defmodule LLMDB.Provider do
  @moduledoc """
  Provider struct with Zoi schema validation.

  Represents an LLM provider with metadata including identity, base URL,
  environment variables, documentation, and pricing defaults.

  ## Fields

  - `:id` - Unique provider identifier atom (e.g., `:openai`)
  - `:name` - Display name
  - `:base_url` - Base API URL (supports template variables like `{region}`)
  - `:env` - List of environment variable names for credentials
  - `:config_schema` - Runtime configuration field definitions
  - `:doc` - Documentation URL
  - `:pricing_defaults` - Default pricing components applied to all models (see below)
  - `:exclude_models` - Model IDs to exclude from upstream sources
  - `:extra` - Additional provider-specific data
  - `:alias_of` - Primary provider ID if this is an alias

  ## Pricing Defaults

  The `:pricing_defaults` field defines default pricing for tools and features
  that apply to all models from this provider. This avoids duplicating tool
  pricing across every model definition.

      %{
        currency: "USD",
        components: [
          %{id: "tool.web_search", kind: "tool", tool: "web_search", unit: "call", per: 1000, rate: 10.0},
          %{id: "storage.vectors", kind: "storage", unit: "gb_day", per: 1, rate: 0.10}
        ]
      }

  Provider defaults are merged with model-specific pricing at load time.
  See `LLMDB.Pricing` and the [Pricing and Billing guide](pricing-and-billing.md).
  """

  @config_field_schema Zoi.object(%{
                         name: Zoi.string(),
                         type: Zoi.string(),
                         required: Zoi.boolean() |> Zoi.default(false),
                         default: Zoi.any() |> Zoi.nullish(),
                         doc: Zoi.string() |> Zoi.nullish()
                       })

  @pricing_component_schema Zoi.object(%{
                              id: Zoi.string(),
                              kind:
                                Zoi.enum([
                                  "token",
                                  "tool",
                                  "image",
                                  "storage",
                                  "request",
                                  "other"
                                ])
                                |> Zoi.nullish(),
                              unit:
                                Zoi.enum([
                                  "token",
                                  "call",
                                  "query",
                                  "session",
                                  "gb_day",
                                  "image",
                                  "source",
                                  "other"
                                ])
                                |> Zoi.nullish(),
                              per: Zoi.integer() |> Zoi.min(1) |> Zoi.nullish(),
                              rate: Zoi.number() |> Zoi.nullish(),
                              meter: Zoi.string() |> Zoi.nullish(),
                              tool: Zoi.union([Zoi.atom(), Zoi.string()]) |> Zoi.nullish(),
                              size_class: Zoi.string() |> Zoi.nullish(),
                              notes: Zoi.string() |> Zoi.nullish()
                            })

  @pricing_defaults_schema Zoi.object(%{
                             currency: Zoi.string() |> Zoi.nullish(),
                             components: Zoi.array(@pricing_component_schema) |> Zoi.default([])
                           })

  @schema Zoi.struct(
            __MODULE__,
            %{
              id: Zoi.atom(),
              name: Zoi.string() |> Zoi.nullish(),
              base_url: Zoi.string() |> Zoi.nullish(),
              env: Zoi.array(Zoi.string()) |> Zoi.nullish(),
              config_schema: Zoi.array(@config_field_schema) |> Zoi.nullish(),
              doc: Zoi.string() |> Zoi.nullish(),
              exclude_models: Zoi.array(Zoi.string()) |> Zoi.default([]) |> Zoi.nullish(),
              pricing_defaults: @pricing_defaults_schema |> Zoi.nullish(),
              extra: Zoi.map() |> Zoi.nullish(),
              alias_of: Zoi.atom() |> Zoi.nullish()
            },
            coerce: true
          )

  @type t :: unquote(Zoi.type_spec(@schema))

  @enforce_keys Zoi.Struct.enforce_keys(@schema)
  defstruct Zoi.Struct.struct_fields(@schema)

  @doc "Returns the Zoi schema for Provider"
  def schema, do: @schema

  @doc """
  Creates a new Provider struct from a map, validating with Zoi schema.

  ## Examples

      iex> LLMDB.Provider.new(%{id: :openai, name: "OpenAI"})
      {:ok, %LLMDB.Provider{id: :openai, name: "OpenAI"}}

      iex> LLMDB.Provider.new(%{})
      {:error, _validation_errors}
  """
  @spec new(map()) :: {:ok, t()} | {:error, term()}
  def new(attrs) when is_map(attrs) do
    Zoi.parse(@schema, attrs)
  end

  @doc """
  Creates a new Provider struct from a map, raising on validation errors.

  ## Examples

      iex> LLMDB.Provider.new!(%{id: :openai, name: "OpenAI"})
      %LLMDB.Provider{id: :openai, name: "OpenAI"}
  """
  @spec new!(map()) :: t()
  def new!(attrs) when is_map(attrs) do
    case new(attrs) do
      {:ok, provider} -> provider
      {:error, reason} -> raise ArgumentError, "Invalid provider: #{inspect(reason)}"
    end
  end
end

defimpl DeepMerge.Resolver, for: LLMDB.Provider do
  @moduledoc false

  def resolve(original, override = %LLMDB.Provider{}, resolver) do
    cleaned_override =
      override
      |> Map.from_struct()
      |> Enum.reject(fn {_key, value} -> is_nil(value) end)
      |> Map.new()

    Map.merge(original, cleaned_override, resolver)
  end

  def resolve(original, override, resolver) when is_map(override) do
    Map.merge(original, override, resolver)
  end

  def resolve(_original, override, _resolver), do: override
end