src/lib/export-service.ts

import { authFetch } from "@/lib/api";
import { FilterFormValues } from "@/types/candidate-table";

/**
 * Fetch all candidates without pagination for export
 */
export const fetchAllCandidatesForExport = async (
  search: string,
  sortConfig: { key: string | null; direction: "asc" | "desc" },
  filters: FilterFormValues,
  criteriaId: string | null
): Promise<any[]> => {
  const params = new URLSearchParams()

  // Set very high limit to get all results in one request
  // Adjust based on your backend's maximum limit
  params.set("page", "1")
  params.set("limit", "10000") // Fetch up to 10,000 records

  if (search) params.set("search", search)
  if (sortConfig.key) {
    params.set("sortBy", sortConfig.key)
    params.set("sortOrder", sortConfig.direction)
  }

  if (filters.domicile) params.set("domicile", filters.domicile)
  if (filters.yoe) params.set("yoe", filters.yoe)
  filters.educations.forEach((edu, i) => {
    const n = i + 1
    if (edu.university) params.set(`univ_edu_${n}`, edu.university)
    if (edu.major) params.set(`major_edu_${n}`, edu.major)
    if (edu.gpa) params.set(`gpa_${n}`, edu.gpa)
  })
  if (filters.softskills) params.append("softskills", filters.softskills)
  if (filters.hardskills) params.append("hardskills", filters.hardskills)
  if (filters.certifications) params.append("certifications", filters.certifications)
  if (filters.businessDomain) params.append("business_domain", filters.businessDomain)
  if (criteriaId) params.append("criteria_id", criteriaId)

  const res = await authFetch(`/api/cv-profile?${params}`)
  if (!res.ok) throw new Error("Failed to fetch candidates for export")
  
  const data = await res.json()
  return data.data ?? []
}

/**
 * Convert candidates array to CSV string
 */
export const generateCSVContent = (candidates: any[]): string => {
  if (candidates.length === 0) return ""

  // Define all possible columns
  const columns = [
    "profile_id",
    "fullname",
    "domicile",
    "yoe",
    "univ_edu_1",
    "major_edu_1",
    "gpa_edu_1",
    "univ_edu_2",
    "major_edu_2",
    "gpa_edu_2",
    "univ_edu_3",
    "major_edu_3",
    "gpa_edu_3",
    "hardskills",
    "softskills",
    "certifications",
    "business_domain",
    "score",
  ]

  // CSV Header
  const header = columns.join(",")

  // CSV Rows
  const rows = candidates.map((candidate) =>
    columns
      .map((col) => {
        const value = candidate[col]

        // Handle arrays (join with semicolon)
        if (Array.isArray(value)) {
          return `"${value.join("; ")}"`
        }

        // Handle null/undefined
        if (value === null || value === undefined) {
          return ""
        }

        // Handle strings with commas or quotes (escape them)
        const stringValue = String(value)
        if (stringValue.includes(",") || stringValue.includes('"') || stringValue.includes("\n")) {
          return `"${stringValue.replace(/"/g, '""')}"` // Escape quotes
        }

        return stringValue
      })
      .join(",")
  )

  return [header, ...rows].join("\n")
}

/**
 * Trigger CSV download in browser
 */
export const downloadCSV = (content: string, filename: string = "candidates.csv"): void => {
  const blob = new Blob([content], { type: "text/csv;charset=utf-8;" })
  const link = document.createElement("a")
  const url = URL.createObjectURL(blob)

  link.setAttribute("href", url)
  link.setAttribute("download", filename)
  link.style.visibility = "hidden"

  document.body.appendChild(link)
  link.click()
  document.body.removeChild(link)

  URL.revokeObjectURL(url)
}

/**
 * Main export function - orchestrates fetch, generate, and download
 */
export const exportCandidatesToCSV = async (
  search: string,
  sortConfig: { key: string | null; direction: "asc" | "desc" },
  filters: FilterFormValues,
  criteriaId: string | null,
  userId: string
): Promise<void> => {
  try {
    const params = new URLSearchParams()

    if (search) params.set("search", search)
    if (sortConfig.key) {
      params.set("sortBy", sortConfig.key)
      params.set("sortOrder", sortConfig.direction)
    }

    if (filters.domicile) params.set("domicile", filters.domicile)
  if (filters.yoe) params.set("yoe", filters.yoe)
  filters.educations.forEach((edu, i) => {
    const n = i + 1
    // Handle arrays for university and major
    edu.university.forEach((univ) => params.append(`univ_edu_${n}`, univ))
    edu.major.forEach((maj) => params.append(`major_edu_${n}`, maj))
    if (edu.gpa) params.set(`gpa_${n}`, edu.gpa)
  })
  // Updated to handle arrays
  filters.softskills.forEach((skill) => params.append("softskills", skill))
  filters.hardskills.forEach((skill) => params.append("hardskills", skill))
  filters.certifications.forEach((cert) => params.append("certifications", cert))
  filters.businessDomain.forEach((domain) => params.append("business_domain", domain))
  
  if (criteriaId) params.append("criteria_id", criteriaId)
  params.append("user_id", userId)

    // Call backend export endpoint
    const response = await authFetch(`/api/cv-profile/export?${params}`, {
      method: "GET",
      headers: {
        "Accept": "text/csv",
      },
    })

    if (!response.ok) {
      const error = await response.json()
      throw new Error(error.error || "Export failed")
    }

    // Get blob and trigger download
    const blob = await response.blob()
    const url = window.URL.createObjectURL(blob)
    const link = document.createElement("a")
    link.href = url
    
    // Extract filename from Content-Disposition header
    const contentDisposition = response.headers.get("Content-Disposition")
    const filename = contentDisposition
      ? contentDisposition.split("filename=")[1]?.replace(/"/g, "")
      : `candidates-${new Date().toISOString().slice(0, 10)}.csv`
    
    link.setAttribute("download", filename)
    document.body.appendChild(link)
    link.click()
    
    // Cleanup
    document.body.removeChild(link)
    window.URL.revokeObjectURL(url)

  } catch (error) {
    console.error("Export failed:", error)
    throw error
  }
}