// Context size limit and trimming logic.

/**
 * Validates and trims input to stay within character budget.
 *
 * @param {{ question: string, context?: string, projectSummary?: string, taskSummary?: string, relevantFiles?: Array<{ path: string, content: string }>, logs?: string }} input
 * @param {{ maxInputChars: number, maxFileChars: number, maxFiles: number, maxLogChars: number }} config
 * @returns {{ ok: true, input: object, warnings: string[] } | { ok: false, error: string, warnings: string[], input: null }}
 */
export function checkContextBudget(input, config) {
  if (!input || typeof input.question !== 'string' || input.question.length === 0) {
    throw new Error('Validation error: question is required.');
  }

  const warnings = [];
  const files = input.relevantFiles ? [...input.relevantFiles] : [];
  let logs = input.logs ?? '';
  let context = input.context ?? '';
  let projectSummary = input.projectSummary ?? '';
  let taskSummary = input.taskSummary ?? '';

  // Step 1 — Enforce hard limits (maxFiles, maxFileChars, maxLogChars)
  if (files.length > config.maxFiles) {
    warnings.push(`Only the first ${config.maxFiles} relevant files were kept. (maxFiles=${config.maxFiles})`);
    files.splice(config.maxFiles);
  }

  for (const file of files) {
    if (file.content && file.content.length > config.maxFileChars) {
      warnings.push(`File ${file.path || 'unknown'} was truncated to ${config.maxFileChars} characters. (maxFileChars=${config.maxFileChars})`);
      file.content = file.content.slice(0, config.maxFileChars);
    }
  }

  if (logs.length > config.maxLogChars) {
    warnings.push(`Logs were truncated to ${config.maxLogChars} characters. (maxLogChars=${config.maxLogChars})`);
    logs = logs.slice(0, config.maxLogChars);
  }

  // Helper: count all input characters
  function countInputChars() {
    let total = input.question.length;
    if (context) total += context.length;
    if (projectSummary) total += projectSummary.length;
    if (taskSummary) total += taskSummary.length;
    if (logs) total += logs.length;
    for (const file of files) {
      total += file.content ? file.content.length : 0;
    }
    return total;
  }

  // Step 2 — If still over global limit, trim droppable sections
  let remaining = countInputChars();

  if (remaining > config.maxInputChars && context) {
    const allowed = Math.max(0, config.maxInputChars - remaining + context.length);
    if (allowed < context.length) {
      context = context.slice(0, allowed);
      warnings.push(`Context was trimmed to ${allowed} characters. (budget exceeded)`);
      remaining = countInputChars();
    }
  }

  if (remaining > config.maxInputChars && projectSummary) {
    const allowed = Math.max(0, config.maxInputChars - remaining + projectSummary.length);
    if (allowed < projectSummary.length) {
      projectSummary = projectSummary.slice(0, allowed);
      warnings.push(`Project summary was trimmed to ${allowed} characters. (budget exceeded)`);
      remaining = countInputChars();
    }
  }

  if (remaining > config.maxInputChars && taskSummary) {
    const allowed = Math.max(0, config.maxInputChars - remaining + taskSummary.length);
    if (allowed < taskSummary.length) {
      taskSummary = taskSummary.slice(0, allowed);
      warnings.push(`Task summary was trimmed to ${allowed} characters. (budget exceeded)`);
      remaining = countInputChars();
    }
  }

  // Step 3 — Final check: if question alone or question + hard-limited files/logs exceeds limit, reject
  remaining = countInputChars();

  if (remaining > config.maxInputChars) {
    return {
      ok: false,
      error:
        'Input is too large for a focused review. Please retry with only the specific files, diff, or error section relevant to the question.',
      warnings,
      input: null,
    };
  }

  // Build trimmed input object (only include non-empty optional fields)
  const trimmedInput = { question: input.question };
  if (context.length > 0) trimmedInput.context = context;
  if (projectSummary.length > 0) trimmedInput.projectSummary = projectSummary;
  if (taskSummary.length > 0) trimmedInput.taskSummary = taskSummary;
  if (files.length > 0) trimmedInput.relevantFiles = files;
  if (logs.length > 0) trimmedInput.logs = logs;

  return { ok: true, input: trimmedInput, warnings };
}