#define _POSIX_C_SOURCE 200809L
/* colitur-x -- a raw Xlib front-end for colitur.
 *
 * Reads `colitur emit --format csv` on stdin, draws the year as a month
 * grid coloured by the day's liturgical colour, and shows the selected
 * day's readings underneath. Arrow keys / hjkl move, n and p change month,
 * q quits.
 *
 * Links libX11 and libXft. No toolkit, no runtime config: edit config.h.
 * SPDX-License-Identifier: GPL-3.0-or-later
 */
#include <X11/Xlib.h>
#include <X11/Xft/Xft.h>
#include <X11/keysym.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "config.h"

#define MAXDAYS 400
#define F 16                    /* CSV columns, see colitur emit --format csv */

typedef struct { char *f[F]; } Row;

static Row rows[MAXDAYS];
static int nrows;
static int cur;                 /* selected row */

static Display *dpy;
static Window win;
static Pixmap buf;              /* draw off-screen, then blit */
static GC gc;
static int bufw, bufh;
static int scr;
static XftFont *fnt, *fnt_big;
static XftDraw *xd;
static Visual *vis;
static Colormap cmap;

/* --- tiny CSV reader: no quoting in colitur's output except commas in
   citations, which are quoted. Handle both. ------------------------------ */
static int split(char *line, char **out)
{
	int n = 0; char *p = line;
	while (n < F) {
		if (*p == '"') {
			out[n++] = ++p;
			while (*p && *p != '"') p++;
			if (*p) *p++ = 0;
			if (*p == ',') p++;
		} else {
			out[n++] = p;
			while (*p && *p != ',') p++;
			if (*p) *p++ = 0; else break;
		}
	}
	return n;
}

/* The header line is DETECTED, not assumed. Skipping the first line
   unconditionally punishes the obvious way to look at one month --
   `... | grep "^2027-04" | colitur-x` -- by silently eating the 1st,
   which is a filter this program should compose with rather than fight.
   A header is exactly the line beginning "date,"; anything else is a day. */
static int is_header(const char *line)
{
	return strncmp(line, "date,", 5) == 0;
}

static void load(void)
{
	char buf[4096];
	int first = 1;
	while (nrows < MAXDAYS && fgets(buf, sizeof buf, stdin)) {
		buf[strcspn(buf, "\n")] = 0;
		if (first && is_header(buf)) { first = 0; continue; }
		first = 0;
		if (buf[0] == 0) continue;
		char *dup = strdup(buf);
		if (!dup) break;
		if (split(dup, rows[nrows].f) >= 12) nrows++; else free(dup);
	}
}

/* Start on TODAY if the input covers it. Reading the clock is a
   presentation choice and belongs here: colitur's own kernel is pure and
   deliberately never asks what day it is, which is what makes it testable
   to the year 9999. A viewer has no such duty. */
static void select_today(void)
{
	time_t t = time(NULL);
	struct tm tm;
	if (!localtime_r(&t, &tm)) return;
	char iso[11];
	strftime(iso, sizeof iso, "%Y-%m-%d", &tm);
	for (int i = 0; i < nrows; i++)
		if (!strcmp(rows[i].f[0], iso)) { cur = i; return; }
}

/* --- colour helpers ----------------------------------------------------- */
static void alloc(const char *spec, XftColor *c)
{
	XftColorAllocName(dpy, vis, cmap, spec, c);
}

static void colours_for(const char *name, XftColor *bg, XftColor *fg)
{
	for (size_t i = 0; i < sizeof palette / sizeof *palette; i++)
		if (!strcmp(palette[i].name, name)) {
			alloc(palette[i].bg, bg);
			alloc(palette[i].fg, fg);
			return;
		}
	alloc(col_unknown_bg, bg); alloc(col_unknown_fg, fg);
}

static void text(XftColor *c, XftFont *f, int x, int y, const char *s, int maxw)
{
	XGlyphInfo gi;
	int len = strlen(s);
	while (len > 0) {
		XftTextExtentsUtf8(dpy, f, (FcChar8 *)s, len, &gi);
		if (gi.xOff <= maxw) break;
		len--;
	}
	XftDrawStringUtf8(xd, c, f, x, y, (FcChar8 *)s, len);
}

