/*-
 * bs.c - original author: Bruce Holloway
 *              salvo option by: Chuck A DeGaul
 * with improved user interface, autoconfiguration and code cleanup
 *              by Eric S. Raymond <esr@snark.thyrsus.com>
 * v1.2 with color support and minor portability fixes, November 1990
 * v2.0 featuring strict ANSI/POSIX conformance, November 1993.
 *
 * $FreeBSD: src/games/bs/bs.c,v 1.9 2000/02/21 03:07:31 billf Exp $
 */

#include <assert.h>
#include <ctype.h>
#include <ncurses.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

/*
 * Constants for tuning the random-fire algorithm. It prefers moves that
 * diagonal-stripe the board with a stripe separation of srchstep. If
 * no such preferred moves are found, srchstep is decremented.
 */
#define BEGINSTEP       3       /* initial value of srchstep */

/* miscellaneous constants */
#define SHIPTYPES       5
#define OTHER           (1-turn)
#define PLAYER          0
#define COMPUTER        1
#define MARK_HIT        'H'
#define MARK_MISS       'o'
#define CTRLC           '\003'  /* used as terminate command */
#define FF              '\014'  /* used as redraw command */

/* coordinate handling */
#define BWIDTH          10
#define BDEPTH          10

/* display symbols */
#define SHOWHIT         '*'
#define SHOWSPLASH      ' '
#define IS_SHIP(c)      isupper(c)

/* how to position us on player board */
#define PYBASE  3
#define PXBASE  3
#define PY(y)   (PYBASE + (y))
#define PX(x)   (PXBASE + (x)*3)
#define pgoto(y, x)     move(PY(y), PX(x))

/* how to position us on cpu board */
#define CYBASE  3
#define CXBASE  48
#define CY(y)   (CYBASE + (y))
#define CX(x)   (CXBASE + (x)*3)
#define cgoto(y, x)     move(CY(y), CX(x))

#define ONBOARD(x, y)   (x >= 0 && x < BWIDTH && y >= 0 && y < BDEPTH)

/* other board locations */
#define COLWIDTH        80
#define PROMPTLINE      21                      /* prompt line */
#define SYBASE          CYBASE + BDEPTH + 3     /* move key diagram */
#define SXBASE          63
#define MYBASE          SYBASE - 1              /* diagram caption */
#define MXBASE          64
#define HYBASE          SYBASE - 1              /* help area */
#define HXBASE          0

/* this will need to be changed if BWIDTH changes */
static char numbers[] = "   0  1  2  3  4  5  6  7  8  9";

static char carrier[] = "Aircraft Carrier";
static char battle[] = "Battleship";
static char sub[] = "Submarine";
static char destroy[] = "Destroyer";
static char ptboat[] = "PT Boat";

static char name[40];
static char dftname[] = "stranger";

/* direction constants */
enum directions { E, SE, S, SW, W, NW, N, NE };
static int xincr[8] = {1,  1,  0, -1, -1, -1,  0,  1};
static int yincr[8] = {0,  1,  1,  1,  0, -1, -1, -1};

/* current ship position and direction */
static int curx = (BWIDTH / 2);
static int cury = (BDEPTH / 2);

typedef struct {
    char *name;                         /* name of the ship type */
    char hits;                          /* how many times has this ship been hit? */
    char symbol;                        /* symbol for game purposes */
    char length;                        /* length of ship */
    char x, y;                          /* coordinates of ship start point */
    enum directions dir;        /* direction of `bow' */
    bool placed;                        /* has it been placed on the board? */
}
ship_t;

static ship_t plyship[SHIPTYPES] =
{
    { carrier,  0, 'A', 5, 0, 0, E, FALSE},
    { battle,   0, 'B', 4, 0, 0, E, FALSE},
    { destroy,  0, 'D', 3, 0, 0, E, FALSE},
    { sub,      0, 'S', 3, 0, 0, E, FALSE},
    { ptboat,   0, 'P', 2, 0, 0, E, FALSE},
};

static ship_t cpuship[SHIPTYPES] =
{
    { carrier,  0, 'A', 5, 0, 0, E, FALSE},
    { battle,   0, 'B', 4, 0, 0, E, FALSE},
    { destroy,  0, 'D', 3, 0, 0, E, FALSE},
    { sub,      0, 'S', 3, 0, 0, E, FALSE},
    { ptboat,   0, 'P', 2, 0, 0, E, FALSE},
};

