LithosAnanake/src/starkernel/repl.c

/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  Licensed under the StarForth License, Version 1.0
*/

/**
 * repl.c - Emergency FORTH REPL for LithosAnanke kernel
 *
 * Direct adaptation of src/repl.c for the freestanding kernel context.
 * Replaces libc stdio (fgets/printf/fflush) with HAL serial I/O:
 *   - Input:  console_getc() non-blocking poll with local echo and backspace
 *   - Output: console_puts() / console_putc()
 *
 * Idle spin:  polls console_getc() and services the adaptive heartbeat.
 *             The timer ISR's top half (heartbeat_tick()) latches one
 *             sample per interrupt; the idle spin drains it every
 *             iteration via heartbeat_service() (item 0.8, FABRIC.md §26)
 *             and calls sk_repl_idle() once per SK_IDLE_BEAT_INTERVAL ticks
 *             for coarser subsystem dispatch. On QEMU TCG the ISR must fire
 *             for ticks to advance — check "Heartbeat: N ticks" in the
 *             serial log to confirm.
 *
 * Runs with interrupts enabled so the APIC heartbeat fires normally.
 * Designed as the last thing kernel_main does before the idle loop.
 */

#include "starkernel/repl.h"
#include "console.h"
#include "vm.h"
#include "version.h"
#include "starkernel/timer.h"
#include "starkernel/arch.h"
#include "word_source/include/keyboard_words.h"
#include <stdint.h>
#include <string.h>

/* FABRIC.md 4.4: "ok>" (including its trailing space) renders in bright
 * cyan, 0x55FFFF -- reuses FB_ANSI_PALETTE[14]. Sent as a real SGR escape
 * so it colors both the framebuffer (parsed by vt100.c's apply_sgr()) and
 * any ANSI-aware serial terminal, per 4.4c's "identical on both" goal. */
#define SK_PROMPT_TEXT "\x1b[38;2;85;255;255mok> \x1b[39m"

const char lithos_version[64] = LITHOS_VERSION_STR;


/*===========================================================================
 * USE-word dispatch: which VM receives REPL input.
 *
 * NULL means "use the REPL's own vm parameter" (default — Mama).
 * Set via sk_repl_set_active_vm(); read by sk_repl_run() each iteration.
 *===========================================================================*/

static VM *g_repl_active_vm = (void *)0;

void sk_repl_set_active_vm(VM *vm) { g_repl_active_vm = vm; }
VM  *sk_repl_get_active_vm(void)   { return g_repl_active_vm; }

/*===========================================================================
 * Idle heartbeat service
 *
 * Called from sk_readline when heartbeat_ticks() has advanced by at least
 * SK_IDLE_BEAT_INTERVAL since the last service call.  Extend this function
 * as higher-level subsystems (msg_fabric, capsule scheduler) come online.
 *
 * TODO: cadence policy and subsystem dispatch belong in Compudynamics once
 * that layer governs cooperative VM execution.
 *===========================================================================*/

#define SK_IDLE_BEAT_INTERVAL  100u   /* ticks between idle service calls (1 s at 100 Hz) */

static uint64_t g_last_beat_tick;    /* zero-initialized (BSS) */

static void sk_repl_idle(void)
{
    /* Placeholder — extended by higher-level subsystems as they come online */
    (void)0;
}

/*===========================================================================
 * FABRIC.md item 4.4v: keyboard-to-REPL bridge.
 *
 * Translates sk_key_event_poll()'s converged Linux-keycode-namespace
 * stream (keyboard_words.c -- one implementation shared with KEY-EVENT,
 * live-verified on all three architectures per item 4.3.5f) into the same
 * byte stream sk_readline() already reads from console_getc(): -1 for
 * "nothing ready", else a raw ASCII byte with '\n'/0x7F meaning the same
 * thing they mean for the serial path below.
 *
 * Table covers exactly the keys a line editor needs -- letters, digits,
 * the standard US-QWERTY punctuation row, space, enter, backspace, tab
 * (for the Ctrl+TAB toggle interception, 4.4y/4.4u step 8) -- not full
 * keyboard coverage. Keycodes are Linux input-event-codes.h values,
 * confirmed against this build host's own header, not guessed (§25.0
 * rule 4). Index 0 means "no mapping"; arrows/F-keys/etc. fall through
 * unmapped and are silently dropped, consistent with this REPL's
 * append/backspace-only editing model (4.4u: no mid-line cursor
 * movement).
 *===========================================================================*/

