Merge pull request #2353 from benjaminwil/shipments_documentation

Shipments documentation

guides/shipments/cartons.md

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+# Cartons
+
+The `Spree::Carton` model represents how an order was shipped. For stores that
+use third-party logistics or complicated warehouse workflows, the shipment
+described when the order is confirmed may not be how the _actual_ shipment is
+packaged when it leaves its destination.
+
+## Example of usage
+
+**A customer orders two t-shirts.**
+
+Solidus creates one `Spree::Shipment` object, which is used to ship both
+t-shirts in the order as one package.
+
+**The customer is charged for a single shipment.**
+
+Your t-shirt warehouse receives the shipping instructions for the new order.
+However, they realize that one of the t-shirts is currently backordered. They
+cannot send both t-shirts in a single package.
+
+**The warehouse ship the first of two packages, which is the first of two
+t-shirts.**
+
+However, you do not want to charge the customer for a second shipment. Your
+inventory was not accurate, and your store is paying for the additional package.
+
+If you split the shipment into two `Spree::Shipment` objects, the customer would
+be charged shipping for both packages.
+
+To avoid an extra shipping charge, you can instead create additional
+`Spree::Carton` objects for every package sent out of the warehouse. This way,
+the shipment object stays unique and the order total does not change.
+
+**The warehouse ships the second of two packages.**
+
+This second package is associated with the order as another `Spree::Carton`
+object. Although it is shipped as a separate package, the customer is not
+charged for another shipment.
+
+<!-- TODO:
+  This article is a stub.
+-->

guides/shipments/custom-shipping-calculators.md

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+# Custom shipping calculators
+
+This article provides context about creating custom shipping calculators in the
+case that the provided calculators do not meet your store's needs.
+
+## Pre-configured calculators
+
+Before developing a custom calculator, you should make sure that the calculator
+you need doesn't already exist in Solidus or one of its extensions.
+
+Solidus comes with a set of default calculators that account for typical
+shipping scenarios:
+
+- [Flat percent](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/flat_percent_item_total.rb)
+- [Flat rate (per order)](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/flat_rate.rb)
+- [Flat rate per package item](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/per_item.rb)
+- [Flexible rate per package item](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/flexi_rate.rb)
+- [Price sack](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/price_sack.rb)
+
+If the calculators that come with Solidus are not enough for your needs, you
+might want to use an extension like
+[`solidus_active_shipping`][solidus-active-shipping] that provides additional
+API-based rate calculation functionality for common carriers like UPS, USPS, and
+FedEx. Alternatively, you could develop your own custom calculator.
+
+[solidus-active-shipping]: solidus-active-shipping-extension.md
+
+## Custom calculator requirements
+
+A custom calculator should accept a `Spree::Stock::Package` (a `package`) and
+return a cost.
+
+Use the `package.order` method to access the current order's information, and
+the `package.contents` methods to access the current package's contents. As a
+developer, you should always deal with the `package.contents`. Otherwise, you
+may be quoting an entire order when you only want to quote one of many shipments
+on an order.
+
+<!-- TODO:
+  So far, the shipments documentation doesn't go into packages in any details.
+  These references by themselves are not enough. What is the purpose of a
+  "package" that is distinctive from a "shipment".
+-->
+
+Typically, a calculator uses the following order information:
+
+- The `Spree::Address` used as the order's shipping address.
+- The `Spree::LineItem` objects associated with the order.
+- The `Spree::Variant` product information (such as the weight and dimensions)
+  associated with each line item in the order.
+
+For an example of a typical calculator, we recommend reading the source code for
+Solidus's [stock flat rate calculator][flat-rate-source]. For a more complicated
+example of what is possible with custom calculators, see the
+[`solidus_active_shipping` base calculator][base-calculator-source]. This
+calculator collects enough information about an order to send to a carrier and
+get a rate quote back.
+
+[flat-rate-source]: https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/flat_rate.rb
+[base-calculator-source]: https://github.com/solidusio-contrib/solidus_active_shipping/blob/master/app/models/spree/calculator/shipping/active_shipping/base.rb
+
+## Use additional product information
+
+In addition to providing relevant information about shipping addresses and
+product variants, you can use information about the product itself to inform a
+calculator's results. A product's tax category or shipping category could be
+meaningful information for shipping calculations. By default, each package
+contains only items in the same shipping category.
+
+For example, you might want your calculator to handle your product with a
+shipping category of "Oversized" differently than it would a product with the
+"Default" shipping category.
+
+<!-- TODO:
+  Add an example code block or a link to some Solidus code that shows a
+  calculator taking advantage of shipping categories and/or tax categories to
+  produce a specific result.
+-->
+

