import { cn } from "@/shared/lib/cn";
import { Tooltip, TooltipContent, TooltipTrigger } from "@/shared/ui/tooltip";

const WEEK_COUNT = 26;
const DAYS_PER_WEEK = 7;

// Intensity ramp shared by the cells and the legend dots.
// Tints of the theme's primary token: the most active cells are fully
// saturated primary, quieter days fade toward the muted background.
const LEVEL_CLASSES = [
  "bg-muted/40 dark:bg-muted/30",
  "bg-primary/25",
  "bg-primary/50",
  "bg-primary/75",
  "bg-primary",
];

// Descriptors matching the thresholds in `levelFor`.
const LEVEL_LABELS = [
  "No activity",
  "1–2 events",
  "3–5 events",
  "6–9 events",
  "10+ events",
];

/** Activity intensity legend shared with the contribution graph header. */
export function ProjectsContributionLegend() {
  return (
    <div className="flex items-center gap-1.5">
      {LEVEL_CLASSES.map((levelClass, level) => (
        <Tooltip key={levelClass}>
          <TooltipTrigger asChild>
            <span className={cn("h-2.5 w-2.5 rounded", levelClass)} />
          </TooltipTrigger>
          <TooltipContent>{LEVEL_LABELS[level]}</TooltipContent>
        </Tooltip>
      ))}
    </div>
  );
}

function dayKeyOf(date: Date) {
  const month = `${date.getMonth() + 1}`.padStart(2, "0");
  const day = `${date.getDate()}`.padStart(2, "0");
  return `${date.getFullYear()}-${month}-${day}`;
}

function levelFor(count: number) {
  if (count <= 0) return 0;
  if (count <= 2) return 1;
  if (count <= 5) return 2;
  if (count <= 9) return 3;
  return 4;
}

/** Week columns (each 7 days, Sunday first) ending with the current week. */
function buildWeeks(today: Date, weekCount: number) {
  const start = new Date(
    today.getFullYear(),
    today.getMonth(),
    today.getDate() - today.getDay() - (weekCount - 1) * DAYS_PER_WEEK,
  );

  return Array.from({ length: weekCount }, (_, weekIndex) =>
    Array.from({ length: DAYS_PER_WEEK }, (_, dayIndex) => {
      const date = new Date(start);
      date.setDate(start.getDate() + weekIndex * DAYS_PER_WEEK + dayIndex);
      return date;
    }),
  );
}

// Minimum columns between labels so adjacent months never overlap.
const MIN_LABEL_GAP = 3;

function monthLabels(weeks: Date[][]) {
  let lastLabeledIndex = -MIN_LABEL_GAP;
  return weeks.map((week, index) => {
    const isNewMonth =
      index === 0 || week[0].getMonth() !== weeks[index - 1][0].getMonth();
    if (!isNewMonth || index - lastLabeledIndex < MIN_LABEL_GAP) return "";
    lastLabeledIndex = index;
    return week[0].toLocaleDateString(undefined, { month: "short" });
  });
}

/**
 * GitHub-style activity heatmap for the last 26 weeks, fed by per-day
 * activity counts (see `ProjectActivitySummary.activityByDay`).
 */
export function ProjectsContributionGraph({
  activityByDay,
  className,
  compact = false,
}: {
  activityByDay: Record<string, number>;
  className?: string;
  compact?: boolean;
}) {
  const today = new Date();
  const weeks = buildWeeks(today, compact ? 18 : WEEK_COUNT);
  const labels = monthLabels(weeks);
  const gridTemplateColumns = `repeat(${weeks.length}, minmax(0, 1fr))`;
  const todayKey = dayKeyOf(today);

  return (
    <div className={cn("space-y-2", className)}>
      <div
        className={cn("grid", compact ? "gap-1" : "gap-2")}
        style={{ gridTemplateColumns }}
      >
        {labels.map((label, index) => (
          <span
            className="overflow-visible whitespace-nowrap text-2xs font-medium text-muted-foreground"
            // Columns are positional; labels have no stable content key.
            // biome-ignore lint/suspicious/noArrayIndexKey: fixed-size grid
            key={index}
          >
            {label}
          </span>
        ))}
      </div>
      <div
        className={cn(
          "grid grid-flow-col grid-rows-7",
          compact ? "gap-1" : "gap-2",
        )}
        style={{ gridTemplateColumns }}
      >
        {weeks.map((week) =>
          week.map((day) => {
            const key = dayKeyOf(day);
            if (key > todayKey) {
              return (
                <span
                  aria-hidden
                  className="aspect-square rounded-[22%] border border-border/40 dark:border-border/30"
                  key={key}
                />
              );
            }
            const count = activityByDay[key] ?? 0;
            const dateLabel = day.toLocaleDateString(undefined, {
              month: "short",
              day: "numeric",
            });
            return (
              <Tooltip key={key}>
                <TooltipTrigger asChild>
                  <span
                    className={cn(
                      "aspect-square w-full rounded-[22%]",
                      LEVEL_CLASSES[levelFor(count)],
                    )}
                  />
                </TooltipTrigger>
                <TooltipContent>
                  {count > 0
                    ? `${count} ${count === 1 ? "event" : "events"} · ${dateLabel}`
                    : `No activity · ${dateLabel}`}
                </TooltipContent>
              </Tooltip>
            );
          }),
        )}
      </div>
    </div>
  );
}