/* The Lean 4 language for Monaco — registered once, client-side.
 *
 * A Monarch tokenizer (keywords, tactics, commands, the nested `/- -/`
 * comments Lean uses for docstrings) plus themes built from the wiki's live
 * palette, so the editor matches the page around it and follows the wiki's
 * theme *and* accent switches live: the accent — caret, selection, active
 * line number, keywords — is sampled from the `--accent` custom properties
 * that `[data-accent]` swaps. (Lean's own server also offers semantic
 * highlighting; keyword colours are the honest first pass — see the note in
 * lean/README.) */
import * as monaco from 'monaco-editor'

export const LEAN_LANGUAGE = 'lean4'
export const LEAN_THEMES = { light: 'mathew-light', dark: 'mathew-dark' } as const

/* words that introduce declarations, terms, and structuring */
const keywords = [
  'abstract', 'axiom', 'by', 'cases', 'catch', 'class', 'command', 'deriving', 'do',
  'else', 'end', 'example', 'expansion', 'explicit', 'export', 'def', 'theorem',
  'lemma', 'corollary', 'proposition', 'instance', 'structure', 'inductive', 'abbrev',
  'mutual', 'namespace', 'section', 'open', 'protected', 'private', 'partial',
  'noncomputable', 'set_option', 'unset_option', 'option', 'attribute', 'variable',
  'variables', 'include', 'hiding', 'renaming', 'as', 'where', 'from', 'show',
  'have', 'suffices', 'let', 'in', 'if', 'then', 'match', 'with', 'without', 'fun',
  'forall', 'at', 'using', 'via', 'override', 'obsolete', 'inherit', 'field',
  'generalizing', 'replacing', 'renaming', 'specializing', 'unshuffling', 'case',
  'dive', 'guard', 'modifies', 'macro', 'macro_rules', 'syntax', 'elab', 'elab_rules',
  'notation', 'infix', 'infixl', 'infixr', 'prefix', 'postfix', 'binders',
  'declare_syntax_cat', 'syntax_cat', 'extend', 'scoped', 'unused', 'auto_unfold',
  'extern', 'implemented_by', 'native_decide', 'lift', 'coe', 'coe_struct',
  'classical', 'decidable', 'universe', 'universes', 'exit',
]

/* tactics — the words after `by` and inside tactic blocks */
const tactics = [
  'intro', 'intros', 'exact', 'apply', 'refine', 'have', 'obtain', 'use', 'exists',
  'constructor', 'left', 'right', 'simp', 'simp_all', 'simp_rw', 'rw', 'rewrite',
  'show', 'conv', 'calc', 'ring', 'ring_nf', 'field_simp', 'norm_num', 'omega',
  'linarith', 'nlinarith', 'positivity', 'decide', 'trivial', 'rfl', 'refl', 'symm',
  'trans', 'ext', 'funext', 'congr', 'congr!', 'cases', 'induction', 'rcases',
  'obtain', 'subst', 'contradiction', 'exfalso', 'push_neg', 'contrapose',
  'constructor', 'aesop', 'tauto', 'bv_decide', 'gcongr', 'change', 'generalize',
  'revert', 'clear', 'rename_i', 'next', 'any_goals', 'all_goals', 'focus', 'dotl',
  'by_contra', 'by_contra!', 'apply_fun', 'congr_arg', 'congrFun', 'congrArg',
  'simpa', 'simpa using', 'norm_cast', 'exact?', 'apply?', 'sorry', 'native_decide',
  'unfold', 'dsimp', 'unfold_projs', 'whisker', 'thm_to_tactic', 'tauto', 'mt',
  'absurd', 'injection', 'no_index', 'guard_goals', 'expect_failure', 'stop', 'skip',
  'trace', 'log', 'sleep', 'wait', 'recover', 'error',
]

const commands = ['#check', '#eval', '#reduce', '#synth', '#print', '#exit', '#where', '#hole', '#why', '#loogle', '#guard']

let registered = false

export function registerLeanLanguage() {
  if (registered) return
  registered = true

  monaco.languages.register({ id: LEAN_LANGUAGE })

