import type { ThemeColor } from "@earendil-works/pi-coding-agent";

/** Cap on sub-items listed per section in the overview. */
export const MAX_LISTED = 5;

/** Compact number formatting: 1.50M / 12.3k / 42. */
export const fmt = (n: number): string => {
	if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(2)}M`;
	if (n >= 1_000) return `${(n / 1_000).toFixed(1)}k`;
	return `${Math.round(n)}`;
};

/** Token count as a percentage of the window (0 when window is unknown). */
export const percent = (tokens: number, window: number): number =>
	window > 0 ? (tokens / window) * 100 : 0;

/** Theme color for a token count relative to the window + compaction threshold. */
export const themeColorFor = (
	tokens: number,
	window: number,
	threshold: number,
): ThemeColor => {
	const p = percent(tokens, window);
	if (tokens >= threshold || p >= 95) return "error";
	if (p >= 75) return "warning";
	if (p >= 50) return "accent";
	return "success";
};

/** ASCII progress bar with a `┃` marker at the compaction threshold. */
export const bar = (tokens: number, window: number, threshold: number, width = 20): string => {
	const p = percent(tokens, window);
	const filled = Math.round((p / 100) * width);
	const thresholdPos = Math.min(
		Math.round((Math.min(threshold, window) / window) * width),
		width - 1,
	);
	const cells: string[] = Array.from({ length: width }, (_, i) =>
		i < filled ? "█" : "░",
	);
	if (thresholdPos >= 0) cells[thresholdPos] = "┃";
	return cells.join("");
};

/** Compact "a 2.1k · b 1.1k · +3 more" list, largest first, capped. */
export const compactList = (
	items: { label: string; tokens: number }[],
	cap = MAX_LISTED,
): string => {
	const sorted = [...items].sort((a, b) => b.tokens - a.tokens);
	const shown = sorted.slice(0, cap);
	const rest = sorted.length - shown.length;
	const parts = shown.map((i) => `${i.label} ${fmt(i.tokens)}`);
	if (rest > 0) parts.push(`+${rest} more`);
	return parts.join(" · ");
};