#define SK_KBD_TABLE_SIZE 98u   /* highest keycode used below is KEY_RIGHTCTRL=97 */

static const char sk_kbd_unshifted[SK_KBD_TABLE_SIZE] = {
    [2]='1',[3]='2',[4]='3',[5]='4',[6]='5',[7]='6',[8]='7',[9]='8',[10]='9',[11]='0',
    [12]='-',[13]='=',
    [16]='q',[17]='w',[18]='e',[19]='r',[20]='t',[21]='y',[22]='u',[23]='i',[24]='o',[25]='p',
    [26]='[',[27]=']',
    [30]='a',[31]='s',[32]='d',[33]='f',[34]='g',[35]='h',[36]='j',[37]='k',[38]='l',
    [39]=';',[40]='\'',[41]='`',[43]='\\',
    [44]='z',[45]='x',[46]='c',[47]='v',[48]='b',[49]='n',[50]='m',
    [51]=',',[52]='.',[53]='/',
    [57]=' ',
};

static const char sk_kbd_shifted[SK_KBD_TABLE_SIZE] = {
    [2]='!',[3]='@',[4]='#',[5]='$',[6]='%',[7]='^',[8]='&',[9]='*',[10]='(',[11]=')',
    [12]='_',[13]='+',
    [16]='Q',[17]='W',[18]='E',[19]='R',[20]='T',[21]='Y',[22]='U',[23]='I',[24]='O',[25]='P',
    [26]='{',[27]='}',
    [30]='A',[31]='S',[32]='D',[33]='F',[34]='G',[35]='H',[36]='J',[37]='K',[38]='L',
    [39]=':',[40]='"',[41]='~',[43]='|',
    [44]='Z',[45]='X',[46]='C',[47]='V',[48]='B',[49]='N',[50]='M',
    [51]='<',[52]='>',[53]='?',
    [57]=' ',
};

#define SK_KEY_BACKSPACE  14u
#define SK_KEY_TAB        15u
#define SK_KEY_ENTER      28u
#define SK_KEY_LEFTSHIFT  42u
#define SK_KEY_RIGHTSHIFT 54u
#define SK_KEY_LEFTALT    56u
#define SK_KEY_RIGHTALT   100u

static int g_kbd_shift_down;   /* zero-initialized (BSS) */
static int g_kbd_alt_down;

/* Drains and translates one physically-typed key. Modifier state persists
 * across calls (a real keyboard's shift/alt state is global, not
 * per-line). Alt+TAB is intercepted here and drives the graphics/text
 * toggle directly (console_fb_toggle_graphics(), the same state-machine
 * transition the ALT+TAB FORTH word calls) -- never reaches the line
 * buffer as a character either way. */
static int sk_kbd_getc(void)
{
    uint16_t keycode;
    int pressed;

    while (sk_key_event_poll(&keycode, &pressed)) {
        if (keycode == SK_KEY_LEFTSHIFT || keycode == SK_KEY_RIGHTSHIFT) {
            g_kbd_shift_down = pressed;
            continue;
        }
        if (keycode == SK_KEY_LEFTALT || keycode == SK_KEY_RIGHTALT) {
            g_kbd_alt_down = pressed;
            continue;
        }
        if (!pressed) continue;   /* only act on press/repeat */

        if (keycode == SK_KEY_TAB) {
            if (g_kbd_alt_down) console_fb_toggle_graphics();
            continue;   /* bare TAB: not mapped, same as arrows/F-keys */
        }
        if (keycode == SK_KEY_ENTER) return '\n';
        if (keycode == SK_KEY_BACKSPACE) return 0x7F;

        if (keycode < SK_KBD_TABLE_SIZE) {
            char c = g_kbd_shift_down ? sk_kbd_shifted[keycode] : sk_kbd_unshifted[keycode];
            if (c) return (unsigned char)c;
        }
        /* unmapped keycode -- drop and keep draining */
    }
    return -1;
}