/* "Hits" board, and main board. */
static char hits[2][BWIDTH][BDEPTH], board[2][BWIDTH][BDEPTH];

static int turn;                        /* 0=player, 1=computer */
static int plywon=0, cpuwon=0;          /* How many games has each won? */

static int salvo, blitz, closepack;

#define PR      addstr

static void prompt(int, const char *, ...) __printflike(2, 3);
static bool checkplace (int, ship_t *, int);
static int getcoord (int);
int playagain (void);

/* end the game, either normally or due to signal */
static void
uninitgame(void)
{
    clear();
    refresh();
    resetterm();
    echo();
    endwin();
    exit(0);
}

static void
sighandler(__unused int sig)
{
        uninitgame();
}

/* announce which game options are enabled */
static void
announceopts(void)
{
    printw("Playing %s game (", (salvo || blitz || closepack) ?
                        "optional" : "standard");

        if (salvo)
            printw("salvo, ");
        else
            printw("nosalvo, ");

        if (blitz)
            printw("blitz, ");
        else
            printw("noblitz, ");

        if (closepack)
            printw("closepack)");
        else
            printw("noclosepack)");
}

static void
intro(void)
{
    char *tmpname;

    srandomdev();

    tmpname = getlogin();
    signal(SIGINT,sighandler);
    signal(SIGINT,sighandler);
    signal(SIGIOT,sighandler);          /* for assert(3) */
    if(signal(SIGQUIT,SIG_IGN) != SIG_IGN)
                signal(SIGQUIT,sighandler);

    if(tmpname != NULL) {
                strcpy(name,tmpname);
                name[0] = toupper(name[0]);
    } else {
                strcpy(name,dftname);
        }

    initscr();
#ifdef KEY_MIN
    keypad(stdscr, TRUE);
#endif /* KEY_MIN */
    saveterm();
    nonl();
    cbreak();
    noecho();

#ifdef PENGUIN
    clear();
    mvaddstr(4,29,"Welcome to Battleship!");
    move(8,0);
    PR("                                                  \\\n");
    PR("                           \\                     \\ \\\n");
    PR("                          \\ \\                   \\ \\ \\_____________\n");
    PR("                         \\ \\ \\_____________      \\ \\/            |\n");
    PR("                          \\ \\/             \\      \\/             |\n");
    PR("                           \\/               \\_____/              |__\n");
    PR("           ________________/                                       |\n");
    PR("           \\  S.S. Penguin                                         |\n");
    PR("            \\                                                     /\n");
    PR("             \\___________________________________________________/\n");

    mvaddstr(22,27,"Hit any key to continue..."); refresh();
    getch();
#endif /* PENGUIN */

#ifdef A_COLOR
    start_color();

    init_pair(COLOR_BLACK, COLOR_BLACK, COLOR_BLACK);
    init_pair(COLOR_GREEN, COLOR_GREEN, COLOR_BLACK);
    init_pair(COLOR_RED, COLOR_RED, COLOR_BLACK);
    init_pair(COLOR_CYAN, COLOR_CYAN, COLOR_BLACK);
    init_pair(COLOR_WHITE, COLOR_WHITE, COLOR_BLACK);
    init_pair(COLOR_MAGENTA, COLOR_MAGENTA, COLOR_BLACK);
    init_pair(COLOR_BLUE, COLOR_BLUE, COLOR_BLACK);
    init_pair(COLOR_YELLOW, COLOR_YELLOW, COLOR_BLACK);
#endif /* A_COLOR */

}

/* print a message at the prompt line */
static void
prompt(int n, const char *f, ...)
{
    char buf[COLWIDTH + 1];
    va_list ap;

    va_start(ap, f);
    move(PROMPTLINE + n, 0);
    clrtoeol();
    vsnprintf(buf, COLWIDTH + 1, f, ap);
    printw("%s", buf);
    refresh();
    va_end(ap);
}

static void
error(const char *s)
{
    move(PROMPTLINE + 2, 0);
    clrtoeol();
    if (s) {
                addstr(s);
                beep();
    }
}

static void
placeship(int b, ship_t *ss, int vis)
{
    int l;

    for(l = 0; l < ss->length; ++l) {
                int newx = ss->x + l * xincr[ss->dir];
                int newy = ss->y + l * yincr[ss->dir];

