'use strict';

const crypto = require('crypto');
const fs = require('fs');
const path = require('path');

const MAX_LABEL = 120;
const ID_RE = /^[A-Za-z0-9._:-]{1,120}$/;

function cleanLabel(value, fallback = '') {
  const text = String(value == null ? '' : value).trim().replace(/[\r\n\t]+/g, ' ');
  return text.slice(0, MAX_LABEL) || fallback;
}

function newId(prefix = '') {
  const id = crypto.randomUUID();
  return prefix ? `${cleanLabel(prefix).replace(/[^A-Za-z0-9_-]/g, '')}_${id}` : id;
}

function validId(value) {
  return ID_RE.test(String(value || '').trim());
}

function createUsageContext(input = {}) {
  const usageTraceId = validId(input.usageTraceId) ? String(input.usageTraceId).trim() : newId('usage');
  const reportId = input.reportId == null || input.reportId === ''
    ? null
    : (validId(input.reportId) ? String(input.reportId).trim() : newId('report'));
  return {
    usageTraceId,
    reportId,
    skillId: cleanLabel(input.skillId, 'voc-api-catalog'),
    workflowType: cleanLabel(input.workflowType, 'voc_custom_workflow'),
    title: cleanLabel(input.title || input.task),
    clientId: cleanLabel(input.clientId),
    stepId: cleanLabel(input.stepId),
    budgetLimitCny: Number.isFinite(Number(input.budgetLimitCny ?? input.budgetCny))
      ? Math.max(0, Number(input.budgetLimitCny ?? input.budgetCny))
      : null,
    pricingVersion: cleanLabel(input.pricingVersion),
    createdAt: input.createdAt || new Date().toISOString()
  };
}

function createStepContext(context, stepId, extra = {}) {
  const base = createUsageContext({ ...context, stepId });
  return {
    ...base,
    requestId: validId(extra.requestId) ? String(extra.requestId).trim() : newId('request'),
    ...(extra.entityId ? { entityId: cleanLabel(extra.entityId) } : {}),
    ...(extra.batchIndex !== undefined ? { batchIndex: Number(extra.batchIndex) || 0 } : {})
  };
}

function usageHeaders(context = {}) {
  const headers = {};
  const values = {
    'X-Fmode-Usage-Trace-Id': context.usageTraceId,
    'X-Fmode-Report-Id': context.reportId,
    'X-Fmode-Skill-Id': context.skillId,
    'X-Fmode-Workflow-Type': context.workflowType,
    'X-Fmode-Step-Id': context.stepId,
    'X-Fmode-Client-Id': context.clientId,
    'X-Fmode-Request-Id': context.requestId
  };
  for (const [name, value] of Object.entries(values)) {
    if (value && validId(value)) headers[name] = String(value);
  }
  return headers;
}

function contextForTool(input = {}) {
  return createUsageContext({
    ...input,
    budgetLimitCny: input.budgetLimitCny ?? input.budgetCny
  });
}

function writeUsageContext(context, outputDir) {
  if (!outputDir) return null;
  const dir = path.resolve(String(outputDir));
  fs.mkdirSync(dir, { recursive: true });
  const filePath = path.join(dir, 'usage-context.json');
  fs.writeFileSync(filePath, JSON.stringify(context, null, 2));
  return filePath;
}

module.exports = {
  MAX_LABEL,
  cleanLabel,
  newId,
  validId,
  createUsageContext,
  createStepContext,
  contextForTool,
  usageHeaders,
  writeUsageContext
};