/*===========================================================================
 * sk_readline - line read from serial console with echo
 *
 * Non-blocking poll of console_getc().  While no character is ready the idle
 * spin services the adaptive heartbeat at SK_IDLE_BEAT_INTERVAL tick cadence.
 * Supports backspace (0x7F and \b) and ignores other control characters.
 * Returns the number of characters placed in buf (not counting '\0').
 *===========================================================================*/

static int sk_readline(char *buf, int size)
{
    int n = 0;

    buf[0] = '\0';
    console_fb_draw_cursor();   /* show the cursor at the bare prompt, before any input */

    for (;;) {
        int c = console_getc();   /* non-blocking poll */
        if (c < 0) c = sk_kbd_getc();   /* FABRIC.md 4.4v: second source, same buffer */

        if (c < 0) {
            /* Service the heartbeat bottom half every idle iteration, not
             * gated by SK_IDLE_BEAT_INTERVAL (item 0.8, FABRIC.md §26):
             * heartbeat_service() drains at most one latched sample per
             * call, so a coarse gate here would silently lose or merge
             * samples between ISR-latched ticks. sk_repl_idle() below is
             * a separate, deliberately coarser cadence for higher-level
             * subsystem dispatch, unrelated to sample fidelity. */
            heartbeat_service();

            uint64_t now = heartbeat_ticks();
            if (now - g_last_beat_tick >= SK_IDLE_BEAT_INTERVAL) {
                g_last_beat_tick = now;
                sk_repl_idle();
            }
            /*
             * Do NOT use hlt here: QEMU single-threaded TCG can't process
             * its APIC timer callbacks while the guest CPU is halted (the
             * event loop and the TCG thread share the same OS thread).
             * Interrupts are delivered at TB boundaries in a tight loop.
             * On real hardware a wfi/hlt would be appropriate; add it here
             * under an #ifdef REAL_HARDWARE guard when that path is needed.
             */
            arch_relax();   /* PAUSE — reduce power, maintain tight poll */
            continue;
        }

        if (c == '\r' || c == '\n') {
            console_fb_erase_cursor();   /* leaving this cell without drawing a char over it */
            console_putc('\n');
            break;
        }

        /* backspace: DEL (0x7F) or BS (0x08) */
        if ((c == 0x7F || c == '\b') && n > 0) {
            n--;
            buf[n] = '\0';
            /* VT100 erase: move back, overwrite with space, move back again */
            console_putc('\b');
            console_putc(' ');
            console_putc('\b');
            console_fb_draw_cursor();
            continue;
        }

        if (c < 0x20) continue;       /* ignore other control characters */
        if (n >= size - 1) continue;  /* buffer full — drop character */

        buf[n++] = (char)c;
        buf[n] = '\0';
        console_putc((char)c);        /* echo */
        console_fb_draw_cursor();
    }

    buf[n] = '\0';
    return n;
}

/*===========================================================================
 * sk_repl - Emergency FORTH REPL
 *
 * Mirrors vm_repl() from src/repl.c:
 *   - Sets vm->emergency_console = 1 for the duration (this IS the emergency
 *     console; bypasses ACL so zuse authentication is not required to recover)
 *   - Prints "zuse)ok> " when zuse_session=1, else "ok> "
 *   - Reads a line via sk_readline (non-blocking, heartbeat-serviced)
 *   - Calls vm_interpret
 *   - Prints " ok" or " ERROR"
 *   - When EMERGENCY_CONSOLE_ENABLED=1: resets vm->error and loops (recovery)
 *   - When EMERGENCY_CONSOLE_ENABLED=0: halts VM on error (no fallthrough surface)
 *===========================================================================*/

#if !EMERGENCY_CONSOLE_ENABLED
static void sk_fault_handler(VM *vm) {
    console_println("VM fault — emergency console disabled; halting");
    vm->halted = 1;
}
#endif