  monaco.languages.setLanguageConfiguration(LEAN_LANGUAGE, {
    comments: { lineComment: '--', blockComment: ['/-', '-/'] },
    brackets: [
      ['{', '}'], ['[', ']'], ['(', ')'],
      ['⟨', '⟩'], ['⟦', '⟧'], ['‹', '›'], ['⦃', '⦄'], ['⁅', '⁆'], ['⌈', '⌉'], ['⌊', '⌋'],
    ],
    autoClosingPairs: [
      { open: '{', close: '}' }, { open: '[', close: ']' }, { open: '(', close: ')' },
      { open: '"', close: '"' }, { open: '/-', close: '-/' },
      { open: '⟨', close: '⟩' }, { open: '⟦', close: '⟧' }, { open: '‹', close: '›' },
    ],
    surroundingPairs: [
      { open: '{', close: '}' }, { open: '[', close: ']' }, { open: '(', close: ')' },
      { open: '"', close: '"' }, { open: '⟨', close: '⟩' }, { open: '⟦', close: '⟧' },
      { open: '‹', close: '›' },
    ],
    indentationRules: {
      increaseIndentPattern: /^\s*(\bby\b|\bdo\b|\bthen\b|\bcalc\b|\{[^}]*$|\[[^\]]*$|\([^)]*$)/,
      decreaseIndentPattern: /^\s*(\bend\b|\}|\\|\)|\/-})/,
    },
  })

  monaco.languages.setMonarchTokensProvider(LEAN_LANGUAGE, {
    keywords,
    tactics,
    commands,
    tokenizer: {
      root: [
        [/--.*$/, 'comment'],
        [/\/-/, { token: 'comment', next: '@blockcomment' }],
        [/"/, { token: 'string', next: '@string' }],
        [/[0-9]+\.[0-9]+([eE][-+]?[0-9]+)?/, 'number.float'],
        [/[0-9]+([eE][-+]?[0-9]+)?[nNzQqR]?/, 'number'],
        [
          // one identifier run (ascii word, or a unicode run — Lean names
          // carry α, →, ≤, ⁻¹), then decided against the word lists
          /[a-zA-Z_#][a-zA-Z0-9_?!'∆∇]*|[^\x00-\x7F][a-zA-Z0-9_?!'∆∇]*/,
          {
            cases: {
              '@commands': 'keyword.command',
              '@tactics': 'keyword.tactic',
              '@keywords': 'keyword',
              '@default': 'identifier',
            },
          },
        ],
        [/^\s*@\[[^\]]*\]/, 'annotation'],
        [/[→←↔∧∨¬∀∃≠≤≥<>!=+\-*/^|&~:;.,@#][=]?/, 'operator'],
      ],
      blockcomment: [
        [/\/-/, { token: 'comment', next: '@blockcomment' }],
        [/-\//, { token: 'comment', next: '@pop' }],
        [/[^\-\/]+/, 'comment'],
        [/[\/-]/, 'comment'],
      ],
      string: [
        [/[^\\"]+/, 'string'],
        [/\\./, 'string.escape'],
        [/"/, { token: 'string', next: '@pop' }],
      ],
    },
  })
}

/* ---------- the wiki's palette, read live, as editor themes ---------- */

/* Monaco themes are plain hex, not CSS variables, so the accent is sampled
 * off the document each time a theme is built — the same read the canvas
 * surfaces make. The fallbacks are violet, the wiki's default accent. */
function wikiAccent(dark: boolean) {
  const css = getComputedStyle(document.documentElement)
  const at = (name: string, fallback: string) => css.getPropertyValue(name).trim() || fallback
  return {
    accent: at('--accent', dark ? '#7c8cff' : '#4f5fe8'),
    strong: at('--accent-strong', dark ? '#99a5ff' : '#3d4dd6'),
    second: at('--accent-2', dark ? '#38d3ee' : '#0ea5c9'),
  }
}

/* `#rrggbbaa` — Monaco's translucent form, standing in for the wiki's
 * `color-mix`. Shorthand hex is widened; anything else passes through. */
function alpha(hex: string, a: string) {
  if (/^#[0-9a-f]{3}$/i.test(hex)) return `#${hex.slice(1).split('').map(c => c + c).join('')}${a}`
  return /^#[0-9a-f]{6}$/i.test(hex) ? `${hex}${a}` : hex
}

/* token rules take hex without the leading `#` */
function ink(hex: string) {
  return hex.replace(/^#/, '')
}

/* Themes are named by their palette (mathew-dark-fb7185…): a new accent
 * yields a fresh theme rather than one Monaco may have cached under an old
 * palette, and a reader cycling back reuses a definition already made. */
const definedThemes = new Set<string>()

