// bin.h - flat file, fixed block size, time series database
//
// Thread safety: Not thread-safe. External synchronization required.
// Behavior: No input validation — out-of-order data persists as-is.
//   Unbuffered I/O by default (use _buffered variants for performance).
//   _ok variants return 1 on success, 0 on any error (invalid args, I/O fail,
//   overflow). Non-_ok variants remain for backward compatibility.

#ifndef BIN_H
#define BIN_H

/* USER-DEFINED (define before including):
 *   typedef <numerical_type> bin_key_t;
 */

#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#include "type.h"

typedef struct {
  u64 length;
  u64 block_size;
} bin_meta_t;

FILE *bin_init(char const *, u64);
FILE *bin_init_buffered(char const *, u64);
FILE *bin_open(char const *path);
FILE *bin_open_buffered(char const *path);
int bin_read(FILE *, i64, void *, u64);
void bin_write(FILE *, i64, void *, u64);
int bin_write_ok(FILE *, i64, void *, u64);
void bin_insert(FILE *, i64, void *, u64);
int bin_insert_ok(FILE *, i64, void *, u64);
void bin_append(FILE *, void *, u64);
int bin_append_ok(FILE *, void *, u64);
int bin_close(FILE *);

u64 bin_length(FILE *);
u64 bin_block_size(FILE *);

i64 bin_search(FILE *, bin_key_t);
u64 bin_fuzzy_index(i64);

#endif // BIN_H

#ifdef BIN_IMPLEMENTATION // IMPLEMENTATION

#include <stdlib.h>

static void bin_write_length(FILE *, u64);
static void bin_write_block_size(FILE *, u64);

static inline i64 index_bytes_safe(i64 i, u64 bs, u64 *out) {
  if (bs == 0 || i < 0 || (u64)i > (UINT64_MAX - sizeof(bin_meta_t)) / bs)
    return -1;
  *out = (u64)i * bs + sizeof(bin_meta_t);
  return 0;
}

#define member_sizeof(type, member) (sizeof(((type *)0)->member))

static inline int fseek_safe(FILE *f, u64 offset) {
#ifdef _WIN32
  return _fseeki64(f, (long long)offset, SEEK_SET);
#else
  if ((u64)(long)offset != offset)
    return -1;
  return fseek(f, (long)offset, SEEK_SET);
#endif
}

// bin_init()
//
// Creates the desired binary file
//
// path - The path and file name for the desired file
//
// return - The newly created file

FILE *bin_init(char const *path, u64 block_size) {
  if (!path)
    return NULL;
  FILE *f = fopen(path, "wb+");

  if (!f)
    return NULL;

  setvbuf(f, NULL, _IONBF, 0);

  bin_write_length(f, 0);
  bin_write_block_size(f, block_size);

  return f;
}

FILE *bin_init_buffered(char const *path, u64 block_size) {
  if (!path)
    return NULL;
  FILE *f = fopen(path, "wb+");

  if (!f)
    return NULL;

  bin_write_length(f, 0);
  bin_write_block_size(f, block_size);

  return f;
}

// bin_open()
//
// Opens the desired binary file
//
// path - The path and file name for the desired file
//
// return - The newly opened file

FILE *bin_open(char const *path) {
  if (!path)
    return NULL;
  FILE *f = fopen(path, "rb+");

  if (!f)
    return NULL;

  setvbuf(f, NULL, _IONBF, 0);

  return f;
}

FILE *bin_open_buffered(char const *path) {
  if (!path)
    return NULL;
  return fopen(path, "rb+");
}

// bin_close()
//
// Closes the desired binary file
//
// f - The file descriptor to be closed

int bin_close(FILE *f) {
  if (!f) return 0;
  int r = fclose(f);
  return r == 0;
}