/*===========================================================================
 * sk_repl_step - Execute one REPL turn on a VM and return.
 *
 * Prints the VM's prompt, reads one input line, interprets it, prints
 * ok/ERROR, then returns.  Used by the Compudynamics VM-STEP primitive
 * so Hera can give a single REPL quantum to any child VM without
 * surrendering control for the full sk_repl_run() loop.
 *
 * Returns 1 if the VM is still running, 0 if it halted during this turn.
 *===========================================================================*/

int sk_repl_step(VM *vm)
{
    char input[INPUT_BUFFER_SIZE];   /* FABRIC.md 4.4w: matches the strip's input width */

    if (!vm || vm->halted) return 0;

    {
        /* Unified prompt (FABRIC.md 4.4a): console_putc()'s existing per-line
         * "[VMName] " prefix (console.c, g_active_vm_name) already supplies the
         * bracket -- print only "ok> " here, don't build a second one. The
         * emergency_console bypass is a security decision, not a display one --
         * it still applies only to Hera's bare prompt, per FABRIC.md 4.4. */
        const char *vn = console_get_vm_name();
        int is_hera = (!vn || (vn[0]=='H' && vn[1]=='e' && vn[2]=='r' && vn[3]=='a' && vn[4]=='\0'));
        vm->emergency_console = is_hera ? (vm->zuse_session ? 0 : 1) : 0;
        console_puts(SK_PROMPT_TEXT);
    }

    sk_readline(input, sizeof(input));

    if (input[0] == '\0') {
        console_puts(" ok\n");
        return vm->halted ? 0 : 1;
    }

    vm_interpret(vm, input);

    /* ABORT stops mid-line but leaves the flag set for the caller to
     * consume -- this REPL step is that boundary. Clear it here so the
     * next line isn't silently refused by vm_interpret's own check. */
    vm->abort_requested = 0;

    if (vm->error) {
        console_puts(" ERROR\n");
        vm->error = 0;
    } else {
        console_puts(" ok\n");
    }

    return vm->halted ? 0 : 1;
}

void sk_repl_run(VM *vm)
{
    char input[INPUT_BUFFER_SIZE];   /* FABRIC.md 4.4w: matches the strip's input width */
    VM  *active;

    vm->halted = 0;

    while (!vm->halted) {
        /* USE may redirect input to a different VM each iteration */
        active = g_repl_active_vm ? g_repl_active_vm : vm;

        /* Unified prompt (FABRIC.md 4.4a): console_putc()'s existing per-line
         * "[VMName] " prefix (console.c, g_active_vm_name) already supplies the
         * bracket -- print only "ok> " here, don't build a second one. The
         * emergency_console bypass is a security decision, not a display one --
         * it still applies only to Hera's bare prompt, per FABRIC.md 4.4. */
        {
            const char *vn = console_get_vm_name();
            int is_hera = (!vn || (vn[0]=='H' && vn[1]=='e' && vn[2]=='r' && vn[3]=='a' && vn[4]=='\0'));
            active->emergency_console = is_hera ? (active->zuse_session ? 0 : 1) : 0;
            console_puts(SK_PROMPT_TEXT);
        }

        sk_readline(input, sizeof(input));

        if (input[0] == '\0') {
            console_puts(" ok\n");
            continue;
        }

        vm_interpret(active, input);

        /* ABORT stops mid-line but leaves the flag set for the caller to
         * consume -- this REPL step is that boundary. Clear it here so the
         * next line isn't silently refused by vm_interpret's own check. */
        active->abort_requested = 0;

        if (active->error) {
            console_puts(" ERROR\n");
            active->error = 0;
        } else {
            console_puts(" ok\n");
        }
    }
}

void sk_repl(VM *vm)
{
    /* FABRIC.md item 4.4j: boot and POST (both already returned by the time
     * sk_repl() is called) stay on font_8x16.c/VT100 by design; the
     * interactive REPL -- this function -- is the boundary where TTF-TEXT
     * takes over. One-shot: console_fb_enable_ttf() no-ops on any later
     * call. */
    console_fb_enable_ttf();

    console_println(lithos_version);
    console_puts("StarForth Version ");    console_println(STARFORTH_VERSION);
    console_println("");
    console_println("StarForth Emergency CLI");
    console_println("FORTH-79 interpreter — type BYE or power off to exit");
    console_println("");

    sk_repl_run(vm);
}