guides/shipments/overview-of-shipments.md

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+# Overview of shipments
+
+Solidus uses a flexible system to calculate shipping. It accommodates the full
+range of shipment pricing: from simple [flat
+rate](https://en.wikipedia.org/wiki/Flat_rate) calculations to more
+complex calculations related to product weight or type, the customer's shipping
+address, what shipping method is being used, and so on.
+
+If your store has complex shipping needs, you may find one of Solidus's existing
+shipping extensions, like [`solidus_active_shipping`][solidus-active-shipping]
+or [`solidus_shipstation`][solidus-shipstation], useful. Check out [the list of
+supported Solidus Extensions](https://extensions.solidus.io).
+
+This article provides a summary of shipping concepts. If you are interested in
+reading about example Solidus shipment setups see
+[Shipment setup examples](shipment-setup-examples.md).
+
+<!-- TODO:
+  Add section that summarizes what Spree::Objects are created related to
+  shipments and explains what their function is in the larger checkout process.
+-->
+
+[solidus-active-shipping]: solidus-active-shipping-extension.md
+[solidus-shipstation]: https://github.com/boomerdigital/solidus_shipstation
+
+## Shipment attributes
+
+The `Spree::Shipment` model tracks how items should be delivered to the
+customer. Developers may be interested in the following attributes:
+
+- `number`: The unique identifier for this shipment. It begins with the letter
+  `H` and ends in an 11-digit number. This number is visible to customers, and
+  it can be used to find the order (by calling `Spree::Shipment.find_by(number:
+  H12345678910)`).
+- `tracking`: The identifier given for the shipping provider (such as FedEx or
+  UPS).
+- `shipped_at`: The time when the shipment is shipped.
+- `state`: The current state of the shipment. See [Shipping
+  states](#shipping-states) for more information.
+- `stock_location_id`: The ID of the stock location where the items for this
+  shipment are sourced from.
+- `adjustment_total`: The sum of the promotion and tax adjustments on the
+  shipment.
+- `additional_tax_total`: The sum of U.S.-style sales taxes on the shipment.
+- `promo_total`: The sum of the promotions on the shipment.
+- `included_tax_total`: The sum of the VAT-style taxes on the shipment.
+- `cost`: The estimated shipping cost (for the selected shipping method).
+- `order_id`: The ID for the order that the shipment belongs to.
+
+<!-- TODO:
+  Add a shipment process flow diagram.
+-->
+
+### Shipping states
+
+Each shipment is assigned a `state` attribute. Depending on its state, different
+actions can be performed on shipments. There are four possible states:
+
+- `pending`: The shipment has backordered inventory units and/or the order is
+  not paid for.
+- `ready`: The shipment has no backordered inventory units and the order is paid
+  for.
+- `shipped`: The shipment has left the stock location.
+- `canceled`: When an order is cancelled, all of its shipments will also be
+  cancelled. When this happens, all items in the shipment will be restocked. If
+  an order is "resumed", then the shipment will also be resumed.
+
+## Core concepts
+
+To leverage Solidus's shipping system, become familiar with its key concepts:
+
+- Stock locations
+- Shipping methods
+- Zones
+- Shipping categories
+- Shipping calculators
+- Shipping rates
+- Inventory units
+- Cartons
+
+### Stock locations
+
+Stock locations represent physical storage locations from which stock is
+shipped.
+
+### Shipping methods
+
+Shipping methods identify the actual delivery services used to ship the
+product. For example:
+
+- UPS Ground
+- UPS One Day
+- FedEx 2Day
+- FedEx Overnight
+- DHL International
+
+Each shipping method is only applicable to a specific geographic
+zone. For example, you wouldn't be able to get a package delivered
+internationally using a domestic-only shipping method. You can't ship from
+Dallas, USA, to Rio de Janeiro, Brazil, using UPS Ground, which is a United
