All files / web/src/components/flowchart MathDisplay.tsx

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
'use client'

import { css } from '../../../styled-system/css'

interface MathDisplayProps {
  /** Math expression string to render (e.g., "3 2/9 − 1 1/2" or "2x = 12") */
  expression: string
  /** Font size for the display */
  size?: 'sm' | 'md' | 'lg' | 'xl'
}

/**
 * Math font stack optimized for MathML rendering.
 * STIX Two Math is the gold standard for web math typography.
 * Fallbacks include system math fonts and common alternatives.
 */
const mathFontFamily = [
  '"STIX Two Math"',
  '"Cambria Math"',
  '"Latin Modern Math"',
  '"XITS Math"',
  'math',
  'serif',
].join(', ')

/**
 * Renders math expressions using native MathML.
 * Parses strings like "3 2/9 − 1 1/2" and renders proper semantic math.
 *
 * Browser support: 94%+ (Chrome 109+, Firefox, Safari 10+, Edge 109+)
 */
export function MathDisplay({ expression, size = 'lg' }: MathDisplayProps) {
  const fontSize = {
    sm: '1.25rem',
    md: '1.5rem',
    lg: '1.75rem',
    xl: '2.25rem',
  }[size]

  // Parse the expression into tokens
  const tokens = parseExpression(expression)

  return (
    <math
      data-testid="math-display"
      data-expression={expression}
      data-size={size}
      data-token-count={tokens.length}
      className={css({
        display: 'inline-flex',
        alignItems: 'center',
        verticalAlign: 'middle',
      })}
      style={{ fontSize, fontFamily: mathFontFamily }}
    >
      <mrow>{tokens.map((token, idx) => renderToken(token, idx))}</mrow>
    </math>
  )
}

type Token =
  | { type: 'number'; value: string }
  | { type: 'fraction'; numerator: string; denominator: string }
  | { type: 'mixed'; whole: string; numerator: string; denominator: string }
  | { type: 'operator'; value: string }
  | { type: 'variable'; name: string }
  | { type: 'term'; coefficient: string; variable: string }
  | { type: 'text'; value: string }

function parseExpression(expr: string): Token[] {
  const tokens: Token[] = []
  // Split by spaces but keep operators together
  const parts = expr.split(/\s+/)

  for (let i = 0; i < parts.length; i++) {
    const part = parts[i]

    // Check if it's an operator
    if (['−', '-', '+', '×', '÷', '=', '→'].includes(part)) {
      tokens.push({ type: 'operator', value: part })
      continue
    }

    // Check if it's a fraction (contains /)
    if (part.includes('/')) {
      const [num, denom] = part.split('/')
      // Check if previous token was a plain number (making this a mixed number)
      const prev = tokens[tokens.length - 1]
      if (prev && prev.type === 'number') {
        // Convert previous number + this fraction to mixed number
        tokens.pop()
        tokens.push({
          type: 'mixed',
          whole: prev.value,
          numerator: num,
          denominator: denom,
        })
      } else {
        tokens.push({ type: 'fraction', numerator: num, denominator: denom })
      }
      continue
    }

    // Check if it's a plain number
    if (/^-?\d+$/.test(part)) {
      tokens.push({ type: 'number', value: part })
      continue
    }

    // Check if it's a term like "2x" or "3y" (coefficient + variable)
    const termMatch = part.match(/^(-?\d*)([a-zA-Z])$/)
    if (termMatch) {
      const [, coef, varName] = termMatch
      if (coef === '' || coef === '-' || coef === '1' || coef === '-1') {
        // Coefficient of 1 is implicit: "1x" → "x", "-1x" → "-x"
        const isNegative = coef === '-' || coef === '-1'
        tokens.push({ type: 'variable', name: isNegative ? `-${varName}` : varName })
      } else {
        tokens.push({ type: 'term', coefficient: coef, variable: varName })
      }
      continue
    }

    // Check if it's a single variable
    if (/^[a-zA-Z]$/.test(part)) {
      tokens.push({ type: 'variable', name: part })
      continue
    }

    // Otherwise it's text
    tokens.push({ type: 'text', value: part })
  }

  return tokens
}

function renderToken(token: Token, key: number): React.ReactNode {
  switch (token.type) {
    case 'number':
      return <mn key={key}>{token.value}</mn>

    case 'fraction':
      return (
        <mfrac key={key}>
          <mn>{token.numerator}</mn>
          <mn>{token.denominator}</mn>
        </mfrac>
      )

    case 'mixed':
      return (
        <mrow key={key}>
          <mn>{token.whole}</mn>
          <mfrac>
            <mn>{token.numerator}</mn>
            <mn>{token.denominator}</mn>
          </mfrac>
        </mrow>
      )

    case 'operator':
      return <mo key={key}>{token.value}</mo>

    case 'variable':
      return <mi key={key}>{token.name}</mi>

    case 'term':
      return (
        <mrow key={key}>
          <mn>{token.coefficient}</mn>
          <mi>{token.variable}</mi>
        </mrow>
      )

    case 'text':
      return <mtext key={key}>{token.value}</mtext>
  }
}