATOR mol_seg_t mol_slice_by_offset(const mol_seg_t *input,
                                                     mol_num_t offset,
                                                     mol_num_t size) {
  mol_seg_t seg;
  seg.ptr = input->ptr + offset;
  seg.size = size;
  return seg;
}

// Slice a segment for FixVec by index.
MOLECULE_API_DECORATOR mol_seg_res_t mol_fixvec_slice_by_index(
    const mol_seg_t *input, mol_num_t item_size, mol_num_t item_index) {
  mol_seg_res_t res;
  mol_num_t item_count = mol_unpack_number(input->ptr);
  if (item_index >= item_count) {
    res.errno = MOL_ERR_INDEX_OUT_OF_BOUNDS;
  } else {
    res.errno = MOL_OK;
    res.seg.ptr = input->ptr + MOL_NUM_T_SIZE + item_size * item_index;
    res.seg.size = item_size;
  }
  return res;
}

// Slice a segment for DynVec by index.
MOLECULE_API_DECORATOR mol_seg_res_t
mol_dynvec_slice_by_index(const mol_seg_t *input, mol_num_t item_index) {
  mol_seg_res_t res;
  mol_num_t total_size = mol_unpack_number(input->ptr);
  if (total_size == MOL_NUM_T_SIZE) {
    res.errno = MOL_ERR_INDEX_OUT_OF_BOUNDS;
  } else {
    mol_num_t item_count =
        (mol_unpack_number(input->ptr + MOL_NUM_T_SIZE) / 4) - 1;
    if (item_index >= item_count) {
      res.errno = MOL_ERR_INDEX_OUT_OF_BOUNDS;
    } else {
      mol_num_t item_start =
          mol_unpack_number(input->ptr + MOL_NUM_T_SIZE * (item_index + 1));
      if (item_index + 1 == item_count) {
        res.errno = MOL_OK;
        res.seg.ptr = input->ptr + item_start;
        res.seg.size = total_size - item_start;
      } else {
        mol_num_t item_end =
            mol_unpack_number(input->ptr + MOL_NUM_T_SIZE * (item_index + 2));
        res.errno = MOL_OK;
        res.seg.ptr = input->ptr + item_start;
        res.seg.size = item_end - item_start;
      }
    }
  }
  return res;
}

// Slice a segment for Table by index.
MOLECULE_API_DECORATOR mol_seg_t
mol_table_slice_by_index(const mol_seg_t *input, mol_num_t field_index) {
  mol_seg_res_t res = mol_dynvec_slice_by_index(input, field_index);
  return res.seg;
}

// Slice the raw bytes from a `vector <byte>` (FixVec, with a header).
MOLECULE_API_DECORATOR mol_seg_t
mol_fixvec_slice_raw_bytes(const mol_seg_t *input) {
  mol_seg_t seg;
  seg.ptr = input->ptr + MOL_NUM_T_SIZE;
  seg.size = mol_unpack_number(input->ptr);
  return seg;
}

/*
 * Undef macros which are internal use only.
 */

#undef is_le

#ifdef __DEFINE_MOLECULE_API_DECORATOR
#undef MOLECULE_API_DECORATOR
#undef __DEFINE_MOLECULE_API_DECORATOR
#endif /* __DEFINE_MOLECULE_API_DECORATOR */

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* MOLECULE_READER_H */