/*
 * Copyright (C) 2023 Simon Bruder
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package catering.inventory;

import org.salespointframework.catalog.Product;
import org.salespointframework.inventory.UniqueInventory;
import org.salespointframework.inventory.UniqueInventoryItem;
import org.springframework.security.access.prepost.PreAuthorize;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.util.Assert;
import org.springframework.validation.Errors;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;

import catering.catalog.CateringCatalog;
import catering.catalog.Consumable;
import catering.catalog.Rentable;
import jakarta.validation.Valid;

/*
 * TODO TL;DR: Use HandlerMethodArgumentResolver
 *
 * This class currently has many confusing methods that do a variety of things,
 * but mostly work around polymorphic restrictions of Spring.
 * Ideally, spring would allow a form to be polymorphic
 * based on its attributes, if they are unique,
 * or based on another parameter.
 * From what I could find,
 * this is not possible without implementing a custom HandlerMethodArgumentResolver.
 * If there is time, the controller should be changed to use this,
 * which should vastly simplify it.
 *
 * Adding will always require a type parameter,
 * as the type is not known at first.
 * However, currently there are two (or even three) POST handlers,
 * as there are two different form types it must support
 * (and an infinite amount of invalid types that it should ignore).
 *
 * Editing should not require passing any additional type parameter around
 * as the type can be inferred from the product.
 * Changing the type of a product should not be possible.
 */

@Controller
@PreAuthorize("hasRole('ADMIN')")
class InventoryController {
	private final UniqueInventory<UniqueInventoryItem> inventory;
	private final CateringCatalog cateringCatalog;

	InventoryController(UniqueInventory<UniqueInventoryItem> inventory, CateringCatalog cateringCatalog) {
		Assert.notNull(inventory, "Inventory must not be null!");
		Assert.notNull(inventory, "CateringCatalog must not be null!");
		this.inventory = inventory;
		this.cateringCatalog = cateringCatalog;
	}

	/**
	 * Lists all inventory products.
	 *
	 * @param model an instance of {@link Model}
	 * @return the inventory template
	 */
	@GetMapping("/inventory")
	String list(Model model) {
		model.addAttribute("inventory", inventory.findAll());

		return "inventory";
	}

	/**
	 * Returns the edit page for an inventory product.
	 *
	 * @param model an instance of {@link Model}
	 * @param pid   the {@link Product} to edit
	 * @return the inventory-mutate template with the {@link Product} data prefilled
	 */
	@GetMapping("/inventory/edit/{pid}")
	String edit(Model model, @PathVariable Product pid) {
		UniqueInventoryItem item = inventory.findByProduct(pid).get();
		final InventoryMutateForm form = InventoryMutateForm.of(pid, item);

		return edit(model, form);
	}

	/**
	 * Returns the edit page for an inventory product.
	 *
	 * This method is not mapped,
	 * but is used by other methods to generalise the display of the edit page.
	 *
	 * @param model an instance of {@link Model}
	 * @param form  an already filled or empty {@link InventoryMutateForm}
	 * @return the inventory-mutate template with the {@link InventoryMutateForm}
	 *         data prefilled
	 */
	String edit(Model model, InventoryMutateForm form) {
		model.addAttribute("actionIsAdd", false);
		model.addAttribute("form", form);

		return "inventory-mutate";
	}

	/**
	 * Edits a consumable.
	 *
	 * @param form   a user-filled {@link ConsumableMutateForm}
	 * @param errors an {@link Errors} object including validation errors
	 * @param pid    the {@link Product} to edit
	 * @param model  an instance of {@link Model}
	 * @return a redirect on success, otherwise the filled form with all errors
	 *         highlighted
	 */
	@PostMapping(path = "/inventory/edit/{pid}", params = "type=Consumable")
	String editConsumable(@Valid @ModelAttribute("form") ConsumableMutateForm form, Errors result,
			@PathVariable Consumable pid, Model model) {
		return edit(form, result, pid, model);
	}

	/**
	 * Edits a rentable.
	 *
	 * @param form   a user-filled {@link RentableMutateForm}
	 * @param errors an {@link Errors} object including validation errors
	 * @param pid    the {@link Product} to edit
	 * @param model  an instance of {@link Model}
	 * @return a redirect on success, otherwise the filled form with all errors
	 *         highlighted
	 */
	@PostMapping(path = "/inventory/edit/{pid}", params = "type=Rentable")
	String editRentable(@Valid @ModelAttribute("form") RentableMutateForm form, Errors result,
			@PathVariable Rentable pid, Model model) {
		return edit(form, result, pid, model);
	}