                board[b][newx][newy] = ss->symbol;
                if (vis) {
                pgoto(newy, newx);
                addch((chtype)ss->symbol);
                }
    }
    ss->hits = 0;
}

static int
rnd(int n)
{
    return(random() % n);
}

/* generate a valid random ship placement into px,py */
static void
randomplace(int b, ship_t *ss)
{
    do {
                ss->y = rnd(BDEPTH);
                ss->x = rnd(BWIDTH);
                ss->dir = rnd(2) ? E : S;
    } while (!checkplace(b, ss, FALSE));
}

static void
initgame(void)
{
    int i, j, unplaced;
    ship_t *ss;

    clear();
    mvaddstr(0,35,"BATTLESHIPS");
    move(PROMPTLINE + 2, 0);
    announceopts();

    bzero(board, sizeof(char) * BWIDTH * BDEPTH * 2);
    bzero(hits, sizeof(char) * BWIDTH * BDEPTH * 2);
    for (i = 0; i < SHIPTYPES; i++) {
                ss = cpuship + i;
                ss->x = ss->y = ss->dir = ss->hits = ss->placed = 0;
                ss = plyship + i;
                ss->x = ss->y = ss->dir = ss->hits = ss->placed = 0;
    }

    /* draw empty boards */
    mvaddstr(PYBASE - 2, PXBASE + 5, "Main Board");
    mvaddstr(PYBASE - 1, PXBASE - 3,numbers);
    for(i=0; i < BDEPTH; ++i)
    {
        mvaddch(PYBASE + i, PXBASE - 3, i + 'A');
#ifdef A_COLOR
        if (has_colors())
            attron(COLOR_PAIR(COLOR_BLUE));
#endif /* A_COLOR */
        addch(' ');
        for (j = 0; j < BWIDTH; j++)
            addstr(" . ");
#ifdef A_COLOR
        attrset(0);
#endif /* A_COLOR */
        addch(' ');
        addch(i + 'A');
    }
    mvaddstr(PYBASE + BDEPTH, PXBASE - 3,numbers);
    mvaddstr(CYBASE - 2, CXBASE + 7,"Hit/Miss Board");
    mvaddstr(CYBASE - 1, CXBASE - 3, numbers);
    for(i=0; i < BDEPTH; ++i)
    {
        mvaddch(CYBASE + i, CXBASE - 3, i + 'A');
#ifdef A_COLOR
        if (has_colors())
            attron(COLOR_PAIR(COLOR_BLUE));
#endif /* A_COLOR */
        addch(' ');
        for (j = 0; j < BWIDTH; j++)
            addstr(" . ");
#ifdef A_COLOR
        attrset(0);
#endif /* A_COLOR */
        addch(' ');
        addch(i + 'A');
    }

    mvaddstr(CYBASE + BDEPTH,CXBASE - 3,numbers);

    mvprintw(HYBASE,  HXBASE,
                    "To position your ships: move the cursor to a spot, then");
    mvprintw(HYBASE+1,HXBASE,
                    "type the first letter of a ship type to select it, then");
    mvprintw(HYBASE+2,HXBASE,
                    "type a direction ([hjkl] or [4862]), indicating how the");
    mvprintw(HYBASE+3,HXBASE,
                    "ship should be pointed. You may also type a ship letter");
    mvprintw(HYBASE+4,HXBASE,
                    "followed by `r' to position it randomly, or type `R' to");
    mvprintw(HYBASE+5,HXBASE,
                    "place all remaining ships randomly.");

    mvaddstr(MYBASE,   MXBASE, "Aiming keys:");
    mvaddstr(SYBASE,   SXBASE, "y k u    7 8 9");
    mvaddstr(SYBASE+1, SXBASE, " \\|/      \\|/ ");
    mvaddstr(SYBASE+2, SXBASE, "h-+-l    4-+-6");
    mvaddstr(SYBASE+3, SXBASE, " /|\\      /|\\ ");
    mvaddstr(SYBASE+4, SXBASE, "b j n    1 2 3");

    /* have the computer place ships */
    for(ss = cpuship; ss < cpuship + SHIPTYPES; ss++)
    {
        randomplace(COMPUTER, ss);
        placeship(COMPUTER, ss, FALSE);
    }

    ss = NULL;
    do {
        char c, docked[SHIPTYPES + 2], *cp = docked;

