// Main deletion function that initiates the process
export const deleteResource = mutation({
  args: { resourceId: v.id("resources") },
  handler: async (ctx, { resourceId }) => {
    const userId = await ctx.auth.getUserId();
    if (!userId) throw new Error("Authentication required");

    // Verify permissions
    const resource = await ctx.db.get(resourceId);
    if (!resource) throw new Error("Resource not found");
    if (!await hasPermission(ctx, userId, resourceId, "delete")) {
      throw new Error("Not authorized");
    }

    // Start batch deletion process
    await ctx.scheduler.runAfter(0, internal.batchDelete, {
      resourceId,
      userId,
      cursor: null,
      phase: "items"
    });

    return { success: true };
  }
});

// Internal batch deletion handler
const batchDelete = internalMutation({
  args: {
    resourceId: v.id("resources"),
    userId: v.string(),
    cursor: v.optional(v.string()),
    phase: v.union(v.literal("items"), v.literal("metadata"), v.literal("cleanup"))
  },
  handler: async (ctx, { resourceId, userId, cursor, phase }) => {
    const BATCH_SIZE = 100;

    try {
      switch (phase) {
        case "items": {
          const items = await getBatch(ctx, "items", resourceId, BATCH_SIZE, cursor);
          await deleteItems(ctx, items.page);
          
          if (items.isDone) {
            await nextPhase(ctx, resourceId, userId, "metadata");
          } else {
            await continueBatch(ctx, resourceId, userId, items.cursor, "items");
          }
          break;
        }

        case "metadata": {
          const metadata = await getBatch(ctx, "metadata", resourceId, BATCH_SIZE, cursor);
          await deleteMetadata(ctx, metadata.page);
          
          if (metadata.isDone) {
            await nextPhase(ctx, resourceId, userId, "cleanup");
          } else {
            await continueBatch(ctx, resourceId, userId, metadata.cursor, "metadata");
          }
          break;
        }

        case "cleanup": {
          await ctx.db.delete(resourceId);
          break;
        }
      }
    } catch (error) {
      await logError(ctx, resourceId, `Failed during ${phase}: ${error.message}`);
      throw error;
    }
  }
});

// Helper functions
async function getBatch(ctx, table, resourceId, size, cursor) {
  return await ctx.db
    .query(table)
    .withIndex("by_resource", q => q.eq("resourceId", resourceId))
    .paginate({ numItems: size, cursor: cursor ?? null });
}

async function nextPhase(ctx, resourceId, userId, nextPhase) {
  await ctx.scheduler.runAfter(0, internal.batchDelete, {
    resourceId,
    userId,
    cursor: null,
    phase: nextPhase
  });
}

async function continueBatch(ctx, resourceId, userId, cursor, currentPhase) {
  await ctx.scheduler.runAfter(0, internal.batchDelete, {
    resourceId,
    userId,
    cursor,
    phase: currentPhase
  });
}

// Main deletion function that initiates the process
export const deleteResource = mutation({
  args: { resourceId: v.id("resources") },
  handler: async (ctx, { resourceId }) => {
    const userId = await ctx.auth.getUserId();
    if (!userId) throw new Error("Authentication required");

    // Verify permissions
    const resource = await ctx.db.get(resourceId);
    if (!resource) throw new Error("Resource not found");
    if (!await hasPermission(ctx, userId, resourceId, "delete")) {
      throw new Error("Not authorized");
    }

    // Start batch deletion process
    await ctx.scheduler.runAfter(0, internal.batchDelete, {
      resourceId,
      userId,
      cursor: null,
      phase: "items"
    });

    return { success: true };
  }
});

// Internal batch deletion handler
const batchDelete = internalMutation({
  args: {
    resourceId: v.id("resources"),
    userId: v.string(),
    cursor: v.optional(v.string()),
    phase: v.union(v.literal("items"), v.literal("metadata"), v.literal("cleanup"))
  },
  handler: async (ctx, { resourceId, userId, cursor, phase }) => {
    const BATCH_SIZE = 100;

    try {
      switch (phase) {
        case "items": {
          const items = await getBatch(ctx, "items", resourceId, BATCH_SIZE, cursor);
          await deleteItems(ctx, items.page);
          
          if (items.isDone) {
            await nextPhase(ctx, resourceId, userId, "metadata");
          } else {
            await continueBatch(ctx, resourceId, userId, items.cursor, "items");
          }
          break;
        }

        case "metadata": {
          const metadata = await getBatch(ctx, "metadata", resourceId, BATCH_SIZE, cursor);
          await deleteMetadata(ctx, metadata.page);
          
          if (metadata.isDone) {
            await nextPhase(ctx, resourceId, userId, "cleanup");
          } else {
            await continueBatch(ctx, resourceId, userId, metadata.cursor, "metadata");
          }
          break;
        }

        case "cleanup": {
          await ctx.db.delete(resourceId);
          break;
        }
      }
    } catch (error) {
      await logError(ctx, resourceId, `Failed during ${phase}: ${error.message}`);
      throw error;
    }
  }
});

// Helper functions
async function getBatch(ctx, table, resourceId, size, cursor) {
  return await ctx.db
    .query(table)
    .withIndex("by_resource", q => q.eq("resourceId", resourceId))
    .paginate({ numItems: size, cursor: cursor ?? null });
}

async function nextPhase(ctx, resourceId, userId, nextPhase) {
  await ctx.scheduler.runAfter(0, internal.batchDelete, {
    resourceId,
    userId,
    cursor: null,
    phase: nextPhase
  });
}

async function continueBatch(ctx, resourceId, userId, cursor, currentPhase) {
  await ctx.scheduler.runAfter(0, internal.batchDelete, {
    resourceId,
    userId,
    cursor,
    phase: currentPhase
  });
}