module RestApi open Newtonsoft.Json open System.Collections.Generic open Newtonsoft.Json.Linq type User(name : string, owes : SortedDictionary, owed_by : SortedDictionary) = member this.name = name member this.owes = owes member this.owed_by = owed_by member this.lend(name: string, amount: decimal) = let remaining = match owes.TryGetValue(name) with | (true,value) when value - amount > 0m -> owes.[name] <- (value - amount) 0m | (true,value) -> owes.Remove(name) |> ignore amount - value | (false,_) -> amount match owed_by.TryGetValue(name) with | (true,value) when remaining > 0m -> owed_by.[name] <- value + remaining | (false,_) when remaining > 0m -> owed_by.Add(name, remaining) | _ -> () member this.borrow(name: string, amount: decimal) = let remaining = match owed_by.TryGetValue(name) with | (true,value) when value - amount > 0m -> owed_by.[name] <- value - amount 0m | (true,value) -> owed_by.Remove(name) |> ignore amount - value | (false,_) -> amount match owes.TryGetValue(name) with | (true,value) when remaining > 0m -> owes.[name] <- value + remaining | (false,_) when remaining > 0m -> owes.Add(name, remaining) | _ -> () member this.balance = match (owes,owed_by) with | (null,null) -> 0m | (_,null) -> - (owes |> Seq.map (fun p -> p.Value) |> Seq.sum) | (null,_) -> (owed_by |> Seq.map (fun p -> p.Value) |> Seq.sum) | (_,_) -> -(owes |> Seq.map (fun p -> p.Value) |> Seq.sum) + (owed_by |> Seq.map (fun p -> p.Value) |> Seq.sum) type Database(users : User[]) = member this.users = users type IOU(lender: string, borrower: string, amount : decimal) = member this.lender = lender member this.borrower = borrower member this.amount = amount type RestApi(database : string) = let Source = JsonConvert.DeserializeObject(database) member this.Get(url: string) = JsonConvert.SerializeObject(Source) member this.Get(url: string, payload: string) = let jt = JToken.Parse(payload) let toGet = JsonConvert.DeserializeObject(jt.SelectToken("users").ToString()) let users = Source.users |> Seq.filter (fun p -> Seq.contains p.name toGet) |> Seq.toArray JsonConvert.SerializeObject(Database(users)) member this.Post(url: string, payload: string) = match url with | "/add" -> let userName = JToken.Parse(payload).SelectToken("user").ToString() let user = User(userName,SortedDictionary(),SortedDictionary()) JsonConvert.SerializeObject(user) | "/iou" -> let iou = JsonConvert.DeserializeObject(payload) let lender = Source.users |> Seq.find (fun p -> p.name.Equals(iou.lender)) lender.lend(iou.borrower,iou.amount) let borrower = Source.users |> Seq.find (fun p -> p.name.Equals(iou.borrower)) borrower.borrow(iou.lender,iou.amount) let newSource = [|lender ; borrower|] |> Seq.sortBy (fun p -> p.name) |> Seq.toArray JsonConvert.SerializeObject(Database(newSource)) | _ -> failwith "unsupported url"