        /* figure which ships still wait to be placed */
        *cp++ = 'R';
        for (i = 0; i < SHIPTYPES; i++)
            if (!plyship[i].placed)
                *cp++ = plyship[i].symbol;
        *cp = '\0';

        /* get a command letter */
        prompt(1, "Type one of [%s] to pick a ship.", docked+1);
        do {
            c = getcoord(PLAYER);
        } while
            (!strchr(docked, c));

        if (c == 'R')
            ungetch('R');
        else
        {
            /* map that into the corresponding symbol */
            for (ss = plyship; ss < plyship + SHIPTYPES; ss++)
                if (ss->symbol == c)
                    break;

            prompt(1, "Type one of [hjklrR] to place your %s.", ss->name);
            pgoto(cury, curx);
        }

        do {
            c = getch();
        } while
            (!strchr("hjklrR", c) || c == FF);

        if (c == FF)
        {
            clearok(stdscr, TRUE);
            refresh();
        }
        else if (c == 'r')
        {
            prompt(1, "Random-placing your %s", ss->name);
            randomplace(PLAYER, ss);
            placeship(PLAYER, ss, TRUE);
            error(NULL);
            ss->placed = TRUE;
        }
        else if (c == 'R')
        {
            prompt(1, "Placing the rest of your fleet at random...");
            for (ss = plyship; ss < plyship + SHIPTYPES; ss++)
                if (!ss->placed)
                {
                    randomplace(PLAYER, ss);
                    placeship(PLAYER, ss, TRUE);
                    ss->placed = TRUE;
                }
            error(NULL);
        }
        else if (strchr("hjkl8462", c))
        {
            ss->x = curx;
            ss->y = cury;

            switch(c)
            {
            case 'k': case '8': ss->dir = N; break;
            case 'j': case '2': ss->dir = S; break;
            case 'h': case '4': ss->dir = W; break;
            case 'l': case '6': ss->dir = E; break;
            }

            if (checkplace(PLAYER, ss, TRUE))
            {
                placeship(PLAYER, ss, TRUE);
                error(NULL);
                ss->placed = TRUE;
            }
        }

        for (unplaced = i = 0; i < SHIPTYPES; i++)
            unplaced += !plyship[i].placed;
    } while
        (unplaced);

    turn = rnd(2);

    mvprintw(HYBASE,  HXBASE,
                    "To fire, move the cursor to your chosen aiming point   ");
    mvprintw(HYBASE+1,  HXBASE,
                    "and strike any key other than a motion key.            ");
    mvprintw(HYBASE+2,  HXBASE,
                    "                                                       ");
    mvprintw(HYBASE+3,  HXBASE,
                    "                                                       ");
    mvprintw(HYBASE+4,  HXBASE,
                    "                                                       ");
    mvprintw(HYBASE+5,  HXBASE,
                    "                                                       ");

    prompt(0, "Press any key to start...");
    getch();
}

static int
getcoord(int atcpu)
{
    int ny, nx, c;

    if (atcpu)
        cgoto(cury,curx);
    else
        pgoto(cury, curx);
    refresh();
    for (;;)
    {
        if (atcpu)
        {
            mvprintw(CYBASE + BDEPTH+1, CXBASE+11, "(%d, %c)", curx, 'A'+cury);
            cgoto(cury, curx);
        }
        else
        {
            mvprintw(PYBASE + BDEPTH+1, PXBASE+11, "(%d, %c)", curx, 'A'+cury);
            pgoto(cury, curx);
        }

