// Helpers for the per-pane context-fill indicator. Context occupancy (token
// count) comes from the backend (src-tauri/src/usage.rs, get_pane_context); this
// turns it into a window %, a colour, and a human label.

import type { SessionContext } from "../ipc";

const WINDOW_LARGE = 1_000_000;

/**
 * Assumed context window. The transcript does NOT record whether a session
 * runs the 200k or 1M window (the model id is bare, e.g. `claude-opus-4-7` —
 * the `[1m]` that claude's /context shows is display-only), so the % can't be
 * computed reliably. We assume 1M (the common case here) for the fill bar, and
 * the indicator LABEL shows the absolute token count, which is accurate
 * regardless of the real window — that's the figure to trust.
 */
export function contextWindow(_contextTokens: number): number {
  return WINDOW_LARGE;
}

/** Fraction (0..1) of the inferred window currently occupied. */
export function contextFraction(s: SessionContext): number {
  const w = contextWindow(s.contextTokens);
  return w > 0 ? Math.min(1, s.contextTokens / w) : 0;
}

export function contextPercent(s: SessionContext): number {
  return Math.round(contextFraction(s) * 100);
}

/** Green → amber → red ramp as the window fills. */
export function contextColor(fraction: number): string {
  if (fraction >= 0.85) return "#d65a5a";
  if (fraction >= 0.6) return "#d6a23a";
  return "#5aa84a";
}

export function formatTokens(n: number): string {
  if (n >= 1_000_000) return (n / 1_000_000).toFixed(1) + "M";
  if (n >= 1_000) return Math.round(n / 1_000) + "k";
  return String(n);
}

/** e.g. "274k tokens · ~27% of 1M (last turn)" for a tooltip. */
export function contextLabel(s: SessionContext): string {
  return `${formatTokens(s.contextTokens)} tokens · ~${contextPercent(s)}% of 1M (last turn)`;
}