// bin_read()
//
// Read the desired data into the buffer
//
// f - The file pointer
// i - The initial index of the read
// data - The block_t buffer to be read into
// n - The number of elements to read into the buffer

int bin_read(FILE *f, i64 i, void *data, u64 n) {
  if (!f || !data || n == 0)
    return 0;
  u64 bs = bin_block_size(f);
  if (bs == 0)
    return 0;

  if (i < 0)
    return 0;
  u64 len = bin_length(f);
  if ((u64)i + n > len)
    return 0;

  u64 offset = 0;
  if (index_bytes_safe(i, bs, &offset) != 0)
    return 0;
  if (bs > SIZE_MAX / n)
    return 0;
  fseek_safe(f, offset);
  size_t read_n = fread(data, (size_t)bs, (size_t)n, f);
  if (read_n != n) {
    if ((n - read_n) > SIZE_MAX / bs)
      return (int)read_n;
    memset((char *)data + read_n * bs, 0, (n - read_n) * bs);
    return (int)read_n;
  }
  return (int)n;
}

// bin_write()
//
// Write the buffer into the file
//
// f - The file pointer
// i - The initial index of the write
// data - The block_t buffer to write from
// n - The number of elements to write from the buffer

void bin_write(FILE *f, i64 i, void *data, u64 n) {
  (void)bin_write_ok(f, i, data, n);
}

int bin_write_ok(FILE *f, i64 i, void *data, u64 n) {
  if (!f || !data || n == 0)
    return 0;
  u64 l = bin_length(f);
  u64 bs = bin_block_size(f);
  if (bs == 0)
    return 0;

  if (i < 0)
    return 0;
  if ((u64)i + n > l)
    return 0;

  u64 offset = 0;
  if (index_bytes_safe(i, bs, &offset) != 0)
    return 0;
  if (fseek_safe(f, offset) != 0)
    return 0;
  size_t written = fwrite(data, bs, n, f);
  return written == (size_t)n;
}

// bin_append()
//
// Appends the given data to the end of the binary file
//
// f - The file to be appended to
// data - The blocks to append to the file
// n - The number of block to be appended

void bin_append(FILE *f, void *data, u64 n) {
  (void)bin_append_ok(f, data, n);
}

int bin_append_ok(FILE *f, void *data, u64 n) {
  if (!f || !data || n == 0)
    return 0;
  u64 l = bin_length(f);
  u64 bs = bin_block_size(f);
  if (bs == 0)
    return 0;

  if (l > UINT64_MAX - n)
    return 0;

  u64 offset = 0;
  if (index_bytes_safe((i64)l, bs, &offset) != 0)
    return 0;
  if (fseek_safe(f, offset) != 0)
    return 0;
  size_t written = fwrite(data, bs, n, f);
  if (written != (size_t)n)
    return 0;
  bin_write_length(f, l + n);
  return 1;
}

// bin_insert()
//
// Inserts the given data into the binary file
//
// f - The file to be inserted into
// i - The initial index of the insertion
// data - The blocks to insert into the file
// n - The number of blocks to be inserted

void bin_insert(FILE *f, i64 i, void *data, u64 n) {
  (void)bin_insert_ok(f, i, data, n);
}

int bin_insert_ok(FILE *f, i64 i, void *data, u64 n) {
  if (!f || !data || n == 0)
    return 0;
  u64 l = bin_length(f);
  u64 bs = bin_block_size(f);
  if (bs == 0)
    return 0;

  if (i < 0 || (u64)i > l)
    return 0;

  u64 blocks_to_move = l - (u64)i;
  if (blocks_to_move > UINT64_MAX / bs)
    return 0;

  if (l > UINT64_MAX - n)
    return 0;

  u64 offset = 0;
  if (index_bytes_safe(i, bs, &offset) != 0)
    return 0;
  if (fseek_safe(f, offset) != 0)
    return 0;

  if (blocks_to_move > 0) {
    u64 tmp_n = blocks_to_move * bs;
    if (tmp_n > SIZE_MAX)
      return 0;
    u8 *tmp = malloc((size_t)tmp_n);
    if (tmp == NULL)
      return 0;

    size_t rn = fread(tmp, (size_t)bs, (size_t)blocks_to_move, f);
    if (rn != (size_t)blocks_to_move) {
      memset((char *)tmp + rn * (size_t)bs, 0, ((size_t)blocks_to_move - rn) * (size_t)bs);
    }

    if (fseek_safe(f, offset) != 0) { free(tmp); return 0; }
    size_t written = fwrite(data, bs, n, f);
    if (written != (size_t)n) { free(tmp); return 0; }
    fwrite(tmp, 1, (size_t)tmp_n, f);
    free(tmp);
  } else {
    size_t written = fwrite(data, bs, n, f);
    if (written != (size_t)n)
      return 0;
  }
  bin_write_length(f, l + n);
  return 1;
}

