/* Batttleship (R) ver 2008-Jun-27
 * written by Joseph Larson
 */
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <time.h>
#include <math.h>

#define PL 0
#define CP 1
#define FULL(x) ((x + (x < 2)) + 1)
#define ADD(a,b) if (!bd[a][b].chit) {t[i].x = a; t[i].y = b; i++;}

typedef struct {
  unsigned int x : 4;
  unsigned int y : 4;
} COORD;

typedef struct {
  unsigned int pship : 3;
  unsigned int chit : 1;
  unsigned int cship : 3;
  unsigned int phit :3;
} GRID;

GRID bd[10][10];
COORD t[51];
char ship_life[2][5];
char *ship_name[5] = {"pt ship", "submarine", "cruser", "battleship", "carrier"};

COORD getloc (void) {
  char input[10];
  COORD loc;

  loc.x = loc.y = input[0] = 0;
  do {
    if (input[0]) printf ("Invalad location, letter first then number : ");
    scanf ("%s", input);
    if (isalpha (input[0]) && (loc.x = atoi (&input[1]))) {
      loc.y = tolower (input[0]) - 'a';
      if (loc.y > 9 || loc.x > 10 || loc.x < 0) loc.x = 0;
    }
  } while (!loc.x);
  loc.x --;
  return loc;
}

void show_board (void) {
  int x, y;

  printf ("%16s\t\t%16s\n_ 1 2 3 4 5 6 7 8 9 10\t\t_ 1 2 3 4 5 6 7 8 9 10"
    ,"R A D A R","F L E E T");
  for (y = 0; y < 10; y++) {
    printf ("\n%c ", y + 'a');
    for (x = 0; x < 10; x++)
      printf ("%c ", (bd[x][y].phit) ? (bd[x][y].cship) ? 'X' : 'o' : '.');
    printf ("\t\t%c ", y + 'a');
    for (x = 0; x < 10; x++)
      printf ("%c ", (bd[x][y].chit) ? (bd[x][y].pship) ? 'X'
      : 'o' : ".12345"[bd[x][y].pship]);
  }
  for (y = 4; y >= 0; y--) {
    printf ("\n %10s : ", ship_name[y]);
    if (ship_life[CP][y]) for(x = 0; x < FULL(y); x++) putchar ('#');
    else printf ("SUNK");
    printf ("\t\t %10s : ", ship_name[y]);
    for (x = 0; x < FULL(y); x++) putchar (".#"[ship_life[PL][y] > x]);
  }
}

int valad_ship (COORD s, COORD e, int c) {
  int check, d, v;
  COORD step;

  check = abs ((s.x + 10 * s.y) - (e.x + 10 * e.y));
  if (check % (FULL(c) - 1)) {
    printf ("\nInvalad location. The %s is only %d long\n"
            "and ships can only be placed vertical or horizontal.\n",
            ship_name[c], FULL(c));
    v = 0;
  } else {
    step.x = step.y = 0;
    if ((check / (FULL(c) - 1)) - 1) step.y = 1;
    else step.x = 1;
    if (s.x > e.x) s.x = e.x;
    if (s.y > e.y) s.y = e.y;
    for (d = 0; d < FULL(c) && v; d++) {
      check = bd[s.x + d * step.x][s.y + d * step.y].pship;
      if (check && check != 7) {
        printf ("\nInvalad location. Ships can not overlap.\n");
        v = 0;
      }
    }
  }
  if (v) for (d = 0; d < FULL(c); d++)
    bd[s.x + d * step.x][s.y + d * step.y].pship = c + 1;
  return v;
}

void player_setup (void) {
  int ship;
  COORD start, end;

  for (ship = 4; ship >= 0; ship--)
    do {
      show_board ();
      printf ("\nEnter start location for your %s : ", ship_name[ship]);
      start = getloc();
      printf ("Enter end location (length %d) : ", FULL(ship));
      end = getloc();
    } while (!valad_ship (start, end, ship));
  show_board ();
}

void auto_setup (int pl) {
  COORD s, step;
  int c, d;

  for (c = 0; c < 5; c++) {
    do {
      s.x = rand() % 10; s.y = rand() % 10;
      step.x = step.y = 0;
      if (rand() < RAND_MAX / 2) {
        step.x = 1;
        if (s.x + FULL(c) > 10) s.x -= FULL(c);
      } else {
        step.y = 1;
        if (s.y + FULL(c) > 10) s.y -= FULL(c);
      }
      for (d = 0; d < FULL(c) &&
      (pl) ? !bd[s.x + d * step.x][s.y + d * step.y].cship
      : !bd[s.x + d * step.x][s.y + d * step.y].pship ; d++);
    } while (d < FULL(c));
    for (d = 0; d < FULL(c); d++)
      if (pl)
        bd[s.x + d * step.x][s.y + d * step.y].cship = c + 1;
      else bd[s.x + d * step.x][s.y + d * step.y].pship = c + 1;
  }
}

