/**
 * @file akgl_frontend.c
 * @brief Tests the standalone SDL frontend: the host, not the adaptors.
 *
 * tests/akgl_backends.c stands in for a host and asserts that each adaptor
 * reaches the right libakgl call. This file asserts the thing that was missing
 * until the frontend existed: that there *is* a host, that it composes the two
 * output paths so a program's bytes reach the window and stdout alike, that its
 * event pump feeds the keystroke ring a script reads, that its line editor turns
 * keystrokes into typed lines, and that closing the window ends a program that
 * would otherwise never stop.
 *
 * Everything runs under the dummy video and audio drivers with a software
 * renderer, following deps/libakgl/tests/draw.c, so it needs no display and no
 * sound card. The font is the reference's own Commodore one -- the acceptance
 * criterion in TODO.md section 3 asks for the drawn text to be in that font, and
 * the frontend is the only place that opens it.
 *
 * Only one frontend may exist at a time: libakgl's renderer and window are
 * process globals, and a host that never calls akgl_game_init() populates them
 * itself. Each test therefore brings one up and takes it down again.
 */

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

#include <SDL3/SDL.h>

#include <akerror.h>

#include <akgl/actor.h>
#include <akgl/controller.h>
#include <akgl/error.h>

#include <akbasic/error.h>
#include <akbasic/frontend.h>
#include <akbasic/runtime.h>

#include "testutil.h"

/** @brief Window size. Small enough to read the whole target back cheaply. */
#define WINDOW_W	320
/** @brief Window height. */
#define WINDOW_H	200

/* Both of these carry pools far too large for a stack. */
static akbasic_AkglFrontend FRONTEND;
static akbasic_Runtime RUNTIME;
static char OUTPUT[8192];
static FILE *MIRROR = NULL;
static FILE *PROGRAM = NULL;

/** @brief Report whether any pixel in a rectangle is not the background. */
static bool anything_drawn(SDL_Surface *shot, int x0, int y0, int w, int h)
{
    uint8_t r = 0;
    uint8_t g = 0;
    uint8_t b = 0;
    uint8_t a = 0;
    int x = 0;
    int y = 0;

    if ( shot == NULL ) {
	return false;
    }
    for ( y = y0; y < y0 + h; y++ ) {
	for ( x = x0; x < x0 + w; x++ ) {
	    if ( !SDL_ReadSurfacePixel(shot, x, y, &r, &g, &b, &a) ) {
		continue;
	    }
	    if ( r != 0 || g != 0 || b != 0 ) {
		return true;
	    }
	}
    }
    return false;
}

/**
 * @brief Queue one key-down, exactly as a keyboard would.
 *
 * Straight into SDL's own queue rather than into libakgl's ring, so the
 * frontend's event pump is the thing under test: nothing reaches the
 * interpreter unless pump_events() drained this and handed it over.
 */
static void push_key(int keycode)
{
    SDL_Event event;

    memset(&event, 0, sizeof(event));
    event.type = SDL_EVENT_KEY_DOWN;
    event.key.key = keycode;
    SDL_PushEvent(&event);
}

/** @brief Queue a whole typed line, terminator included. */
static void push_line(const char *text)
{
    size_t i = 0;

    for ( i = 0; text[i] != '\0'; i++ ) {
	push_key((int)(unsigned char)text[i]);
    }
    push_key('\r');
}

/** @brief Queue the event a window manager sends when the close button is hit. */
static void push_quit(void)
{
    SDL_Event event;

    memset(&event, 0, sizeof(event));
    event.type = SDL_EVENT_QUIT;
    SDL_PushEvent(&event);
}

/**
 * @brief Bring up a frontend whose mirror is a buffer this file can read.
 *
 * @param source A program to feed through the stdio half, or NULL to type it.
 */
static akerr_ErrorContext AKERR_NOIGNORE *start_frontend(const char *source)
{
    PREPARE_ERROR(errctx);

    memset(OUTPUT, 0, sizeof(OUTPUT));
    MIRROR = fmemopen(OUTPUT, sizeof(OUTPUT), "w");
    FAIL_ZERO_RETURN(errctx, (MIRROR != NULL), AKERR_IO, "could not open the mirror buffer");
    setvbuf(MIRROR, NULL, _IONBF, 0);

