'use strict';

/**
 * Context-utilization classifier for `gsd-health --context`.
 *
 * Pure function. Callers pass tokensUsed + contextWindow; the
 * classifier returns the percent and one of three states. Recommendation
 * strings are NOT in this module — formatting is the renderer's job
 * (see `validate context` in gsd-tools.cjs). That separation lets the
 * copy change without touching this module's tests.
 *
 * Thresholds:
 *   < 60%   healthy   no action
 *   60–70%  warning   approaching the fracture zone
 *   ≥ 70%   critical  reasoning quality may degrade
 *
 * State boundaries use the exact ratio. The displayed `percent` is
 * rounded for human reading and may differ from the boundary by ±1 in
 * edge cases (e.g. 59.999% displays as 60 but classifies as healthy).
 */

const STATES = Object.freeze({
  HEALTHY: 'healthy',
  WARNING: 'warning',
  CRITICAL: 'critical',
});

function classifyContextUtilization(tokensUsed, contextWindow) {
  if (!Number.isInteger(tokensUsed) || tokensUsed < 0) {
    throw new TypeError(`tokensUsed must be a non-negative integer, got: ${tokensUsed} (${typeof tokensUsed})`);
  }
  if (!Number.isInteger(contextWindow) || contextWindow <= 0) {
    throw new TypeError(`contextWindow must be a positive integer, got: ${contextWindow} (${typeof contextWindow})`);
  }

  const ratio = Math.min(tokensUsed / contextWindow, 1);
  const percent = Math.min(Math.round(ratio * 100), 100);

  let state;
  if (ratio < 0.60) state = STATES.HEALTHY;
  else if (ratio < 0.70) state = STATES.WARNING;
  else state = STATES.CRITICAL;

  return { percent, state };
}

module.exports = { classifyContextUtilization, STATES };