        switch(c = getch())
        {
        case 'k': case '8':
#ifdef KEY_MIN
        case KEY_UP:
#endif /* KEY_MIN */
            ny = cury+BDEPTH-1; nx = curx;
            break;
        case 'j': case '2':
#ifdef KEY_MIN
        case KEY_DOWN:
#endif /* KEY_MIN */
            ny = cury+1;        nx = curx;
            break;
        case 'h': case '4':
#ifdef KEY_MIN
        case KEY_LEFT:
#endif /* KEY_MIN */
            ny = cury;          nx = curx+BWIDTH-1;
            break;
        case 'l': case '6':
#ifdef KEY_MIN
        case KEY_RIGHT:
#endif /* KEY_MIN */
            ny = cury;          nx = curx+1;
            break;
        case 'y': case '7':
#ifdef KEY_MIN
        case KEY_A1:
#endif /* KEY_MIN */
            ny = cury+BDEPTH-1; nx = curx+BWIDTH-1;
            break;
        case 'b': case '1':
#ifdef KEY_MIN
        case KEY_C1:
#endif /* KEY_MIN */
            ny = cury+1;        nx = curx+BWIDTH-1;
            break;
        case 'u': case '9':
#ifdef KEY_MIN
        case KEY_A3:
#endif /* KEY_MIN */
            ny = cury+BDEPTH-1; nx = curx+1;
            break;
        case 'n': case '3':
#ifdef KEY_MIN
        case KEY_C3:
#endif /* KEY_MIN */
            ny = cury+1;        nx = curx+1;
            break;
        case FF:
            nx = curx; ny = cury;
            clearok(stdscr, TRUE);
            refresh();
            break;
        default:
            if (atcpu)
                mvaddstr(CYBASE + BDEPTH + 1, CXBASE + 11, "      ");
            else
                mvaddstr(PYBASE + BDEPTH + 1, PXBASE + 11, "      ");
            return(c);
        }

        curx = nx % BWIDTH;
        cury = ny % BDEPTH;
    }
}

/* is this location on the selected zboard adjacent to a ship? */
static int
collidecheck(int b, int y, int x)
{
    int collide;

    /* anything on the square */
    if ((collide = IS_SHIP(board[b][x][y])) != 0)
                return(collide);

    /* anything on the neighbors */
    if (!closepack) {
                int i;

                for (i = 0; i < 8; i++) {
                int xend, yend;

                yend = y + yincr[i];
                xend = x + xincr[i];
                if (ONBOARD(xend, yend))
                        collide += IS_SHIP(board[b][xend][yend]);
                }
        }

    return(collide);
}

static bool
checkplace(int b, ship_t *ss, int vis)
{
    int l, xend, yend;

    /* first, check for board edges */
    xend = ss->x + (ss->length - 1) * xincr[ss->dir];
    yend = ss->y + (ss->length - 1) * yincr[ss->dir];
    if (!ONBOARD(xend, yend)) {
                if (vis) {
                switch(rnd(3)) {
                        case 0:
                                        error("Ship is hanging from the edge of the world");
                                        break;
                        case 1:
                                        error("Try fitting it on the board");
                                        break;
                        case 2:
                                        error("Figure I won't find it if you put it there?");
                                        break;
                        }
            }
                return(0);
    }

    for(l = 0; l < ss->length; ++l) {
                if(collidecheck(b, ss->y+l*yincr[ss->dir], ss->x+l*xincr[ss->dir])) {
                if (vis) {
                                switch(rnd(3)) {
                                case 0:
                                                error("There's already a ship there");
                                                break;
                                case 1:
                                                error("Collision alert!  Aaaaaagh!");
                                                break;
                                case 2:
                                                error("Er, Admiral, what about the other ship?");
                                                break;
                                }
                                }
                return(FALSE);
            }
        }
    return(TRUE);
}

static int
awinna(void)
{
    int i, j;
    ship_t *ss;

    for(i=0; i<2; ++i)
    {
        ss = (i) ? cpuship : plyship;
        for(j=0; j < SHIPTYPES; ++j, ++ss)
            if(ss->length > ss->hits)
                break;
        if (j == SHIPTYPES)
            return(OTHER);
    }
    return(-1);
}

/* a hit on the targeted ship */
static ship_t *
hitship(int x, int y)
{
    ship_t *sb, *ss;
    char sym;
    int oldx, oldy;

    getyx(stdscr, oldy, oldx);
    sb = (turn) ? plyship : cpuship;
    if(!(sym = board[OTHER][x][y]))
        return(NULL);
    for(ss = sb; ss < sb + SHIPTYPES; ++ss)
        if(ss->symbol == sym)
        {
            if (++ss->hits < ss->length) {      /* still afloat? */
                        return(NULL);
            } else { /* sunk */
                int i, j;

                if (!closepack) {
                    for (j = -1; j <= 1; j++) {
                                int bx = ss->x + j * xincr[(ss->dir + 2) % 8];
                                int by = ss->y + j * yincr[(ss->dir + 2) % 8];

                                for (i = -1; i <= ss->length; ++i) {
                                int cx, cy;

