/**
 * markdown-it plugin that normalizes measurements to metric at build time
 * and wraps them in <span> elements with pre-computed metric/imperial text
 * for client-side toggling.
 *
 * Default display: metric units, collapsed times
 * Toggle: imperial units, expanded times
 */

const { findAllMeasurements } = require('./matcher');

// ─── Number Formatting ──────────────────────────────────

function formatNumber(n) {
  if (Number.isInteger(n) || Math.abs(n - Math.round(n)) < 0.001) {
    return Math.round(n).toString();
  }
  const decimals = Math.abs(n) >= 10 ? 1 : 2;
  return n.toFixed(decimals).replace(/\.?0+$/, '');
}

// ─── Unit Display ───────────────────────────────────────

// Units that get no space before them
const NO_SPACE_UNITS = new Set(['g', 'kg', 'ml', '°C', '°F', 'cm', 'mm']);

function unitLabel(unit, plural) {
  const labels = {
    'g': 'g', 'kg': 'kg', 'oz': 'oz', 'lb': 'lb',
    'cup': plural ? 'cups' : 'cup',
    'tablespoon': 'tbsp', 'teaspoon': 'tsp',
    'ml': 'ml', 'L': 'L',
    'quart': plural ? 'quarts' : 'quart',
    'gallon': plural ? 'gallons' : 'gallon',
    'pint': plural ? 'pints' : 'pint',
    'fl oz': 'fl oz',
    '°F': '°F', '°C': '°C',
    'inch': plural ? 'inches' : 'inch',
    'cm': 'cm', 'mm': 'mm',
    'minute': 'min', 'hour': 'hr', 'day': plural ? 'days' : 'day',
    'second': plural ? 'seconds' : 'sec',
    'parts by volume': 'parts by volume',
    'parts by weight': 'parts by weight',
  };
  return labels[unit] || unit;
}

function formatValueUnit(value, unit) {
  const label = unitLabel(unit, value !== 1);
  const space = NO_SPACE_UNITS.has(unit) ? '' : ' ';
  return formatNumber(value) + space + label;
}

// ─── Conversion Helpers ─────────────────────────────────

function roundTemp(v) {
  return Math.round(v / 5) * 5;
}

function smartMetricWeight(grams) {
  if (grams >= 1000) return { value: grams / 1000, unit: 'kg' };
  return { value: grams, unit: 'g' };
}

function smartImperialWeight(oz) {
  if (oz >= 16) return { value: oz / 16, unit: 'lb' };
  return { value: oz, unit: 'oz' };
}

function smartMetricVolume(ml) {
  if (ml >= 1000) return { value: ml / 1000, unit: 'L' };
  return { value: ml, unit: 'ml' };
}

function smartImperialVolume(ml) {
  if (ml >= 236.588) return { value: ml / 236.588, unit: 'cup' };
  if (ml >= 14.787) return { value: ml / 14.787, unit: 'tablespoon' };
  return { value: ml / 4.929, unit: 'teaspoon' };
}

// Convert a single value from one unit to metric
function toMetricValue(value, unit) {
  switch (unit) {
    // Temperature
    case '°F': return { value: roundTemp((value - 32) * 5 / 9), unit: '°C' };
    case '°C': return { value, unit: '°C' };
    // Weight
    case 'oz': return smartMetricWeight(value * 28.3495);
    case 'lb': return smartMetricWeight(value * 453.592);
    case 'g':  return smartMetricWeight(value);
    case 'kg': return smartMetricWeight(value * 1000);
    // Volume
    case 'cup':        return smartMetricVolume(value * 236.588);
    case 'tablespoon': return smartMetricVolume(value * 14.787);
    case 'teaspoon':   return smartMetricVolume(value * 4.929);
    case 'quart':      return smartMetricVolume(value * 946.353);
    case 'gallon':     return smartMetricVolume(value * 3785.41);
    case 'pint':       return smartMetricVolume(value * 473.176);
    case 'fl oz':      return smartMetricVolume(value * 29.5735);
    case 'ml':         return smartMetricVolume(value);
    case 'L':          return smartMetricVolume(value * 1000);
    // Dimension
    case 'inch': return { value: value * 2.54, unit: 'cm' };
    case 'cm':   return { value, unit: 'cm' };
    case 'mm':   return { value, unit: 'mm' };
    default:     return { value, unit };
  }
}

