/**
 * 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.',
  },
  sen_support_pct: {
    label: 'SEN Support',
    plain: '% of pupils receiving SEN (Special Educational Needs) support without a formal plan',
    detail: 'These pupils need extra help but do not yet have an Education, Health and Care Plan (EHCP).',
  },
  sen_ehcp_pct: {
    label: 'Education, Health and Care Plan (EHCP)',
    plain: '% of pupils with a formal EHCP — a legal plan for pupils with significant additional needs',
  },
  eal_pct: {
    label: 'English as an Additional Language',
    plain: '% of pupils whose first language is not English',
  },
  idaci_decile: {
    label: 'Deprivation (IDACI)',
    plain: 'How deprived the area around the school is. Decile 1 = most deprived 10% of areas in England.',
    detail: 'IDACI stands for Income Deprivation Affecting Children Index. It measures the proportion of children living in low-income households in an area.',
  },
  // ── KS4 / GCSE metrics ────────────────────────────────────────────────
  attainment_8_score: {
    label: 'Attainment 8',
    plain: 'Average grade across a pupil\'s best 8 GCSEs, including English and Maths',
    detail: 'Each GCSE grade is converted to a points score (grade 9 = 9 points, grade 1 = 1 point). The national average is around 46.',
  },
  progress_8_score: {
    label: 'Progress 8',
    plain: 'How much pupils improved from their primary school results to GCSE, compared to similar pupils nationally',
    detail: '0 = national average. Positive means better-than-expected progress; negative means lower-than-expected. A score above +0.5 is considered well above average.',
  },
  english_maths_standard_pass_pct: {
    label: 'English & Maths — Grade 4+ (Standard Pass)',
    plain: '% of pupils achieving at least a grade 4 in both English and Maths',
    detail: 'Grade 4 is the minimum "standard pass". Employers and colleges often require grade 4 in English and Maths.',
  },
  english_maths_strong_pass_pct: {
    label: 'English & Maths — Grade 5+ (Strong Pass)',
    plain: '% of pupils achieving at least a grade 5 in both English and Maths',
    detail: 'Grade 5 is a "strong pass". Many sixth forms and universities expect grade 5 in English and Maths.',
  },
  ebacc_entry_pct: {
    label: 'EBacc Entry',
    plain: '% of pupils who entered the English Baccalaureate — a set of GCSE subjects covering English, Maths, Sciences, a Language, and Humanities',
    detail: 'EBacc entry keeps academic options open post-16. It is not a separate qualification.',
  },
  ebacc_standard_pass_pct: {
    label: 'EBacc — Grade 4+ (Standard Pass)',
    plain: '% of pupils achieving grade 4 or above across all EBacc subjects',
  },
  ebacc_strong_pass_pct: {
    label: 'EBacc — Grade 5+ (Strong Pass)',
    plain: '% of pupils achieving grade 5 or above across all EBacc subjects',
  },
  ebacc_avg_score: {
    label: 'EBacc Average Score',
    plain: 'Average points score across all EBacc subject entries',
  },
  gcse_grade_91_pct: {
    label: 'GCSE Grade 9–1 %',
    plain: '% of GCSE entries where a pupil achieved a grade between 9 (highest) and 1',
  },
};

/**
 * 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';
}