/**
* Utility for processing line range queries on log output
*/
import { RangeOptions, LogResourceError, LogErrorType } from '../types/logging.js';
/**
* Processes line range queries with support for negative indices
*/
export class LineRangeProcessor {
/**
* Process a range query on output
*
* @param output - The full output string
* @param start - Start line number (1-based, negative supported)
* @param end - End line number (1-based, negative supported)
* @param options - Range options
* @returns Formatted range output
*/
static processRange(
output: string,
start: number,
end: number,
options: RangeOptions
): string {
const lines = output.split('\n');
const totalLines = lines.length;
// Convert negative indices to positive
// -1 means last line, -2 means second to last, etc.
const actualStart = start < 0 ? totalLines + start + 1 : start;
const actualEnd = end < 0 ? totalLines + end + 1 : end;
// Validate range
this.validateRange(actualStart, actualEnd, totalLines);
// Extract lines (convert to 0-based for array indexing)
const selectedLines = lines.slice(actualStart - 1, actualEnd);
// Check maxLines limit if specified
if (options.maxLines && selectedLines.length > options.maxLines) {
throw new LogResourceError(
LogErrorType.INVALID_RANGE,
`Range exceeds maximum line limit of ${options.maxLines}`,
{ requestedLines: selectedLines.length, maxLines: options.maxLines }
);
}
// Format output
return this.formatLines(
selectedLines,
actualStart,
actualEnd,
totalLines,
options
);
}
/**
* Validate that the range is valid
*/
private static validateRange(
start: number,
end: number,
totalLines: number
): void {
if (start < 1) {
throw new LogResourceError(
LogErrorType.INVALID_RANGE,
`Start line must be >= 1, got ${start}`,
{ start, totalLines }
);
}
if (end > totalLines) {
throw new LogResourceError(
LogErrorType.INVALID_RANGE,
`End line ${end} exceeds total lines ${totalLines}`,
{ end, totalLines }
);
}
if (start > end) {
throw new LogResourceError(
LogErrorType.INVALID_RANGE,
`Start line ${start} must be <= end line ${end}`,
{ start, end }
);
}
}
/**
* Format lines with optional line numbers and header
*/
private static formatLines(
lines: string[],
startLineNumber: number,
endLineNumber: number,
totalLines: number,
options: RangeOptions
): string {
const parts: string[] = [];
// Header
parts.push(`Lines ${startLineNumber}-${endLineNumber} of ${totalLines}:`);
parts.push('');
// Format lines
if (options.lineNumbers) {
lines.forEach((line, index) => {
const lineNum = startLineNumber + index;
parts.push(`${lineNum}: ${line}`);
});
} else {
parts.push(...lines);
}
return parts.join('\n');
}
/**
* Calculate the actual range after resolving negative indices
*/
static resolveRange(
start: number,
end: number,
totalLines: number
): { actualStart: number; actualEnd: number } {
const actualStart = start < 0 ? totalLines + start + 1 : start;
const actualEnd = end < 0 ? totalLines + end + 1 : end;
return { actualStart, actualEnd };
}
}