void init (void) {
  int c, d;
  char input;

  srand (time (NULL));
  for (c = 0; c < 10; c++)
    for (d = 0; d < 10; d++)
      bd[c][d].pship = bd[c][d].chit = bd[c][d].cship = bd[c][d].phit = 0;
  for (c = 0; c < 5; c++)
    ship_life[PL][c] = ship_life[CP][c] = FULL(c);
  printf ("Battleship (R)\n\nDo you want (A)uto or (M)anual setup ? (a/m) ");
  while (!isalpha (input = getchar()));
  if (tolower (input) == 'm')
    player_setup ();
  else auto_setup (PL);
  auto_setup (CP);
}

int check_for_lose (int player) {
  int c;

  for (c = 0; c < 5 && !ship_life[player][c]; c++);
  return (c == 5);
}

void player_turn (void) {
  COORD shot;
  int ship;

  show_board ();
  printf ("\n\nYour shot coordinates : ");
  shot = getloc ();
  if (bd[shot.x][shot.y].phit)
    printf ("A wasted shot! You already fired there!\n");
  else {
    bd[shot.x][shot.y].phit = 1;
    ship = bd[shot.x][shot.y].cship;
    if (ship) {
      printf ("HIT!\n");
      if (!(--ship_life[CP][--ship]))
        printf ("You sunk my %s.\n",ship_name[ship]);
    } else printf ("Miss.\n");
  }
}

int hit_no_sink (int x, int y) {
  if (bd[x][y].chit) {
    if (bd[x][y].pship == 7) {
      return 1;
    } else if ((bd[x][y].pship) && (ship_life[PL][bd[x][y].pship - 1]))
      return 1;
  }
  return 0;
}

int fill_t (void) {
  COORD c, d;
  int m[5] = {0, 1, 0, -1, 0};
  int x, i = 0;

  for (c.x = 0; c.x < 10; c.x++)
    for (c.y = 0; c.y < 10; c.y++)
      if (hit_no_sink (c.x,c.y)) {
        for (x = 0; x < 4; x++)
          if (c.x + m[x] >= 0 && c.x + m[x] < 10
            && c.y + m[x + 1] >= 0 && c.y + m[x + 1] < 10) {
            if (hit_no_sink (c.x + m[x], c.y + m[x + 1])) {
              d.x = c.x; d.y = c.y;
              while (d.x >= 0 && d.x < 10 && d.y >= 0 && d.y < 10
                && hit_no_sink (d.x, d.y)) {d.x -= m[x]; d.y -= m[x + 1];}
              if (d.x >= 0 && d.x < 10 && d.y >= 0 && d.y < 10) ADD (d.x, d.y);
            }
          }
        if (!i)
          for (x = 0; x < 4; x++)
            if (c.x + m[x] >= 0 && c.x + m[x] < 10
              && c.y + m[x + 1] >= 0 && c.y + m[x + 1] < 10)
              ADD (c.x + m[x], c.y + m[x + 1]);
      }
  if (!i)
    for (c.x = 0; c.x < 10; c.x++)
      for (c.y = 0; c.y < 10; c.y++)
        if ((c.x + c.y) % 2) ADD (c.x, c.y);
  return i;
}

void compy_turn (void) {
  int z, c;

  c = fill_t ();
  z = rand () % c;
  printf ("\nMy shot : %c%d\n", t[z].y + 'a', t[z].x + 1);
  bd[t[z].x][t[z].y].chit = 1;
  c = bd[t[z].x][t[z].y].pship;
  if (c) {
    printf ("HIT!\n");
    if (!(--ship_life[PL][c - 1]))
      printf ("I sunk your %s.\n", ship_name[c - 1]);
  } else printf ("Miss.\n");
}

void play (void) {
  int winner = 0;

  if (rand () < RAND_MAX / 2) {
    printf ("\nYou go first.\n");
    player_turn ();
  } else printf ("\nI'll go first.\n");
  do {
    compy_turn ();
    if (check_for_lose (PL)) {
      winner = 1;
      printf ("\nI win!\n");
    } else {
      player_turn ();
      if (check_for_lose (CP)) {
        winner = 1;
        printf ("\nYou win!\n");
      }
    }
  } while (!winner);
  show_board ();
}

int play_again (void) {
  char input;

  printf ("\nDo you wish to play again? (y/n) ");
  while (!isalpha (input = getchar()));
  if (tolower (input) != 'n') return 1;
  else return 0;
}

int main (void) {
  init ();
  do {play ();} while (play_again ());
  printf ("\nIt's been fun! So long Admiral!\n");
  exit (0);
}