	/**
	 * Edits an inventory product.
	 *
	 * This method is not mapped,
	 * but is used by
	 * {@link #editConsumable(ConsumableMutateForm, Errors, Consumable, Model)}
	 * and {@link #editRentable(RentableMutateForm, Errors, Rentable, Model)}
	 * to generalise the editing of products.
	 *
	 * @param form    a user-filled {@link RentableMutateForm}
	 * @param errors  an {@link Errors} object including validation errors
	 * @param product the {@link Product} to edit
	 * @param model   an instance of {@link Model}
	 * @return a redirect on success, otherwise the filled form with all errors
	 *         highlighted
	 */
	String edit(InventoryMutateForm form, Errors result, Product product, Model model) {
		if (result.hasErrors()) {
			return edit(model, form);
		}

		form.modifyProduct(product);
		product = cateringCatalog.save(product);

		UniqueInventoryItem item = inventory.findByProduct(product).get();
		// no setQuantity in enterprise java
		// (though returing a modified object is actually nice)
		inventory.save(item.increaseQuantity(form.getQuantity().subtract(item.getQuantity())));
		return "redirect:/inventory";
	}

	/**
	 * Returns the add page for a new inventory product.
	 *
	 * @param model an instance of {@link org.springframework.ui.Model}
	 * @param type  string representation of a {@link Product} subclass supported by
	 *              {@link InventoryMutateForm}
	 * @return the inventory-mutate template with no data prefilled
	 */
	@GetMapping(path = "/inventory/add")
	String add(Model model, @RequestParam String type) {
		switch (type) {
			case "Consumable":
				return add(model, new ConsumableMutateForm());
			case "Rentable":
				return add(model, new RentableMutateForm());
			default:
				// TODO better error handling
				return "redirect:/inventory";
		}
	}

	/**
	 * Returns the add page for a new inventory product.
	 *
	 * This method is not mapped,
	 * but is used by other methods to generalise the display of the add page.
	 *
	 * @param model an instance of {@link Model}
	 * @param form  an already filled or empty {@link InventoryMutateForm}
	 * @return the inventory-mutate template with the {@link InventoryMutateForm}
	 *         data prefilled
	 */
	String add(Model model, InventoryMutateForm form) {
		model.addAttribute("actionIsAdd", true);
		model.addAttribute("form", form);
		return "inventory-mutate";
	}

	/**
	 * Adds a consumable.
	 *
	 * @param form   a user-filled {@link ConsumableMutateForm}
	 * @param errors an {@link Errors} object including validation errors
	 * @param model  an instance of {@link Model}
	 * @return a redirect on success, otherwise the filled form with all errors
	 *         highlighted
	 */
	@PostMapping(path = "/inventory/add", params = "type=Consumable")
	String addConsumable(@Valid @ModelAttribute("form") ConsumableMutateForm form, Errors result, Model model) {
		return add(form, result, model);
	}

	/**
	 * Adds a rentable.
	 *
	 * @param form   a user-filled {@link RentableMutateForm}
	 * @param errors an {@link Errors} object including validation errors
	 * @param model  an instance of {@link Model}
	 * @return a redirect on success, otherwise the filled form with all errors
	 *         highlighted
	 */
	@PostMapping(path = "/inventory/add", params = "type=Rentable")
	String addRentable(@Valid @ModelAttribute("form") RentableMutateForm form, Errors result, Model model) {
		return add(form, result, model);
	}

	/**
	 * Adds an inventory product.
	 *
	 * @param form   a user-filled {@link InventoryMutateForm}
	 * @param errors an {@link Errors} object including validation errors
	 * @param model  an instance of {@link Model}
	 * @return a redirect on success, otherwise the filled form with all errors
	 *         highlighted
	 */
	String add(@Valid InventoryMutateForm form, Errors result, Model model) {
		if (result.hasErrors()) {
			return add(model, form);
		}
		inventory.save(new UniqueInventoryItem(cateringCatalog.save(form.toProduct()), form.getQuantity()));
		return "redirect:/inventory";
	}

	/**
	 * Deletes an inventory product.
	 *
	 * @param pid the {@link Product} to delete
	 * @return a redirect to the inventory overview
	 */
	@GetMapping("/inventory/delete/{pid}")
	String delete(@PathVariable Product pid) {
		UniqueInventoryItem item = inventory.findByProduct(pid).get();
		inventory.delete(item);
		cateringCatalog.delete(pid);
		return "redirect:/inventory";
	}
}