@atomic-ehr/ucum/dist/parser/lexer.js

TypeScript implementation of UCUM (Unified Code for Units of Measure)

export class Lexer {
    input;
    position = 0;
    tokens = [];
    constructor(input) {
        this.input = input;
    }
    tokenize() {
        while (this.position < this.input.length) {
            this.skipWhitespace();
            if (this.position >= this.input.length)
                break;
            const char = this.input[this.position];
            if (char === '.') {
                this.addToken('DOT', char);
            }
            else if (char === '/') {
                this.addToken('SLASH', char);
            }
            else if (char === '(') {
                this.addToken('LPAREN', char);
            }
            else if (char === ')') {
                this.addToken('RPAREN', char);
            }
            else if (char === '{') {
                this.addToken('LBRACE', char);
            }
            else if (char === '}') {
                this.addToken('RBRACE', char);
            }
            else if (char === '^') {
                this.addToken('CARET', char);
            }
            else if (char === '+') {
                this.addToken('PLUS', char);
            }
            else if (char === '-') {
                this.addToken('MINUS', char);
            }
            else if (char === '*') {
                this.addToken('STAR', char);
            }
            else if (char && this.isDigit(char)) {
                this.readNumber();
            }
            else if (char && (this.isLetter(char) || char === '[' || char === '%' || char === "'")) {
                this.readAtomOrPrefix();
            }
            else {
                throw new Error(`Unexpected character '${char}' at position ${this.position}`);
            }
        }
        this.tokens.push({ type: 'EOF', value: '', position: this.position, length: 0 });
        return this.tokens;
    }
    skipWhitespace() {
        while (this.position < this.input.length) {
            const char = this.input[this.position];
            if (!char || !/\s/.test(char))
                break;
            this.position++;
        }
    }
    isDigit(char) {
        if (!char)
            return false;
        return /[0-9]/.test(char);
    }
    isLetter(char) {
        if (!char)
            return false;
        return /[a-zA-Z]/.test(char);
    }
    readNumber() {
        const start = this.position;
        while (this.position < this.input.length && this.input[this.position] && this.isDigit(this.input[this.position])) {
            this.position++;
        }
        const value = this.input.slice(start, this.position);
        this.tokens.push({ type: 'DIGIT', value, position: start, length: value.length });
    }
    readAtomOrPrefix() {
        const start = this.position;
        let value = '';
        const char = this.input[this.position];
        if (!char)
            return;
        // Handle special cases like [, %, '
        if (char === '[') {
            // Read until matching ]
            value += this.input[this.position++];
            while (this.position < this.input.length && this.input[this.position] !== ']') {
                value += this.input[this.position++];
            }
            if (this.position < this.input.length && this.input[this.position] === ']') {
                value += this.input[this.position++];
            }
        }
        else if (char === '%') {
            value = char;
            this.position++;
            // Check if % is followed by a bracketed annotation like %[slope]
            if (this.position < this.input.length && this.input[this.position] === '[') {
                value += this.input[this.position++];
                while (this.position < this.input.length && this.input[this.position] !== ']') {
                    value += this.input[this.position++];
                }
                if (this.position < this.input.length && this.input[this.position] === ']') {
                    value += this.input[this.position++];
                }
            }
        }
        else if (char === "'") {
            value = char;
            this.position++;
        }
        else {
            // Read letters
            while (this.position < this.input.length && this.input[this.position] && (this.isLetter(this.input[this.position]) || this.input[this.position] === '_')) {
                value += this.input[this.position++];
            }
            // Check if this is followed by a bracketed annotation like B[W] or B[SPL]
            if (this.position < this.input.length && this.input[this.position] === '[') {
                // This is part of the same atom
                value += this.input[this.position++];
                while (this.position < this.input.length && this.input[this.position] !== ']') {
                    value += this.input[this.position++];
                }
                if (this.position < this.input.length && this.input[this.position] === ']') {
                    value += this.input[this.position++];
                }
            }
        }
        // For now, mark everything as ATOM - the parser will disambiguate
        this.tokens.push({ type: 'ATOM', value, position: start, length: value.length });
    }
    addToken(type, value) {
        this.tokens.push({ type, value, position: this.position, length: value.length });
        this.position++;
    }
}