#include "cmd.h"
#include <string.h>

#define CMD_TABLE_SIZE 4

typedef struct {
  const char *name;
  cmd_fn_t fn;
} cmd_entry_t;

static cmd_entry_t table[CMD_TABLE_SIZE];
static cmd_write_fn write_fn;

static uint32_t djb2(const char *str) {
  uint32_t hash = 5381;
  unsigned char c;
  while ((c = (unsigned char)*str++))
    hash = ((hash << 5) + hash) + c;
  return hash;
}

void cmd_init(cmd_write_fn fn) {
  write_fn = fn;
  memset(table, 0, sizeof(table));
}

void cmd_register(const char *name, cmd_fn_t fn) {
  uint32_t idx = djb2(name) & (CMD_TABLE_SIZE - 1);
  for (int i = 0; i < CMD_TABLE_SIZE; i++) {
    uint32_t slot = (idx + (uint32_t)i) & (CMD_TABLE_SIZE - 1);
    if (table[slot].name == NULL) {
      table[slot].name = name;
      table[slot].fn = fn;
      return;
    }
  }
  while (1) {} // table full
}

void cmd_dispatch(char *line) {
  char *argv[8];
  int argc = 0;

  char *tok = strtok(line, " \t");
  while (tok != NULL && argc < 8) {
    argv[argc++] = tok;
    tok = strtok(NULL, " \t");
  }

  if (argc == 0) return;

  uint32_t idx = djb2(argv[0]) & (CMD_TABLE_SIZE - 1);
  for (int i = 0; i < CMD_TABLE_SIZE; i++) {
    uint32_t slot = (idx + (uint32_t)i) & (CMD_TABLE_SIZE - 1);
    if (table[slot].name == NULL) break;
    if (strcmp(table[slot].name, argv[0]) == 0) {
      table[slot].fn(argc, argv);
      return;
    }
  }

  if (write_fn) {
    write_fn((const uint8_t *)"unknown command\r\n", 17);
  }
}