/* the theme matching the wiki right now — [data-theme] picks the surfaces,
 * [data-accent] the caret, selection, active line number and keywords */
export function currentLeanTheme(): string {
  const dark = document.documentElement.getAttribute('data-theme') === 'dark'
  const a = wikiAccent(dark)
  const name = `${dark ? LEAN_THEMES.dark : LEAN_THEMES.light}-${ink(a.accent)}-${ink(a.strong)}-${ink(a.second)}`.toLowerCase()
  if (definedThemes.has(name)) return name
  definedThemes.add(name)

  monaco.editor.defineTheme(name, dark
    ? {
        base: 'vs-dark',
        inherit: true,
        rules: [
          { token: 'keyword', foreground: ink(a.strong) },
          { token: 'keyword.tactic', foreground: '38d3ee' },
          { token: 'keyword.command', foreground: ink(a.strong), fontStyle: 'bold' },
          { token: 'string', foreground: '3fce8b' },
          { token: 'number', foreground: 'f5a83c' },
          { token: 'comment', foreground: '6b7488', fontStyle: 'italic' },
          { token: 'annotation', foreground: '99a1b5' },
          { token: 'operator', foreground: '99a1b5' },
          { token: 'type.identifier', foreground: '38d3ee' },
        ],
        colors: {
          'editor.background': '#141826',
          'editor.foreground': '#e7eaf3',
          'editor.lineHighlightBackground': '#1a2030',
          'editorLineNumber.foreground': '#6b7488',
          'editorLineNumber.activeForeground': a.accent,
          'editorCursor.foreground': a.accent,
          'editor.selectionBackground': alpha(a.accent, '40'),
          'editor.selectionHighlightBackground': alpha(a.accent, '1f'),
          'editorIndentGuide.background1': '#232a3c',
          'editorIndentGuide.activeBackground1': '#313a52',
          'editorWhitespace.foreground': '#313a52',
          'editorWidget.background': '#10131c',
          'editorWidget.border': '#232a3c',
          'editorSuggestWidget.selectedBackground': '#1a2030',
          'editorHoverWidget.background': '#10131c',
          'editorHoverWidget.border': '#232a3c',
          'scrollbarSlider.background': '#e7eaf329',
          'scrollbarSlider.hoverBackground': '#e7eaf347',
          'scrollbarSlider.activeBackground': '#e7eaf366',
          'editorError.foreground': '#f47085',
          'editorWarning.foreground': '#f5a83c',
          'editorInfo.foreground': a.second,
        },
      }
    : {
        base: 'vs',
        inherit: true,
        rules: [
          { token: 'keyword', foreground: ink(a.strong) },
          { token: 'keyword.tactic', foreground: '0891b2' },
          { token: 'keyword.command', foreground: ink(a.strong), fontStyle: 'bold' },
          { token: 'string', foreground: '189a5c' },
          { token: 'number', foreground: 'd97706' },
          { token: 'comment', foreground: '8a93a8', fontStyle: 'italic' },
          { token: 'annotation', foreground: '5b6478' },
          { token: 'operator', foreground: '5b6478' },
          { token: 'type.identifier', foreground: '0891b2' },
        ],
        colors: {
          'editor.background': '#ffffff',
          'editor.foreground': '#1b2130',
          'editor.lineHighlightBackground': '#eef1f7',
          'editorLineNumber.foreground': '#8a93a8',
          'editorLineNumber.activeForeground': a.accent,
          'editorCursor.foreground': a.accent,
          'editor.selectionBackground': alpha(a.accent, '33'),
          'editor.selectionHighlightBackground': alpha(a.accent, '1a'),
          'editorIndentGuide.background1': '#e2e6ef',
          'editorIndentGuide.activeBackground1': '#cfd5e3',
          'editorWhitespace.foreground': '#cfd5e3',
          'editorWidget.background': '#ffffff',
          'editorWidget.border': '#e2e6ef',
          'editorSuggestWidget.selectedBackground': '#eef1f7',
          'editorHoverWidget.background': '#ffffff',
          'editorHoverWidget.border': '#e2e6ef',
          'scrollbarSlider.background': '#1b213024',
          'scrollbarSlider.hoverBackground': '#1b21304d',
          'scrollbarSlider.activeBackground': '#1b213066',
          'editorError.foreground': '#d1344b',
          'editorWarning.foreground': '#d97706',
          'editorInfo.foreground': a.second,
        },
      })

  return name
}

/* move the editor to the palette the wiki is wearing right now */
export function applyLeanTheme() {
  monaco.editor.setTheme(currentLeanTheme())
}