import type { IJMAPClient } from "@/lib/jmap/client-interface";
import { expandImportableEmails } from "@/lib/eml-import";

export type ConflictResolution = "skip" | "replace" | "copy";

export interface ImportProgress {
  total: number;
  processed: number;
  imported: number;
  skipped: number;
  failed: number;
  currentFile: string;
}

export interface ImportResult {
  imported: number;
  skipped: number;
  failed: number;
  errors: Array<{ file: string; error: string }>;
}

interface ParsedEml {
  messageId: string | null;
  subject: string;
  from: string;
  to: string;
  cc: string;
  date: string;
  bodyPlain: string;
  bodyHtml: string;
  raw: Blob;
}

async function parseEml(file: Blob): Promise<ParsedEml> {
  const { default: PostalMime } = await import("postal-mime");
  const buffer = await file.arrayBuffer();
  const parsed = await PostalMime.parse(buffer);

  return {
    messageId: (parsed.messageId || null) as string | null,
    subject: parsed.subject || "(No Subject)",
    from: typeof parsed.from === "object" && parsed.from?.address
      ? `${parsed.from.name || ""} <${parsed.from.address}>`.trim()
      : String(parsed.from || ""),
    to: Array.isArray(parsed.to)
      ? parsed.to.map((r: { address?: string; name?: string }) =>
          r.name ? `${r.name} <${r.address}>` : r.address || ""
        ).join(", ")
      : "",
    cc: Array.isArray(parsed.cc)
      ? parsed.cc.map((r: { address?: string; name?: string }) =>
          r.name ? `${r.name} <${r.address}>` : r.address || ""
        ).join(", ")
      : "",
    date: parsed.date || "",
    bodyPlain: parsed.text || "",
    bodyHtml: parsed.html || "",
    raw: file,
  };
}

async function findExistingMessageIds(
  client: IJMAPClient,
  messageIds: string[],
): Promise<Set<string>> {
  const existing = new Set<string>();
  const batchSize = 50;

  for (let i = 0; i < messageIds.length; i += batchSize) {
    const batch = messageIds.slice(i, i + batchSize);
    try {
      const conditions = batch.map((id) => ({
        header: ["Message-ID", `<${id}>`] as [string, string],
      }));

      const filter = conditions.length === 1
        ? conditions[0]
        : { operator: "OR", conditions };

      const { emails } = await client.advancedSearchEmails(filter, undefined, batchSize);
      for (const email of emails) {
        if (email.messageId && batch.includes(email.messageId)) {
          existing.add(email.messageId);
        }
      }
    } catch {
      // best-effort dedup lookup
    }
  }

  return existing;
}

function generateRfc822FromParsed(eml: ParsedEml): Blob {
  const lines: string[] = [];
  lines.push(`From: ${eml.from}`);
  if (eml.to) lines.push(`To: ${eml.to}`);
  if (eml.cc) lines.push(`Cc: ${eml.cc}`);
  if (eml.messageId) lines.push(`Message-ID: <${eml.messageId}>`);
  lines.push(`Date: ${eml.date || new Date().toUTCString()}`);
  lines.push(`Subject: ${eml.subject}`);
  lines.push("MIME-Version: 1.0");

  if (eml.bodyHtml) {
    const boundary = `----=_Boundary_${Date.now().toString(36)}`;
    lines.push(`Content-Type: multipart/alternative; boundary="${boundary}"`);
    lines.push("");
    lines.push(`--${boundary}`);
    lines.push("Content-Type: text/plain; charset=utf-8");
    lines.push("Content-Transfer-Encoding: quoted-printable");
    lines.push("");
    lines.push(eml.bodyPlain);
    lines.push(`--${boundary}`);
    lines.push("Content-Type: text/html; charset=utf-8");
    lines.push("Content-Transfer-Encoding: quoted-printable");
    lines.push("");
    lines.push(eml.bodyHtml);
    lines.push(`--${boundary}--`);
  } else {
    lines.push("Content-Type: text/plain; charset=utf-8");
    lines.push("Content-Transfer-Encoding: quoted-printable");
    lines.push("");
    lines.push(eml.bodyPlain);
  }

  return new Blob([lines.join("\r\n")], { type: "message/rfc822" });
}

async function extractMessageIdFromEml(blob: Blob): Promise<string | null> {
  try {
    const text = await blob.text();
    const match = text.match(/^Message-ID:\s*(.+)$/im);
    if (match) {
      return match[1].trim().replace(/^<+/, "").replace(/>+$/, "");
    }
  } catch {
    // best-effort message-id extraction
  }
  return null;
}

export async function importEmails({
  client,
  files,
  destinationMailboxId,
  conflictResolution,
  onProgress,
  signal,
}: {
  client: IJMAPClient;
  files: File[];
  destinationMailboxId: string;
  conflictResolution: ConflictResolution;
  onProgress?: (progress: ImportProgress) => void;
  signal?: AbortSignal;
}): Promise<ImportResult> {
  const result: ImportResult = { imported: 0, skipped: 0, failed: 0, errors: [] };
  const progress: ImportProgress = {
    total: 0,
    processed: 0,
    imported: 0,
    skipped: 0,
    failed: 0,
    currentFile: "",
  };

  const importables = await expandImportableEmails(files);
  progress.total = importables.length;
  onProgress?.({ ...progress });

  if (importables.length === 0) {
    return result;
  }

  const duplicateCheck = conflictResolution !== "copy";
  let existingMessageIds: Set<string> | null = null;

  if (duplicateCheck) {
    const messageIds: string[] = [];
    for (const item of importables) {
      if (signal?.aborted) break;
      const msgId = await extractMessageIdFromEml(item.blob);
      if (msgId) messageIds.push(msgId);
    }
    existingMessageIds = await findExistingMessageIds(client, messageIds);
  }

  for (const item of importables) {
    if (signal?.aborted) break;

    progress.currentFile = item.name;
    progress.processed++;
    onProgress?.({ ...progress });

    try {
      const msgId = await extractMessageIdFromEml(item.blob);
      if (duplicateCheck && msgId && existingMessageIds?.has(msgId)) {
        if (conflictResolution === "skip") {
          progress.skipped++;
          result.skipped++;
          onProgress?.({ ...progress });
          continue;
        }
      }

      let emlBlob = item.blob;

      try {
        const parsed = await parseEml(item.blob);
        emlBlob = generateRfc822FromParsed(parsed);
      } catch {
      // best-effort dedup lookup
      }

      const file = new File([emlBlob], item.name, { type: "message/rfc822" });
      const { blobId } = await client.uploadBlob(file);

      await client.importEmail(
        blobId,
        { [destinationMailboxId]: true },
        { "$seen": true },
      );

      progress.imported++;
      result.imported++;
    } catch (err) {
      progress.failed++;
      result.failed++;
      result.errors.push({
        file: item.name,
        error: err instanceof Error ? err.message : "Unknown error",
      });
    }

    onProgress?.({ ...progress });
  }

  return result;
}