// Convert a single value from one unit to imperial
function toImperialValue(value, unit) {
  switch (unit) {
    // Temperature
    case '°C': return { value: roundTemp(value * 9 / 5 + 32), unit: '°F' };
    case '°F': return { value, unit: '°F' };
    // Weight
    case 'g':  return smartImperialWeight(value / 28.3495);
    case 'kg': return smartImperialWeight(value * 2.20462 * 16); // kg→oz then smart
    case 'oz': return smartImperialWeight(value);
    case 'lb': return smartImperialWeight(value * 16);
    // Volume
    case 'ml':         return smartImperialVolume(value);
    case 'L':          return smartImperialVolume(value * 1000);
    case 'cup':        return { value, unit: 'cup' };
    case 'tablespoon': return { value, unit: 'tablespoon' };
    case 'teaspoon':   return { value, unit: 'teaspoon' };
    case 'quart':      return { value, unit: 'quart' };
    case 'gallon':     return { value, unit: 'gallon' };
    case 'pint':       return { value, unit: 'pint' };
    case 'fl oz':      return { value, unit: 'fl oz' };
    // Dimension
    case 'cm':   return { value: value / 2.54, unit: 'inch' };
    case 'mm':   return { value: value / 25.4, unit: 'inch' };
    case 'inch': return { value, unit: 'inch' };
    default:     return { value, unit };
  }
}

// ─── Base Unit Conversion (for scaling) ─────────────────

function toBaseGrams(value, unit) {
  switch (unit) {
    case 'g':  return value;
    case 'kg': return value * 1000;
    case 'oz': return value * 28.3495;
    case 'lb': return value * 453.592;
    default:   return value;
  }
}

function toBaseMl(value, unit) {
  switch (unit) {
    case 'ml':         return value;
    case 'L':          return value * 1000;
    case 'cup':        return value * 236.588;
    case 'tablespoon': return value * 14.787;
    case 'teaspoon':   return value * 4.929;
    case 'quart':      return value * 946.353;
    case 'gallon':     return value * 3785.41;
    case 'pint':       return value * 473.176;
    case 'fl oz':      return value * 29.5735;
    default:           return value;
  }
}

function computeScaleData(measurement) {
  const { type, amount, unit, approximate } = measurement;
  if (unit === 'parts by volume' || unit === 'parts by weight') return null;
  if (type !== 'weight' && type !== 'volume' && type !== 'count') return null;

  if (type === 'count') {
    if (amount.min !== undefined) {
      return {
        base: [amount.min.value, amount.max.value],
        type: 'count',
        approx: approximate || amount.min.approximate || false,
      };
    }
    return {
      base: amount.value,
      type: 'count',
      approx: approximate || false,
    };
  }

  const toBase = type === 'weight' ? toBaseGrams : toBaseMl;

  if (amount.min !== undefined) {
    return {
      base: [toBase(amount.min.value, unit), toBase(amount.max.value, unit)],
      type: type,
      approx: approximate || amount.min.approximate || false,
    };
  }

  return {
    base: toBase(amount.value, unit),
    type: type,
    approx: approximate || false,
  };
}