/* An n-pixel ring just inside (x,y,w,h). */
static void ring(XftColor *c, int x, int y, int w, int h, int n)
{
	for (int k = 0; k < n; k++) {
		XftDrawRect(xd, c, x + k,         y + k,         w - 2*k, 1);
		XftDrawRect(xd, c, x + k,         y + h - 1 - k, w - 2*k, 1);
		XftDrawRect(xd, c, x + k,         y + k,         1,       h - 2*k);
		XftDrawRect(xd, c, x + w - 1 - k, y + k,         1,       h - 2*k);
	}
}

static void fill(const char *spec, int x, int y, int w, int h)
{
	XftColor c; alloc(spec, &c);
	XRenderColor rc = c.color;
	XftDrawRect(xd, &c, x, y, w, h);
	(void)rc;
}

/* --- drawing ------------------------------------------------------------ */
static int month_of(int i) { return atoi(rows[i].f[0] + 5); }
static int dom_of(int i)   { return atoi(rows[i].f[0] + 8); }

static int dow_of(int i)
{
	/* Sakamoto, on the ISO date in column 0. */
	static const int t[] = {0,3,2,5,0,3,5,1,4,6,2,4};
	int y = atoi(rows[i].f[0]), m = month_of(i), d = dom_of(i);
	if (m < 3) y--;
	return (y + y/4 - y/100 + y/400 + t[m-1] + d) % 7;
}

/* CX_DUMP=path writes one frame as a PPM and exits. It reads back the
   off-screen PIXMAP, not the window: a window's contents are not retained
   while it is obscured or on an unfocused tag, so screenshotting one can
   return solid black while the program draws perfectly. */
static void dump_and_exit(const char *path, int w, int h)
{
	XImage *im = XGetImage(dpy, buf, 0, 0, w, h, AllPlanes, ZPixmap);
	FILE *f = im ? fopen(path, "wb") : NULL;
	if (!f) { fprintf(stderr, "CX_DUMP: cannot write %s\n", path); exit(1); }
	fprintf(f, "P6\n%d %d\n255\n", w, h);
	for (int y = 0; y < h; y++)
		for (int x = 0; x < w; x++) {
			unsigned long px = XGetPixel(im, x, y);
			unsigned char rgb[3] = { (unsigned char)((px >> 16) & 0xff),
			                         (unsigned char)((px >> 8) & 0xff),
			                         (unsigned char)(px & 0xff) };
			fwrite(rgb, 1, 3, f);
		}
	fclose(f);
	XDestroyImage(im);
	fprintf(stderr, "CX_DUMP: wrote %s (%dx%d)\n", path, w, h);
	exit(0);
}

static void redraw(void)
{
	XWindowAttributes wa;
	XGetWindowAttributes(dpy, win, &wa);
	if (!buf || wa.width != bufw || wa.height != bufh) {
		if (xd)  { XftDrawDestroy(xd); xd = NULL; }
		if (buf) { XFreePixmap(dpy, buf); }
		buf = XCreatePixmap(dpy, win, wa.width, wa.height,
		                    DefaultDepth(dpy, DefaultScreen(dpy)));
		xd = XftDrawCreate(dpy, buf, vis, cmap);
		bufw = wa.width; bufh = wa.height;
	}
	fill(col_bg, 0, 0, wa.width, wa.height);

	/* Cells are sized from the window, not from a constant, so the grid
	   fills its tile. Six rows is the most a month can need: 31 days
	   starting on a Saturday spans six Sunday-started weeks. */
	int CELL_W = (wa.width - 2 * PAD) / 7;
	int CELL_H = (wa.height - HEAD_H - DETAIL_H) / 6;
	if (CELL_W < CELL_W_MIN) CELL_W = CELL_W_MIN;
	if (CELL_H < CELL_H_MIN) CELL_H = CELL_H_MIN;

	XftColor head, detail, sel_dark, sel_light, grid;
	alloc(col_head, &head); alloc(col_detail, &detail);
	alloc(col_sel_dark, &sel_dark); alloc(col_sel_light, &sel_light);
	alloc(col_grid, &grid);

	int mon = month_of(cur);
	char title[128];
	snprintf(title, sizeof title, "%.4s   %02d   %s",
	         rows[cur].f[0], mon, rows[cur].f[3]);
	text(&head, fnt_big, PAD, 26, title, wa.width - 2*PAD);

	for (int c = 0; c < 7; c++)
		text(&head, fnt, PAD + c*CELL_W + 4, HEAD_H - 6, dow_headings[c], CELL_W - 8);