+States-only carrier.
+
+### Shipping categories
+
+You can further restrict when shipping methods are available to customers by
+using shipping categories. If you assign two products to two different shipping
+categories, you could ensure that these items are always sent as separate
+shipments.
+
+For example, if your store can only ship oversized products via a specific
+carrier, called "USPS Oversized Parcels", then you could create a shipping
+category called "Oversized" for that shipping method, which can then be assigned
+to oversized products.
+
+Shipping categories are created in the admin interface (**Settings -> Shipping
+-> Shipping Categories**) and then assigned to products (**Products -> Edit**).
+
+### Zones
+
+Zones serve as a mechanism for grouping distinct geographic areas together.
+
+The shipping address entered during checkout defines the zone (or zones) for the
+order. The zone limits the available shipping methods for the order. It also
+defines regional taxation rules.
+
+<!-- TODO:
+  For more information about zones, see [the Locations guide](../locations).
+-->
+
+### Shipping calculators
+
+A shipping calculator is the component responsible for calculating the shipping
+rate for each available shipping method.
+
+Solidus ships with five default shipping calculators:
+
+- [Flat percent](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/flat_percent_item_total.rb)
+- [Flat rate (per order)](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/flat_rate.rb)
+- [Flat rate per package item](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/per_item.rb)
+- [Flexible rate per package item](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/flexi_rate.rb)
+- [Price sack](https://github.com/solidusio/solidus/blob/master/core/app/models/spree/calculator/shipping/price_sack.rb)
+  (which offers variable shipping cost that depends on order total)
+
+If you want to estimate shipping rates using carrier APIs, You can use an
+extension like [`solidus_active_shipping`][solidus-active-shipping]. Or, if you
+have other complex needs, you can create a [custom shipping
+calculators][custom-shipping-calculators] for more information.
+
+[custom-shipping-calculators]: custom-shipping-calculators.md
+
+### Shipping rates
+
+For each shipment, a `Spree::ShippingRate` object is created for each of your
+store's shipping methods. These objects represent the cost of the shipment as
+calculated by each shipping method's calculator.
+
+| `Spree::ShippingRate` | 1     | 2     | 3     | Description                                         |
+|-----------------------|-------|-------|-------|-----------------------------------------------------|
+| `shipment_id`         | 1     | 1     | 1     | All of these rates are for one shipment             |
+| `shipping_method_id`  | 1     | 2     | 3     | Each available shipping method                      |
+| `selected`            | false | true  | false | Set to `true` for the selected shipping method only |
+| `cost`                | $0.50 | $1.75 | $1.25 | The shipment's shipping rate                        |
+
+Once the shipping method has been chosen, the matching `Spree::ShippingRate`'s
+`selected` key becomes `true`. Only one shipping rate can be `selected` for each
+shipment.
+
+### Inventory units
+
+A `Spree::InventoryUnit` is created for each item in a shipment. It tracks
+whether the item has shipped, what product variant the item is, and what order
+and shipment the item is associated with.
+
+<!-- TODO:
+  This section is a stub. It may be worth revisiting inventory units in detail,
+  or in its own article.
+-->
+
+### Cartons
+
+The `Spree::Carton` model represents how an order was shipped. For stores that
+use third-party logistics or complicated warehouse workflows, the shipment
+described when the order is confirmed may not be how the _actual_ shipment is
+packaged when it leaves its destination.
+
+For more information, see the [Cartons](cartons.md) article.