import { CONTEXT_DISPLAY_MODE_VALUES, CONTEXT_UNKNOWN_MODE_VALUES } from "./config-options.js";
import type { SegmentFeature } from "./segment-feature.js";
import type { GlanceConfig, SegmentData, SegmentRenderContext } from "./types.js";

const CONTEXT_DISPLAY_LABELS: Record<GlanceConfig["context"]["display"], string> = {
	"percent+tokens": "percent / tokens",
	percent: "percent",
	tokens: "tokens",
};

function nextIn<T extends string | number>(current: T, values: readonly T[]): T {
	const index = values.indexOf(current);
	return values[(index + 1) % values.length] ?? values[0]!;
}

function formatTokens(count: number | null | undefined): string {
	if (count === null || count === undefined || !Number.isFinite(count)) return "?";
	const abs = Math.abs(count);
	if (abs < 1000) return `${Math.round(count)}`;
	if (abs < 10_000) return `${(count / 1000).toFixed(1)}k`;
	if (abs < 1_000_000) return `${Math.round(count / 1000)}k`;
	if (abs < 10_000_000) return `${(count / 1_000_000).toFixed(1)}M`;
	return `${Math.round(count / 1_000_000)}M`;
}

function formatPercent(percent: number | null | undefined): string {
	if (percent === null || percent === undefined || !Number.isFinite(percent)) return "?";
	return percent >= 10 ? `${percent.toFixed(0)}%` : `${percent.toFixed(1)}%`;
}

function contextDisplayLabel(mode: GlanceConfig["context"]["display"]): string {
	return CONTEXT_DISPLAY_LABELS[mode];
}

function contextTokenRatio(ctx: SegmentRenderContext): string {
	return `${formatTokens(ctx.state.context.tokens)}/${formatTokens(ctx.state.context.window)}`;
}

function contextIsUnknown(ctx: SegmentRenderContext): boolean {
	return ctx.state.context.percent === null && ctx.state.context.tokens === null;
}

function contextDisplayValue(ctx: SegmentRenderContext): string {
	const pct = formatPercent(ctx.state.context.percent);
	const ratio = contextTokenRatio(ctx);
	if (ctx.config.context.display === "percent") return pct;
	if (ctx.config.context.display === "tokens") return ratio;
	return `${pct} ${ratio}`;
}

function contextCompactValue(ctx: SegmentRenderContext): string {
	if (ctx.config.context.display === "tokens") return contextTokenRatio(ctx);
	return formatPercent(ctx.state.context.percent);
}

function collectContext(ctx: SegmentRenderContext): SegmentData | undefined {
	if (ctx.config.context.unknown === "hide" && contextIsUnknown(ctx)) return undefined;
	const primary = ctx.config.context.display === "tokens" ? contextTokenRatio(ctx) : formatPercent(ctx.state.context.percent);
	const secondary = ctx.config.context.display === "percent+tokens" ? contextTokenRatio(ctx) : undefined;
	const compact = contextCompactValue(ctx);
	return {
		primary,
		secondary,
		display: {
			full: contextDisplayValue(ctx),
			compact,
			minimal: compact,
		},
	};
}

export const contextSegmentFeature = {
	id: "context",
	label: "Context",
	defaultEnabled: true,
	settings: [
		{
			id: "context.display",
			label: "Display",
			hint: "Choose percent, tokens, or both.",
			kind: "cycle",
			value: (config: GlanceConfig) => contextDisplayLabel(config.context.display),
			mutate: (config: GlanceConfig) => {
				config.context.display = nextIn(config.context.display, CONTEXT_DISPLAY_MODE_VALUES);
			},
		},
		{
			id: "context.unknown",
			label: "Unknown",
			hint: "Show ? or hide when context is unknown.",
			kind: "cycle",
			value: (config: GlanceConfig) => config.context.unknown,
			mutate: (config: GlanceConfig) => {
				config.context.unknown = nextIn(config.context.unknown, CONTEXT_UNKNOWN_MODE_VALUES);
			},
		},
	],
	collect: collectContext,
} as const satisfies SegmentFeature;