	/* first row index of this month, and where it starts in the week */
	int first = 0;
	while (first < nrows && month_of(first) != mon) first++;
	int slot = dow_of(first);

	for (int i = first; i < nrows && month_of(i) == mon; i++, slot++) {
		int r = slot / 7, c = slot % 7;
		int x = PAD + c*CELL_W, y = HEAD_H + r*CELL_H;

		XftColor bg, fg;
		colours_for(rows[i].f[10], &bg, &fg);
		XftDrawRect(xd, &bg, x, y, CELL_W - 2, CELL_H - 2);
		if (i == cur) {
			/* dark ring outside, bright ring inside: readable on a white
			   cell and on a red one without knowing which it is */
			ring(&sel_dark,  x, y, CELL_W - 2, CELL_H - 2, SEL_RING);
			ring(&sel_light, x + SEL_RING, y + SEL_RING,
			     CELL_W - 2 - 2*SEL_RING, CELL_H - 2 - 2*SEL_RING, SEL_RING);
		}

		int lh    = fnt->ascent + fnt->descent;      /* body line height */
		int bigh  = fnt_big->ascent + fnt_big->descent;
		char d[8]; snprintf(d, sizeof d, "%d", dom_of(i));
		text(&fg, fnt_big, x + 6, y + fnt_big->ascent + 4, d, CELL_W / 3);
		if (!strcmp(rows[i].f[8], badge_rank)) {
			/* badge: filled with the cell's FOREGROUND, glyph in its
			   BACKGROUND, so it inverts against any liturgical colour */
			int gw = 0, bw2, bx, by = y + 4, bh2 = lh + 2;
			XGlyphInfo gi;
			XftTextExtentsUtf8(dpy, fnt, (FcChar8 *)badge_glyph,
			                   strlen(badge_glyph), &gi);
			gw = gi.xOff;
			bw2 = gw + 10;
			bx = x + CELL_W - 4 - bw2;
			XftDrawRect(xd, &fg, bx, by, bw2, bh2);
			XftDrawStringUtf8(xd, &bg, fnt, bx + 5, by + 1 + fnt->ascent,
			                  (FcChar8 *)badge_glyph, strlen(badge_glyph));
		}

		/* Feast name over up to three lines, breaking on spaces that fit
		   the cell. Measured with XftTextExtents rather than guessed at a
		   character count, so it is right for any font in config.h. */
		const char *nm = rows[i].f[6];
		int avail = CELL_W - 12, ty = y + bigh + 8 + fnt->ascent;
		int room = (CELL_H - 2 - (bigh + 8)) / lh;   /* lines that fit */
		if (room > NAME_LINES_MAX) room = NAME_LINES_MAX;
		if (room < 1) room = 1;
		const char *p = nm;
		for (int ln = 0; ln < room && *p; ln++) {
			size_t take = strlen(p), best = 0;
			XGlyphInfo gi;
			for (size_t k = 1; k <= take; k++) {
				XftTextExtentsUtf8(dpy, fnt, (FcChar8 *)p, k, &gi);
				if (gi.xOff > avail) break;
				if (p[k] == ' ' || p[k] == 0) best = k;
			}
			if (!best) {                      /* one long word: hard cut */
				for (size_t k = 1; k <= take; k++) {
					XftTextExtentsUtf8(dpy, fnt, (FcChar8 *)p, k, &gi);
					if (gi.xOff > avail) { best = k ? k - 1 : 1; break; }
					best = k;
				}
			}
			XftDrawStringUtf8(xd, &fg, fnt, x + 6, ty, (FcChar8 *)p, best);
			ty += lh;
			p += best;
			while (*p == ' ') p++;
		}
	}

