import { NextRequest, NextResponse } from "next/server";
import { auth } from "@/auth";
import { db } from "@/lib/db";
import {
  parseFilename,
  stripVersionFromTitle,
  findMatchingShotCode,
} from "@/lib/batch-upload-parser";

export type PreviewItemStatus =
  | "new-version"       // task found, same version prefix → just add a version
  | "rename-and-upload" // task found but different version → rename task + add version
  | "create-task"       // no matching task → use/rename fallback "Comp" task or create new
  | "update-highres"    // .mov file → replace the shot's high-res file
  | "no-shot"           // shot code not found in this project
  | "unsupported";      // file extension is not .mp4 or .mov

export interface PreviewItem {
  fileName: string;
  status: PreviewItemStatus;
  shotId: string | null;
  shotCode: string | null;
  /** For .mp4: ID of the directly matched task, if found */
  taskId: string | null;
  /** For .mp4: current title of the matched / fallback task */
  currentTaskTitle: string | null;
  /** For .mp4: desired task title after upload (filename without extension) */
  newTaskTitle: string;
  /** For .mov: filename of the existing high-res file that will be replaced */
  currentHighResFilename: string | null;
  /** For create-task: ID of a "Comp" task to rename & use */
  fallbackTaskId: string | null;
  fallbackTaskTitle: string | null;
}

/**
 * POST /api/batch-upload/preview
 * Body: { projectId: string; fileNames: string[] }
 *
 * Returns a preview of what action will be taken for each file, without
 * actually uploading anything.
 */
export async function POST(req: NextRequest) {
  const session = await auth();
  if (!session?.user) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }

  let body: unknown;
  try {
    body = await req.json();
  } catch {
    return NextResponse.json({ error: "Invalid JSON" }, { status: 400 });
  }

  const { projectId, fileNames } = body as {
    projectId?: string;
    fileNames?: unknown;
  };

  if (!projectId || !Array.isArray(fileNames) || fileNames.length === 0) {
    return NextResponse.json(
      { error: "projectId and fileNames[] are required" },
      { status: 400 }
    );
  }

  // Load all shots for this project with their tasks
  const shots = await db.shot.findMany({
    where: { projectId },
    select: {
      id: true,
      shotCode: true,
      highResFilename: true,
      tasks: {
        select: { id: true, title: true, type: true },
        orderBy: { sortOrder: "asc" },
      },
    },
  });

  const shotCodes = shots.map((s) => s.shotCode);

  const items: PreviewItem[] = fileNames.map((fileName: string) => {
    const parsed = parseFilename(fileName);

    if (parsed.type === "other") {
      return {
        fileName,
        status: "unsupported" as const,
        shotId: null,
        shotCode: null,
        taskId: null,
        currentTaskTitle: null,
        newTaskTitle: "",
        currentHighResFilename: null,
        fallbackTaskId: null,
        fallbackTaskTitle: null,
      };
    }

    // Find the shot whose code is a prefix of this file's task name base
    const matchedCode = findMatchingShotCode(parsed.taskNameBase, shotCodes);
    const matchedShot = matchedCode
      ? shots.find((s) => s.shotCode === matchedCode) ?? null
      : null;

    if (!matchedShot) {
      return {
        fileName,
        status: "no-shot" as const,
        shotId: null,
        shotCode: null,
        taskId: null,
        currentTaskTitle: null,
        newTaskTitle: "",
        currentHighResFilename: null,
        fallbackTaskId: null,
        fallbackTaskTitle: null,
      };
    }

    // ── .mov → update-highres ─────────────────────────────────────────────
    if (parsed.type === "mov") {
      return {
        fileName,
        status: "update-highres" as const,
        shotId: matchedShot.id,
        shotCode: matchedShot.shotCode,
        taskId: null,
        currentTaskTitle: null,
        newTaskTitle: "",
        currentHighResFilename: matchedShot.highResFilename ?? null,
        fallbackTaskId: null,
        fallbackTaskTitle: null,
      };
    }

    // ── .mp4 → find matching task ─────────────────────────────────────────
    const desiredTitle = parsed.taskNameWithVersion; // full name without ext

    // Match by stripping version from existing task titles
    const matchedTask = matchedShot.tasks.find(
      (t) => stripVersionFromTitle(t.title) === parsed.taskNameBase
    );

    if (matchedTask) {
      const sameTitle = matchedTask.title === desiredTitle;
      return {
        fileName,
        status: (sameTitle ? "new-version" : "rename-and-upload") as PreviewItemStatus,
        shotId: matchedShot.id,
        shotCode: matchedShot.shotCode,
        taskId: matchedTask.id,
        currentTaskTitle: matchedTask.title,
        newTaskTitle: desiredTitle,
        currentHighResFilename: null,
        fallbackTaskId: null,
        fallbackTaskTitle: null,
      };
    }

    // No direct match – look for a generic "Comp" or "comp" task, or any COMP type
    const compTask = matchedShot.tasks.find(
      (t) =>
        t.title.toLowerCase() === "comp" ||
        t.type === "COMP"
    );

    return {
      fileName,
      status: "create-task" as const,
      shotId: matchedShot.id,
      shotCode: matchedShot.shotCode,
      taskId: null,
      currentTaskTitle: null,
      newTaskTitle: desiredTitle,
      currentHighResFilename: null,
      fallbackTaskId: compTask?.id ?? null,
      fallbackTaskTitle: compTask?.title ?? null,
    };
  });

  return NextResponse.json({ items });
}