/**
* Natural language time range parser
* Converts expressions like "last week", "yesterday" to date ranges
*/
export interface TimeRange {
startDate: string; // YYYY-MM-DD
endDate: string; // YYYY-MM-DD
}
/**
* Parse a natural language time expression to a date range
* Returns null if the expression is not recognized
*/
export function parseTimeRange(expression: string): TimeRange | null {
const now = new Date();
const today = startOfDay(now);
const expr = expression.toLowerCase().trim();
// Yesterday
if (expr === 'yesterday') {
const yesterday = addDays(today, -1);
return {
startDate: formatDate(yesterday),
endDate: formatDate(yesterday),
};
}
// Today
if (expr === 'today') {
return {
startDate: formatDate(today),
endDate: formatDate(today),
};
}
// This week (Monday to today)
if (expr === 'this week') {
const startOfWeek = getStartOfWeek(today);
return {
startDate: formatDate(startOfWeek),
endDate: formatDate(today),
};
}
// Last week (previous Monday to Sunday)
if (expr === 'last week') {
const thisWeekStart = getStartOfWeek(today);
const lastWeekStart = addDays(thisWeekStart, -7);
const lastWeekEnd = addDays(thisWeekStart, -1);
return {
startDate: formatDate(lastWeekStart),
endDate: formatDate(lastWeekEnd),
};
}
// This month (1st to today)
if (expr === 'this month') {
const startOfMonth = new Date(today.getFullYear(), today.getMonth(), 1);
return {
startDate: formatDate(startOfMonth),
endDate: formatDate(today),
};
}
// Last month
if (expr === 'last month') {
const lastMonthStart = new Date(today.getFullYear(), today.getMonth() - 1, 1);
const lastMonthEnd = new Date(today.getFullYear(), today.getMonth(), 0);
return {
startDate: formatDate(lastMonthStart),
endDate: formatDate(lastMonthEnd),
};
}
// "last N days" / "past N days"
const lastDaysMatch = expr.match(/^(?:last|past)\s+(\d+)\s*days?$/);
if (lastDaysMatch) {
const days = parseInt(lastDaysMatch[1], 10);
const startDate = addDays(today, -days);
return {
startDate: formatDate(startDate),
endDate: formatDate(today),
};
}
// "last N weeks" / "past N weeks"
const lastWeeksMatch = expr.match(/^(?:last|past)\s+(\d+)\s*weeks?$/);
if (lastWeeksMatch) {
const weeks = parseInt(lastWeeksMatch[1], 10);
const startDate = addDays(today, -weeks * 7);
return {
startDate: formatDate(startDate),
endDate: formatDate(today),
};
}
// "last N months" / "past N months"
const lastMonthsMatch = expr.match(/^(?:last|past)\s+(\d+)\s*months?$/);
if (lastMonthsMatch) {
const months = parseInt(lastMonthsMatch[1], 10);
const startDate = new Date(today.getFullYear(), today.getMonth() - months, today.getDate());
return {
startDate: formatDate(startDate),
endDate: formatDate(today),
};
}
// Not recognized
return null;
}
/**
* Check if a string looks like a natural time expression
*/
export function isTimeExpression(str: string): boolean {
const expr = str.toLowerCase().trim();
const patterns = [
/^yesterday$/,
/^today$/,
/^this\s+(?:week|month)$/,
/^last\s+(?:week|month)$/,
/^(?:last|past)\s+\d+\s*(?:days?|weeks?|months?)$/,
];
return patterns.some(pattern => pattern.test(expr));
}
// Helper functions
function startOfDay(date: Date): Date {
const result = new Date(date);
result.setHours(0, 0, 0, 0);
return result;
}
function addDays(date: Date, days: number): Date {
const result = new Date(date);
result.setDate(result.getDate() + days);
return result;
}
function getStartOfWeek(date: Date): Date {
const result = new Date(date);
const day = result.getDay();
// Adjust to Monday (day 1), if Sunday (day 0), go back 6 days
const diff = day === 0 ? 6 : day - 1;
result.setDate(result.getDate() - diff);
return result;
}
function formatDate(date: Date): string {
const year = date.getFullYear();
const month = String(date.getMonth() + 1).padStart(2, '0');
const day = String(date.getDate()).padStart(2, '0');
return `${year}-${month}-${day}`;
}