	int dy = wa.height - DETAIL_H;
	XftDrawRect(xd, &grid, 0, dy - 1, wa.width, 1);
	char line[512];
	snprintf(line, sizeof line, "%s   %s", rows[cur].f[0], rows[cur].f[6]);
	text(&detail, fnt_big, PAD, dy + 22, line, wa.width - 2*PAD);
	snprintf(line, sizeof line, "%s  ·  %s", rows[cur].f[9], rows[cur].f[11]);
	text(&head, fnt, PAD, dy + 42, line, wa.width - 2*PAD);
	snprintf(line, sizeof line, "%-10s %s", label_epistle, rows[cur].f[13]);
	text(&detail, fnt, PAD, dy + 62, line, wa.width - 2*PAD);
	snprintf(line, sizeof line, "%-10s %s", label_gospel, rows[cur].f[14]);
	text(&detail, fnt, PAD, dy + 80, line, wa.width - 2*PAD);

	XCopyArea(dpy, buf, win, gc, 0, 0, wa.width, wa.height, 0, 0);
	{
		const char *p = getenv("CX_DUMP");
		if (p) dump_and_exit(p, wa.width, wa.height);
	}
}

static void usage(void)
{
	fputs("usage: colitur-x [-g WxH] < calendar.csv\n", stderr);
	exit(2);
}

int main(int argc, char **argv)
{
	int w = WIN_W, h = WIN_H;
	for (int i = 1; i < argc; i++) {
		if (!strcmp(argv[i], "-g") && i + 1 < argc) {
			if (sscanf(argv[++i], "%dx%d", &w, &h) != 2) usage();
		} else usage();
	}
	load();
	if (!nrows) { fputs("colitur-x: no rows on stdin\n", stderr); return 2; }
	select_today();

	if (!(dpy = XOpenDisplay(NULL))) { fputs("cannot open display\n", stderr); return 1; }
	scr = DefaultScreen(dpy);
	vis = DefaultVisual(dpy, scr);
	cmap = DefaultColormap(dpy, scr);

	win = XCreateSimpleWindow(dpy, RootWindow(dpy, scr), 0, 0, w, h, 0,
	                          BlackPixel(dpy, scr), BlackPixel(dpy, scr));
	XStoreName(dpy, win, window_title);
	{	/* A PREFERRED size and a MINIMUM, never a fixed one. Pinning the
		   size was the earlier mistake: it fights a tiling window manager,
		   which ignores it anyway, and it stops the grid making use of a
		   larger tile. The layout reflows, so any size above the minimum
		   is legitimate. */
		XSizeHints *sh = XAllocSizeHints();
		sh->flags = PSize | PMinSize;
		sh->width = w; sh->height = h;
		sh->min_width  = PAD*2 + 7*CELL_W_MIN;
		sh->min_height = HEAD_H + 6*CELL_H_MIN + DETAIL_H;
		XSetWMNormalHints(dpy, win, sh);
		XFree(sh);
	}
	XSelectInput(dpy, win, ExposureMask | KeyPressMask | StructureNotifyMask);
	XMapWindow(dpy, win);

	fnt     = XftFontOpenName(dpy, scr, font);
	fnt_big = XftFontOpenName(dpy, scr, font_big);
	gc      = XCreateGC(dpy, win, 0, NULL);
	/* xd is created against the off-screen pixmap in redraw() */

	for (XEvent ev;;) {
		XNextEvent(dpy, &ev);
		if (ev.type == Expose || ev.type == ConfigureNotify) redraw();
		else if (ev.type == KeyPress) {
			KeySym k = XLookupKeysym(&ev.xkey, 0);
			int mon = month_of(cur);
			if (k == XK_q) break;
			else if (k == XK_Right || k == XK_l) cur = (cur + 1) % nrows;
			else if (k == XK_Left  || k == XK_h) cur = (cur + nrows - 1) % nrows;
			else if (k == XK_Down  || k == XK_j) cur = (cur + 7) % nrows;
			else if (k == XK_Up    || k == XK_k) cur = (cur + nrows - 7) % nrows;
			else if (k == XK_n) { while (cur < nrows-1 && month_of(cur) == mon) cur++; }
			else if (k == XK_p) { while (cur > 0 && month_of(cur) == mon) cur--;
			                      mon = month_of(cur);
			                      while (cur > 0 && month_of(cur-1) == mon) cur--; }
			redraw();
		}
	}
	XCloseDisplay(dpy);
	return 0;
}