/**
 * Plain-language metric labels and explanations.
 * Single source of truth for all metric display strings.
 */

export interface MetricExplanation {
  label: string;
  plain: string;
  detail?: string;
}

export const METRIC_EXPLANATIONS: Record<string, MetricExplanation> = {
  rwm_expected_pct: {
    label: 'Reading, Writing & Maths',
    plain: '% of pupils achieving the expected standard in all three subjects at age 11',
    detail: 'The national average is around 60%. Higher means more pupils reached the expected level.',
  },
  rwm_high_pct: {
    label: 'Higher Standard — Reading, Writing & Maths',
    plain: '% of pupils exceeding the expected level in all three subjects',
    detail: 'A more demanding threshold. The national average is around 8%.',
  },
  reading_expected_pct: {
    label: 'Reading — Expected Standard',
    plain: '% of pupils achieving the expected standard in reading at age 11',
  },
  writing_expected_pct: {
    label: 'Writing — Expected Standard',
    plain: '% of pupils achieving the expected standard in writing at age 11',
  },
  maths_expected_pct: {
    label: 'Maths — Expected Standard',
    plain: '% of pupils achieving the expected standard in maths at age 11',
  },
  reading_high_pct: {
    label: 'Reading — Higher Standard',
    plain: '% of pupils exceeding the expected level in reading',
  },
  writing_high_pct: {
    label: 'Writing — Higher Standard',
    plain: '% of pupils exceeding the expected level in writing',
  },
  maths_high_pct: {
    label: 'Maths — Higher Standard',
    plain: '% of pupils exceeding the expected level in maths',
  },
  gps_expected_pct: {
    label: 'Grammar & Spelling',
    plain: '% of pupils achieving the expected standard in grammar, punctuation & spelling',
  },
  science_expected_pct: {
    label: 'Science',
    plain: '% of pupils achieving the expected standard in science',
  },
  reading_progress: {
    label: 'Reading Progress',
    plain: 'How much pupils improved in reading compared to similar schools',
    detail: '0 = national average. Positive means better-than-average progress from Year 2 to Year 6.',
  },
  writing_progress: {
    label: 'Writing Progress',
    plain: 'How much pupils improved in writing compared to similar schools',
    detail: '0 = national average. Positive means better-than-average progress from Year 2 to Year 6.',
  },
  maths_progress: {
    label: 'Maths Progress',
    plain: 'How much pupils improved in maths compared to similar schools',
    detail: '0 = national average. Positive means better-than-average progress from Year 2 to Year 6.',
  },
  reading_avg_score: {
    label: 'Reading Average Score',
    plain: 'Average scaled score in the reading test (range 80–120, average = 100)',
  },
  maths_avg_score: {
    label: 'Maths Average Score',
    plain: 'Average scaled score in the maths test (range 80–120, average = 100)',
  },
  gps_avg_score: {
    label: 'Grammar & Spelling Average Score',
    plain: 'Average scaled score in the grammar, punctuation & spelling test',
  },
  overall_absence_pct: {
    label: 'Absence Rate',
    plain: '% of school sessions missed due to any reason',
    detail: 'Lower is better. The national average is around 5%.',
  },
  persistent_absence_pct: {
    label: 'Persistent Absence',
    plain: '% of pupils missing 10% or more of school sessions',
    detail: 'Lower is better. Persistent absence can significantly affect attainment.',
  },
  rwm_expected_disadvantaged_pct: {
    label: 'Disadvantaged Pupils — Reading, Writing & Maths',
    plain: '% of disadvantaged pupils achieving the expected standard in all three subjects',
  },
  disadvantaged_gap: {
    label: 'Disadvantaged Gap',
    plain: 'Difference in attainment between disadvantaged pupils and their peers',
    detail: 'A smaller gap means the school is doing more to support disadvantaged pupils.',
  },
};

/**
 * Returns a plain-English band label for a KS2 progress score.
 * Progress scores are centred at 0 (= national average).
 */
export function progressBand(score: number): string {
  if (score > 3) return 'well above average';
  if (score > 1) return 'above average';
  if (score >= -1) return 'around average';
  if (score >= -3) return 'below average';
  return 'well below average';
}