                                cx = bx + i * xincr[ss->dir];
                                cy = by + i * yincr[ss->dir];
                                if (ONBOARD(cx, cy)) {
                                                hits[turn][cx][cy] = MARK_MISS;
                                                if (turn % 2 == PLAYER) {
                                                cgoto(cy, cx);
#ifdef A_COLOR
                                                if (has_colors())
                                                                attron(COLOR_PAIR(COLOR_GREEN));
#endif /* A_COLOR */

                                                addch(MARK_MISS);
#ifdef A_COLOR
                                                attrset(0);
#endif /* A_COLOR */
                                                }
                                }
                                }
                }
                }

                for (i = 0; i < ss->length; ++i)
                {
                    int dx = ss->x + i * xincr[ss->dir];
                    int dy = ss->y + i * yincr[ss->dir];

                    hits[turn][dx][dy] = ss->symbol;
                    if (turn % 2 == PLAYER)
                    {
                        cgoto(dy, dx);
                        addch(ss->symbol);
                    }
                }

                move(oldy, oldx);
                return(ss);
            }
        }
    move(oldy, oldx);
    return(NULL);
}

static int
plyturn(void)
{
    ship_t *ss;
    bool hit;
    char const *m;

    m = NULL;
    prompt(1, "Where do you want to shoot? ");
    for (;;)
    {
        getcoord(COMPUTER);
        if (hits[PLAYER][curx][cury])
        {
            prompt(1, "You shelled this spot already! Try again.");
            beep();
        }
        else
            break;
    }
    hit = IS_SHIP(board[COMPUTER][curx][cury]);
    hits[PLAYER][curx][cury] = hit ? MARK_HIT : MARK_MISS;
    cgoto(cury, curx);
#ifdef A_COLOR
    if (has_colors()) {
        if (hit)
            attron(COLOR_PAIR(COLOR_RED));
        else
            attron(COLOR_PAIR(COLOR_GREEN));
    }
#endif /* A_COLOR */
    addch((chtype)hits[PLAYER][curx][cury]);
#ifdef A_COLOR
    attrset(0);
#endif /* A_COLOR */

    prompt(1, "You %s.", hit ? "scored a hit" : "missed");
    if(hit && (ss = hitship(curx, cury)))
    {
        switch(rnd(5))
        {
        case 0:
            m = " You sank my %s!";
            break;
        case 1:
            m = " I have this sinking feeling about my %s....";
            break;
        case 2:
            m = " My %s has gone to Davy Jones's locker!";
            break;
        case 3:
            m = " Glub, glub -- my %s is headed for the bottom!";
            break;
        case 4:
            m = " You'll pick up survivors from my %s, I hope...!";
            break;
        }
        printw(m, ss->name);
        beep();
        return(awinna() == -1);
    }
    return(hit);
}

static int
sgetc(const char *s)
{
    const char *s1;
    int ch;

    refresh();
    for(;;) {
                ch = getch();
                if (islower(ch))
                ch = toupper(ch);

                if (ch == CTRLC)
                uninitgame();

                for (s1=s; *s1 && ch != *s1; ++s1)
                continue;

                if (*s1) {
                addch((chtype)ch);
                refresh();
                return(ch);
                }
        }
}

/* random-fire routine -- implements simple diagonal-striping strategy */
static void
randomfire(int *px, int *py)
{
    static int turncount = 0;
    static int srchstep = BEGINSTEP;
    static int huntoffs;                /* Offset on search strategy */
    int ypossible[BWIDTH * BDEPTH], xpossible[BWIDTH * BDEPTH], nposs;
    int ypreferred[BWIDTH * BDEPTH], xpreferred[BWIDTH * BDEPTH], npref;
    int x, y, i;

    if (turncount++ == 0)
        huntoffs = rnd(srchstep);

    /* first, list all possible moves */
    nposs = npref = 0;
    for (x = 0; x < BWIDTH; x++)
        for (y = 0; y < BDEPTH; y++)
            if (!hits[COMPUTER][x][y])
            {
                xpossible[nposs] = x;
                ypossible[nposs] = y;
                nposs++;
                if (((x+huntoffs) % srchstep) != (y % srchstep))
                {
                    xpreferred[npref] = x;
                    ypreferred[npref] = y;
                    npref++;
                }
            }

    if (npref)
    {
        i = rnd(npref);

        *px = xpreferred[i];
        *py = ypreferred[i];
    }
    else if (nposs)
    {
        i = rnd(nposs);