    PROGRAM = NULL;
    if ( source != NULL ) {
	PROGRAM = fmemopen((void *)(uintptr_t)source, strlen(source), "r");
	FAIL_ZERO_RETURN(errctx, (PROGRAM != NULL), AKERR_IO,
			 "could not open the program buffer");
    }

    PASS(errctx, akbasic_frontend_akgl_init(&FRONTEND, "akbasic frontend test",
					    WINDOW_W, WINDOW_H,
					    AKBASIC_TEST_C64_FONT,
					    AKBASIC_FRONTEND_FONT_SIZE,
					    MIRROR, PROGRAM));
    PASS(errctx, akbasic_frontend_akgl_attach(&FRONTEND, &RUNTIME));
    SUCCEED_RETURN(errctx);
}

static void stop_frontend(void)
{
    akbasic_frontend_akgl_shutdown(&FRONTEND);
    if ( MIRROR != NULL ) {
	fclose(MIRROR);
	MIRROR = NULL;
    }
    if ( PROGRAM != NULL ) {
	fclose(PROGRAM);
	PROGRAM = NULL;
    }
}

/**
 * @brief A program run through the frontend reaches stdout *and* the window.
 *
 * This is the assertion the whole frontend exists for, and it is two assertions
 * on purpose: the mirrored bytes are what the golden corpus compares, and the
 * lit pixels are what a user actually sees. Before the frontend existed an AKGL
 * build produced the first and not the second.
 */
static akerr_ErrorContext AKERR_NOIGNORE *test_program_reaches_both(void)
{
    PREPARE_ERROR(errctx);
    SDL_Surface *shot = NULL;

    PASS(errctx, start_frontend("10 PRINT \"HELLO\"\n20 QUIT\n"));
    PASS(errctx, akbasic_runtime_start(&RUNTIME, AKBASIC_MODE_RUNSTREAM));
    PASS(errctx, akbasic_frontend_akgl_drive(&FRONTEND, &RUNTIME));

    /* Byte for byte, exactly what the stdio-only driver would have written. */
    TEST_REQUIRE_STR(OUTPUT, "HELLO\n");
    /* And the same characters are in the grid the window draws from. */
    TEST_REQUIRE_STR(FRONTEND.akglstate.text[0], "HELLO");

    /*
     * Asserted as "the first five cells have something in them and the sixth
     * does not", rather than against particular pixels: which ones a glyph
     * lights is FreeType's business. What is being proved is that five
     * characters of Commodore font reached the renderer where the sink's cursor
     * said they would.
     */
    shot = SDL_RenderReadPixels(FRONTEND.renderer->sdl_renderer, NULL);
    TEST_REQUIRE(shot != NULL, "could not read the render target back");
    TEST_REQUIRE(anything_drawn(shot, 0, 0,
				5 * FRONTEND.akglstate.cellw,
				FRONTEND.akglstate.cellh),
		 "HELLO should have been drawn into the first five character cells");
    TEST_REQUIRE(!anything_drawn(shot, 0,
				 3 * FRONTEND.akglstate.cellh,
				 WINDOW_W, FRONTEND.akglstate.cellh),
		 "nothing was printed on the fourth row, so nothing should be drawn there");
    SDL_DestroySurface(shot);

    stop_frontend();
    SUCCEED_RETURN(errctx);
}

/**
 * @brief The event pump is what carries a keystroke to the interpreter.
 *
 * Pushed into SDL's queue and read back through the frontend's own input
 * backend, so every link in the chain the host owns is in the path: SDL queue,
 * pump_events, akgl_controller_handle_event, the ring, the backend.
 */
static akerr_ErrorContext AKERR_NOIGNORE *test_pump_feeds_input(void)
{
    PREPARE_ERROR(errctx);
    bool running = false;
    bool available = false;
    int keycode = 0;

    PASS(errctx, start_frontend("10 QUIT\n"));
    PASS(errctx, FRONTEND.input.flush_keys(&FRONTEND.input));

    /* Nothing pumped yet: the ring is empty and that is success, not an error. */
    PASS(errctx, FRONTEND.input.poll_key(&FRONTEND.input, &keycode, &available));
    TEST_REQUIRE(!available, "an unpumped frontend should have no keys waiting");

    push_key(SDLK_A);
    PASS(errctx, akbasic_frontend_akgl_pump(&FRONTEND, &running));
    TEST_REQUIRE(running, "a key event should not stop the frontend");