// ─── Time Formatting ────────────────────────────────────

function toMinutes(value, unit) {
  if (unit === 'minute') return value;
  if (unit === 'hour') return value * 60;
  if (unit === 'second') return value / 60;
  return null; // days stay as-is
}

function collapsedTime(value, unit) {
  if (unit === 'day') return formatValueUnit(value, 'day');
  if (unit === 'second') return formatValueUnit(value, 'second');
  const mins = toMinutes(value, unit);
  if (mins === null) return formatValueUnit(value, unit);
  return formatValueUnit(mins, 'minute');
}

function expandedTime(value, unit) {
  if (unit === 'day') return formatValueUnit(value, 'day');
  if (unit === 'second') return formatValueUnit(value, 'second');
  const mins = toMinutes(value, unit);
  if (mins === null) return formatValueUnit(value, unit);
  if (mins < 60) return formatValueUnit(mins, 'minute');
  const hours = Math.floor(mins / 60);
  const remainder = Math.round(mins % 60);
  if (remainder === 0) {
    return hours + (hours === 1 ? ' hour' : ' hours');
  }
  return hours + ' hr ' + remainder + ' min';
}

// ─── Text Generation ────────────────────────────────────

function formatSingleConverted(val, unit, approximate) {
  const prefix = approximate ? '~' : '';
  return prefix + formatValueUnit(val, unit);
}

function generateTexts(measurement) {
  const { type, amount, unit, approximate } = measurement;

  // Non-convertible units
  if (unit === 'parts by volume' || unit === 'parts by weight') {
    const text = formatMeasurementText(amount, unit, approximate);
    return { defaultText: text, altText: text };
  }

  // Bare counts — just display the number, no conversion
  if (type === 'count') {
    const text = formatCountText(amount, approximate);
    return { defaultText: text, altText: text };
  }

  if (type === 'time') {
    return generateTimeTexts(amount, unit, approximate);
  }

  return generateUnitTexts(amount, unit, approximate, type);
}

function formatCountText(amount, approximate) {
  const prefix = approximate ? '~' : '';
  if (amount.min !== undefined) {
    return prefix + formatNumber(amount.min.value) + '-' + formatNumber(amount.max.value);
  }
  return prefix + formatNumber(amount.value);
}

function generateTimeTexts(amount, unit, approximate) {
  if (amount.min !== undefined) {
    const prefix = amount.min.approximate ? '~' : '';
    const defText = prefix + collapsedTime(amount.min.value, unit) + '-' + collapsedTime(amount.max.value, unit);
    const altText = prefix + expandedTime(amount.min.value, unit) + ' to ' + expandedTime(amount.max.value, unit);
    return { defaultText: defText, altText: altText };
  }
  const prefix = approximate ? '~' : '';
  return {
    defaultText: prefix + collapsedTime(amount.value, unit),
    altText: prefix + expandedTime(amount.value, unit),
  };
}

function generateUnitTexts(amount, unit, approximate, type) {
  if (type === 'dimension' && Array.isArray(amount)) {
    return generateDimensionTexts(amount, unit);
  }

  if (amount.min !== undefined) {
    return generateRangeTexts(amount, unit, type);
  }

  // Single value
  const metric = toMetricValue(amount.value, unit);
  const imperial = toImperialValue(amount.value, unit);
  const prefix = approximate ? '~' : '';
  return {
    defaultText: prefix + formatValueUnit(metric.value, metric.unit),
    altText: prefix + formatValueUnit(imperial.value, imperial.unit),
  };
}

function generateRangeTexts(amount, unit, type) {
  const mMin = toMetricValue(amount.min.value, unit);
  const mMax = toMetricValue(amount.max.value, unit);
  const iMin = toImperialValue(amount.min.value, unit);
  const iMax = toImperialValue(amount.max.value, unit);
  const prefix = amount.min.approximate ? '~' : '';

  let defaultText, altText;

  if (mMin.unit === mMax.unit) {
    const space = NO_SPACE_UNITS.has(mMin.unit) ? '' : ' ';
    defaultText = prefix + formatNumber(mMin.value) + '-' + formatNumber(mMax.value) + space + unitLabel(mMin.unit, mMax.value !== 1);
  } else {
    defaultText = prefix + formatValueUnit(mMin.value, mMin.unit) + '-' + formatValueUnit(mMax.value, mMax.unit);
  }