        *px = xpossible[i];
        *py = ypossible[i];

        if (srchstep > 1)
            --srchstep;
    }
    else
    {
        error("No moves possible?? Help!");
        exit(1);
        /*NOTREACHED*/
    }
}

#define S_MISS  0
#define S_HIT   1
#define S_SUNK  -1

/* fire away at given location */
static bool
cpufire(int x, int y)
{
    bool hit, sunk;
    ship_t *ss;

    ss = NULL;
    hits[COMPUTER][x][y] = (hit = (board[PLAYER][x][y])) ? MARK_HIT : MARK_MISS;
    mvprintw(PROMPTLINE, 0,
        "I shoot at %c%d. I %s!", y + 'A', x, hit ? "hit" : "miss");
    ss = hitship(x, y);
    sunk = hit && ss;
    if (sunk)
        printw(" I've sunk your %s", ss->name);
    clrtoeol();

    pgoto(y, x);
#ifdef A_COLOR
    if (has_colors()) {
        if (hit)
            attron(COLOR_PAIR(COLOR_RED));
        else
            attron(COLOR_PAIR(COLOR_GREEN));
    }
#endif /* A_COLOR */
    addch((chtype)(hit ? SHOWHIT : SHOWSPLASH));
#ifdef A_COLOR
    attrset(0);
#endif /* A_COLOR */

    return(hit ? (sunk ? S_SUNK : S_HIT) : S_MISS);
}

/*
 * This code implements a fairly irregular FSM, so please forgive the rampant
 * unstructuredness below. The five labels are states which need to be held
 * between computer turns.
 */
static bool
cputurn(void)
{
#define POSSIBLE(x, y)  (ONBOARD(x, y) && !hits[COMPUTER][x][y])
#define RANDOM_FIRE     0
#define RANDOM_HIT      1
#define HUNT_DIRECT     2
#define FIRST_PASS      3
#define REVERSE_JUMP    4
#define SECOND_PASS     5
    static int next = RANDOM_FIRE;
    static bool used[4];
    static ship_t ts;
    int navail, x, y, d, n, hit = S_MISS;

    switch(next)
    {
    case RANDOM_FIRE:   /* last shot was random and missed */
    refire:
        randomfire(&x, &y);
        if (!(hit = cpufire(x, y)))
            next = RANDOM_FIRE;
        else
        {
            ts.x = x; ts.y = y;
            ts.hits = 1;
            next = (hit == S_SUNK) ? RANDOM_FIRE : RANDOM_HIT;
        }
        break;

    case RANDOM_HIT:    /* last shot was random and hit */
        used[E/2] = used[S/2] = used[W/2] = used[N/2] = FALSE;
        /* FALLTHROUGH */

    case HUNT_DIRECT:   /* last shot hit, we're looking for ship's long axis */
        for (d = navail = 0; d < 4; d++)
        {
            x = ts.x + xincr[d*2]; y = ts.y + yincr[d*2];
            if (!used[d] && POSSIBLE(x, y))
                navail++;
            else
                used[d] = TRUE;
        }
        if (navail == 0)        /* no valid places for shots adjacent... */
            goto refire;        /* ...so we must random-fire */
        else
        {
            for (d = 0, n = rnd(navail) + 1; n; n--)
                while (used[d])
                    d++;

            assert(d <= 4);

            used[d] = FALSE;
            x = ts.x + xincr[d*2];
            y = ts.y + yincr[d*2];

            assert(POSSIBLE(x, y));

            if (!(hit = cpufire(x, y)))
                next = HUNT_DIRECT;
            else
            {
                ts.x = x; ts.y = y; ts.dir = d*2; ts.hits++;
                next = (hit == S_SUNK) ? RANDOM_FIRE : FIRST_PASS;
            }
        }
        break;

    case FIRST_PASS:    /* we have a start and a direction now */
        x = ts.x + xincr[ts.dir];
        y = ts.y + yincr[ts.dir];
        if (POSSIBLE(x, y) && (hit = cpufire(x, y)))
        {
            ts.x = x; ts.y = y; ts.hits++;
            next = (hit == S_SUNK) ? RANDOM_FIRE : FIRST_PASS;
        }
        else
            next = REVERSE_JUMP;
        break;

