/// The MIT License (MIT)

/// Copyright (c) 2016 Bazinga Technologies Inc

module internal FSharp.Data.GraphQL.Validation

open FSharp.Data.GraphQL.Types

open FSharp.Data.GraphQL.Types.Patterns

type ValidationResult =

| Success

| Error of string list

let (@) res1 res2 =

match res1, res2 with

| Success, Success -> Success

| Success, _ -> res2

| _, Success -> res1

| Error e1, Error e2 -> Error (e1 @ e2)

let validateImplements (objdef: ObjectDef) (idef: InterfaceDef) =

let objectFields =

objdef.Fields

let errors =

idef.Fields

|> Array.fold (fun acc f ->

match Map.tryFind f.Name objectFields with

| None -> (sprintf "'%s' field is defined by interface %s, but not implemented in object %s" f.Name idef.Name objdef.Name)::acc

| Some objf when objf = f -> acc

| Some _ -> (sprintf "'%s.%s' field signature does not match it's definition in interface %s" objdef.Name f.Name idef.Name)::acc) []

match errors with

| [] -> Success

| err -> Error err

let validateType (namedTypes: Map<string, NamedDef>) typedef =

match typedef with

| Scalar scalardef -> Success

| Object objdef ->

let nonEmptyResult = if objdef.Fields.Count > 0 then Success else Error [ objdef.Name + " must have at least one field defined" ]

let implementsResult =

objdef.Implements

|> Array.fold (fun acc i -> acc @ validateImplements objdef i) Success

nonEmptyResult @ implementsResult

| InputObject indef ->

let nonEmptyResult = if indef.Fields.Length > 0 then Success else Error [ indef.Name + " must have at least one field defined" ]

nonEmptyResult

| Union uniondef ->

let nonEmptyResult = if uniondef.Options.Length > 0 then Success else Error [ uniondef.Name + " must have at least one type definition option" ]

nonEmptyResult

| Enum enumdef ->

let nonEmptyResult = if enumdef.Options.Length > 0 then Success else Error [ enumdef.Name + " must have at least one enum value defined" ]

nonEmptyResult

| Interface idef ->

let nonEmptyResult = if idef.Fields.Length > 0 then Success else Error [ idef.Name + " must have at least one field defined" ]

nonEmptyResult

| _ -> failwithf "Unexpected value of typedef: %O" typedef

let validate (namedTypes: Map<string, NamedDef>) : ValidationResult =

namedTypes

|> Map.toArray

|> Array.map snd

|> Array.fold (fun acc namedDef -> acc @ validateType namedTypes namedDef) Success