    PASS(errctx, FRONTEND.input.poll_key(&FRONTEND.input, &keycode, &available));
    TEST_REQUIRE(available, "the pump should have handed the key to the interpreter");
    TEST_REQUIRE_INT(keycode, SDLK_A);

    stop_frontend();
    SUCCEED_RETURN(errctx);
}

/**
 * @brief Closing the window stops a program that would otherwise never stop.
 *
 * `10 GOTO 10` is the case that matters: an unbounded run() would own the
 * process forever and the close button would do nothing. The bounded frame loop
 * is what makes this test finish at all.
 */
static akerr_ErrorContext AKERR_NOIGNORE *test_window_close_stops(void)
{
    PREPARE_ERROR(errctx);
    bool running = true;

    PASS(errctx, start_frontend("10 GOTO 10\n"));
    PASS(errctx, akbasic_runtime_load(&RUNTIME, "10 GOTO 10\n"));
    PASS(errctx, akbasic_runtime_start(&RUNTIME, AKBASIC_MODE_RUN));

    push_quit();
    PASS(errctx, akbasic_frontend_akgl_drive(&FRONTEND, &RUNTIME));
    TEST_REQUIRE(!FRONTEND.running, "the close event should have stopped the frontend");
    TEST_REQUIRE(RUNTIME.mode != AKBASIC_MODE_QUIT,
		 "closing the window stops the host, it does not QUIT the script");

    /* And a pump after the close keeps reporting the same thing. */
    PASS(errctx, akbasic_frontend_akgl_pump(&FRONTEND, &running));
    TEST_REQUIRE(!running, "a closed frontend stays closed");

    stop_frontend();
    SUCCEED_RETURN(errctx);
}

/**
 * @brief The line editor turns keystrokes into a line, echoed as it is typed.
 *
 * Read through the sink directly rather than through the REPL, because what is
 * being asserted here is the editing itself: the fold to upper case that the
 * ring's missing modifier state forces, the backspace, and the echo landing in
 * the grid where the cursor says it is.
 */
static akerr_ErrorContext AKERR_NOIGNORE *test_line_editor(void)
{
    PREPARE_ERROR(errctx);
    char line[64];
    bool eof = true;

    PASS(errctx, start_frontend(NULL));
    PASS(errctx, FRONTEND.input.flush_keys(&FRONTEND.input));

    /* "prXnt" with the X backspaced away, typed in lower case. */
    push_key('p');
    push_key('r');
    push_key('x');
    push_key('\b');
    push_key('i');
    push_key('n');
    push_key('t');
    push_key('\r');

    PASS(errctx, FRONTEND.akglsink.readline(&FRONTEND.akglsink, line, sizeof(line), &eof));
    TEST_REQUIRE(!eof, "a submitted line is not end of input");
    /*
     * Upper case because akgl_controller_poll_key() reports a keycode and no
     * modifier state, so Shift is invisible and lower case is unreachable. A
     * C128 is upper case too, which is why this is the right resolution rather
     * than merely the available one. Filed upstream.
     */
    TEST_REQUIRE_STR(line, "PRINT");
    /* The echo is in the grid, and the backspace really removed a character. */
    TEST_REQUIRE_STR(FRONTEND.akglstate.text[0], "PRINT");
    TEST_REQUIRE_INT(FRONTEND.akglstate.cursorrow, 1);
    TEST_REQUIRE_INT(FRONTEND.akglstate.cursorcol, 0);
    TEST_REQUIRE(!FRONTEND.akglstate.editing, "the editor should be idle once the line is in");

    /* Escape abandons a line rather than submitting it. */
    push_key('z');
    push_key(0x1b);
    push_key('o');
    push_key('k');
    push_key('\r');
    PASS(errctx, FRONTEND.akglsink.readline(&FRONTEND.akglsink, line, sizeof(line), &eof));
    TEST_REQUIRE_STR(line, "OK");
    TEST_REQUIRE_STR(FRONTEND.akglstate.text[1], "OK");

    /* A closed window ends the wait, reported as end of input rather than raised. */
    push_quit();
    PASS(errctx, FRONTEND.akglsink.readline(&FRONTEND.akglsink, line, sizeof(line), &eof));
    TEST_REQUIRE(eof, "closing the window during an INPUT is end of input");

    stop_frontend();
    SUCCEED_RETURN(errctx);
}

/**
 * @brief A whole REPL session typed at the window, ending with QUIT.
 *
 * The end-to-end case: keystrokes into SDL's queue, out through the editor, into
 * the interpreter, and the result on both output paths. Nothing here is mocked
 * except the keyboard and the mirror.
 */
static akerr_ErrorContext AKERR_NOIGNORE *test_repl_session(void)
{
    PREPARE_ERROR(errctx);