    case REVERSE_JUMP:  /* nail down the ship's other end */
        d = ts.dir + 4;
        x = ts.x + ts.hits * xincr[d];
        y = ts.y + ts.hits * yincr[d];
        if (POSSIBLE(x, y) && (hit = cpufire(x, y)))
        {
            ts.x = x; ts.y = y; ts.dir = d; ts.hits++;
            next = (hit == S_SUNK) ? RANDOM_FIRE : SECOND_PASS;
        }
        else
            next = RANDOM_FIRE;
        break;

    case SECOND_PASS:   /* kill squares not caught on first pass */
        x = ts.x + xincr[ts.dir];
        y = ts.y + yincr[ts.dir];
        if (POSSIBLE(x, y) && (hit = cpufire(x, y)))
        {
            ts.x = x; ts.y = y; ts.hits++;
            next = (hit == S_SUNK) ? RANDOM_FIRE: SECOND_PASS;
            break;
        }
        else
            next = RANDOM_FIRE;
        break;
    }

    /* check for continuation and/or winner */
    if (salvo)
    {
        refresh();
        sleep(1);
    }
    if (awinna() != -1)
        return(FALSE);

#ifdef DEBUG
    mvprintw(PROMPTLINE + 2, 0,
                    "New state %d, x=%d, y=%d, d=%d",
                    next, x, y, d);
#endif /* DEBUG */
    return(hit);
}

int
playagain(void)
{
    int j;
    ship_t *ss;

    for (ss = cpuship; ss < cpuship + SHIPTYPES; ss++) {
                for(j = 0; j < ss->length; j++) {
                cgoto(ss->y + j * yincr[ss->dir], ss->x + j * xincr[ss->dir]);
                addch((chtype)ss->symbol);
                }
        }

    if(awinna()) {
                ++cpuwon;
    } else {
                ++plywon;
        }

    j = 18 + strlen(name);
    if(plywon >= 10) {
                ++j;
    } else if(cpuwon >= 10) {
                ++j;
        }

        mvprintw(1,(COLWIDTH-j)/2,
                    "%s: %d     Computer: %d",name,plywon,cpuwon);

    prompt(2, (awinna()) ? "Want to be humiliated again, %s [yn]? "
           : "Going to give me a chance for revenge, %s [yn]? ",name);
    return(sgetc("YN") == 'Y');
}

static void
usage(void)
{
                fprintf(stderr, "Usage: battle [-s | -b] [-c]\n");
                fprintf(stderr, "\tWhere the options are:\n");
                fprintf(stderr, "\t-s : salvo     - One shot per ship in play\n");
                fprintf(stderr, "\t-b : blitz     - Fire until you miss\n");
                fprintf(stderr, "\t-c : closepack - Ships may be adjacent\n");
                fprintf(stderr, "Blitz and Salvo are mutually exclusive\n");
                exit(1);
}

static int
scount(int who)
{
    int i, shots;
    ship_t *sp;

    if (who)
        sp = cpuship;   /* count cpu shots */
    else
        sp = plyship;   /* count player shots */

    for (i=0, shots = 0; i < SHIPTYPES; i++, sp++)
    {
        if (sp->hits >= sp->length)
            continue;           /* dead ship */
        else
            shots++;
    }
    return(shots);
}

int
main(int argc, char **argv)
{
        int ch;

        /* revoke */
        setgid(getgid());

        while ((ch = getopt(argc, argv, "bsc")) != -1) {
                switch (ch) {
                        case 'b':
                                blitz = 1;
                                break;
                        case 's':
                                salvo = 1;
                                break;
                        case 'c':
                                closepack = 1;
                                break;
                        case '?':
                        default:
                                usage();
                }
        }
        argc -= optind;
        argv += optind;

        if (blitz && salvo)
                usage();

    intro();

        do {
                initgame();
                while(awinna() == -1) {
                        if (blitz) {
                                while(turn ? cputurn() : plyturn())
                                        continue;
                        } else if (salvo) {
                                int i;

                                i = scount(turn);
                                while (i--) {
                                        if (turn) {
                                                if (cputurn() && awinna() != -1)
                                                i = 0;
                                        } else {
                                                if (plyturn() && awinna() != -1)
                                                i = 0;
                                        }
                                }
                        } else {        /* Normal game */
                                if(turn)
                                        cputurn();
                                else
                                        plyturn();
                        }
                        turn = OTHER;
                }
        } while (playagain());

    uninitgame();
    exit(0);
}