// bin_length()
//
// Reads the block count number from the given file
//
// f - The file to be read from
//
// return - The length / number of entries in the file

u64 bin_length(FILE *f) {
  if (!f) return 0;
  u64 n = 0;

  fseek(f, offsetof(bin_meta_t, length), SEEK_SET);
  size_t rn = fread(&n, member_sizeof(bin_meta_t, length), 1, f);
  if (rn != 1) return 0;

  return n;
}

// bin_block_size()
//
// Reads the block size from the given file
//
// f - The file to be read from
//
// return - The block size for the entries in the file

u64 bin_block_size(FILE *f) {
  if (!f) return 0;
  u64 n = 0;

  fseek(f, offsetof(bin_meta_t, block_size), SEEK_SET);
  size_t rn = fread(&n, member_sizeof(bin_meta_t, block_size), 1, f);
  if (rn != 1) return 0;

  return n;
}

// bin_search()
//
// Search for a given key in the file
//
// f - The file to be searched within
// k - The key to search for
//
// return - The block_t index of the key. In the case that the key is not found,
//          The returned value is -( index + 1 ) where index is that of the
//          first element greater than k or bin_length().

i64 bin_search(FILE *f, bin_key_t k) {
  if (!f) return -1;
  fpos_t origin;
  fgetpos(f, &origin);

  u64 len = bin_length(f);
  if (len == 0) {
    fsetpos(f, &origin);
    return -1;
  }

  i64 l = 0;
  i64 r = (i64)len - 1;
  i64 m;

  u64 bs = bin_block_size(f);

  bin_key_t key = 0;
  int found = 0;

  while (l <= r) {
    m = l + (r - l) / 2;
    u64 offset = 0;
    if (index_bytes_safe(m, bs, &offset) != 0) {
      fsetpos(f, &origin);
      return -(l + 1);
    }
    fseek_safe(f, offset);
    if (fread(&key, sizeof(k), 1, f) != 1) {
      fsetpos(f, &origin);
      return -(l + 1);
    }

    if (key < k)
      l = m + 1;

    else if (key > k)
      r = m - 1;

    else {
      found = 1;
      break;
    }
  }

  fsetpos(f, &origin);

  if (!found)
    return -(l + 1);

  return m;
}

// bin_fuzzy_index()
//
// If one does a binary search on the file and is returned a negative error,
// it may be useful to retrueve the index which it would be at.
//
// i - The number to map to the correct index
//
// return - The index remapped the binary file. If the index is already
// positive, then no operation occurrs.

u64 bin_fuzzy_index(i64 i) {
  if (i < 0)
    return (u64)(-(i + 1));
  return (u64)i;
}

// bin_write_length()
//
// Writes a length to the given file
//
// f - The file to be written to
// count - The length to be written to the file

static void bin_write_length(FILE *f, u64 length) {
  fseek(f, offsetof(bin_meta_t, length), SEEK_SET);
  if (fwrite(&length, member_sizeof(bin_meta_t, length), 1, f) != 1) {
    clearerr(f);
  }
}

// bin_write_block_size()
//
// Writes a block size to the given file
//
// f - The file to be written to
// count - The block size to be written to the file

static void bin_write_block_size(FILE *f, u64 block_size) {
  fseek(f, offsetof(bin_meta_t, block_size), SEEK_SET);
  fwrite(&block_size, member_sizeof(bin_meta_t, block_size), 1, f);
}

#endif