  if (iMin.unit === iMax.unit) {
    const space = NO_SPACE_UNITS.has(iMin.unit) ? '' : ' ';
    altText = prefix + formatNumber(iMin.value) + '-' + formatNumber(iMax.value) + space + unitLabel(iMin.unit, iMax.value !== 1);
  } else {
    altText = prefix + formatValueUnit(iMin.value, iMin.unit) + '-' + formatValueUnit(iMax.value, iMax.unit);
  }

  return { defaultText, altText };
}

function generateDimensionTexts(dims, unit) {
  const metricDims = dims.map(d => {
    const c = toMetricValue(d, unit || 'inch');
    return c;
  });
  const imperialDims = dims.map(d => {
    const c = toImperialValue(d, unit || 'inch');
    return c;
  });

  const mUnit = metricDims[0].unit;
  const iUnit = imperialDims[0].unit;

  const defaultText = metricDims.map(d => formatNumber(d.value)).join('x') +
    (mUnit ? (NO_SPACE_UNITS.has(mUnit) ? '' : ' ') + unitLabel(mUnit, true) : '');
  const altText = imperialDims.map(d => formatNumber(d.value)).join('x') +
    (iUnit ? (NO_SPACE_UNITS.has(iUnit) ? '' : ' ') + unitLabel(iUnit, true) : '');

  return { defaultText, altText };
}

function formatMeasurementText(amount, unit, approximate) {
  const prefix = approximate ? '~' : '';
  if (amount.min !== undefined) {
    return prefix + formatValueUnit(amount.min.value, unit) + '-' + formatValueUnit(amount.max.value, unit);
  }
  return prefix + formatValueUnit(amount.value, unit);
}

// ─── Token Replacement ──────────────────────────────────

function replaceMeasurementsInToken(token, Token) {
  const text = token.content;
  const measurements = findAllMeasurements(text);

  if (measurements.length === 0) return [token];

  const newTokens = [];
  let lastEnd = 0;

  for (const m of measurements) {
    // Add text before this measurement
    if (m.index > lastEnd) {
      const before = new Token('text', '', 0);
      before.content = text.slice(lastEnd, m.index);
      newTokens.push(before);
    }

    const { defaultText, altText } = generateTexts(m);

    // Open span
    const open = new Token('measurement_open', 'span', 1);
    open.attrSet('class', 'measurement');
    open.attrSet('data-measurement-type', m.type);
    open.attrSet('data-default', defaultText);
    open.attrSet('data-alt', altText);
    open.attrSet('title', m.match);

    // Add scaling data for weight/volume
    const scaleData = computeScaleData(m);
    if (scaleData) {
      open.attrSet('data-scalable', JSON.stringify(scaleData));
    }

    newTokens.push(open);

    // Display metric-normalized text by default
    const content = new Token('text', '', 0);
    content.content = defaultText;
    newTokens.push(content);

    // Close span
    const close = new Token('measurement_close', 'span', -1);
    newTokens.push(close);

    lastEnd = m.index + m.match.length;
  }

  // Remaining text after last measurement
  if (lastEnd < text.length) {
    const after = new Token('text', '', 0);
    after.content = text.slice(lastEnd);
    newTokens.push(after);
  }

  return newTokens;
}

// ─── Plugin Entry Point ─────────────────────────────────

function measurementPlugin(md) {
  md.core.ruler.push('measurements', function measurementRule(state) {
    const tokens = state.tokens;

    for (let i = 0; i < tokens.length; i++) {
      if (tokens[i].type !== 'inline' || !tokens[i].children) continue;

      const children = tokens[i].children;
      const newChildren = [];

      for (const child of children) {
        if (child.type === 'text') {
          const replaced = replaceMeasurementsInToken(child, state.Token);
          newChildren.push(...replaced);
        } else {
          newChildren.push(child);
        }
      }

      tokens[i].children = newChildren;
    }
  });
}

module.exports = measurementPlugin;

// Exported for testing
module.exports.formatNumber = formatNumber;
module.exports.toMetricValue = toMetricValue;
module.exports.toImperialValue = toImperialValue;
module.exports.generateTexts = generateTexts;
module.exports.collapsedTime = collapsedTime;
module.exports.expandedTime = expandedTime;