    PASS(errctx, start_frontend(NULL));
    PASS(errctx, FRONTEND.input.flush_keys(&FRONTEND.input));

    /*
     * Every keystroke queued up front, and the session ended with a typed QUIT
     * rather than a close event: the pump drains the whole SDL queue in one
     * call, so a close event queued here would be seen before the first
     * keystroke was ever read.
     */
    push_line("10 print 1");
    push_line("run");
    push_line("quit");

    PASS(errctx, akbasic_runtime_start(&RUNTIME, AKBASIC_MODE_REPL));
    PASS(errctx, akbasic_frontend_akgl_drive(&FRONTEND, &RUNTIME));

    TEST_REQUIRE_INT(RUNTIME.mode, AKBASIC_MODE_QUIT);
    /* The reference prints READY at the prompt and after a RUN. */
    TEST_REQUIRE_STR(OUTPUT, "READY\n1\nREADY\n");

    stop_frontend();
    SUCCEED_RETURN(errctx);
}

/** @brief Every entry point validates its pointers before touching SDL. */
static akerr_ErrorContext AKERR_NOIGNORE *test_arguments_refused(void)
{
    PREPARE_ERROR(errctx);
    bool running = false;

    TEST_REQUIRE_STATUS(akbasic_frontend_akgl_init(NULL, "t", WINDOW_W, WINDOW_H,
						   AKBASIC_TEST_C64_FONT, 16, NULL, NULL),
			AKERR_NULLPOINTER);
    TEST_REQUIRE_STATUS(akbasic_frontend_akgl_init(&FRONTEND, "t", WINDOW_W, WINDOW_H,
						   NULL, 16, NULL, NULL),
			AKERR_NULLPOINTER);
    /* A zero-point font would divide by zero measuring the character grid. */
    TEST_REQUIRE_STATUS(akbasic_frontend_akgl_init(&FRONTEND, "t", WINDOW_W, WINDOW_H,
						   AKBASIC_TEST_C64_FONT, 0, NULL, NULL),
			AKBASIC_ERR_VALUE);
    TEST_REQUIRE_STATUS(akbasic_frontend_akgl_attach(NULL, &RUNTIME), AKERR_NULLPOINTER);
    TEST_REQUIRE_STATUS(akbasic_frontend_akgl_pump(NULL, &running), AKERR_NULLPOINTER);
    TEST_REQUIRE_STATUS(akbasic_frontend_akgl_drive(&FRONTEND, NULL), AKERR_NULLPOINTER);
    /* Shutting down something that was never brought up is not an error. */
    akbasic_frontend_akgl_shutdown(NULL);
    SUCCEED_RETURN(errctx);
}

int main(void)
{
    PREPARE_ERROR(errctx);

    SDL_SetHint(SDL_HINT_VIDEO_DRIVER, "dummy");
    SDL_SetHint(SDL_HINT_AUDIO_DRIVER, "dummy");
    SDL_SetHint(SDL_HINT_RENDER_DRIVER, "software");

    ATTEMPT {
	CATCH(errctx, akgl_error_init());
	CATCH(errctx, akbasic_error_register());

	CATCH(errctx, test_arguments_refused());
	CATCH(errctx, test_program_reaches_both());
	CATCH(errctx, test_pump_feeds_input());
	CATCH(errctx, test_window_close_stops());
	CATCH(errctx, test_line_editor());
	CATCH(errctx, test_repl_session());
    } CLEANUP {
	stop_frontend();
    } PROCESS(errctx) {
    } HANDLE_DEFAULT(errctx) {
	LOG_ERROR_WITH_MESSAGE(errctx, "akgl frontend test failed");
	akbasic_test_failures += 1;
	/*
	 * FINISH_NORETURN rather than FINISH, matching tests/akgl_backends.c:
	 * FINISH expands a `return __err_context` that this int-returning
	 * function cannot compile even where the branch is unreachable.
	 * HANDLE_DEFAULT has already marked the context handled, so nothing
	 * aborts.
	 */
    } FINISH_NORETURN(errctx);

    return akbasic_test_failures;
}