llm.bend source
llm.bend on the hub · documented module
# LLM client for the Anthropic Messages and OpenAI Chat Completions APIs, with SSE streaming. Source: https://github.com/paymog/bend-kit/tree/main/llmimport Baseimport ./sse.bend as Sseimport bend-kit-hairpin@0.3.0.0/hairpin.bend as Hairpinimport bend-kit-hairpin@0.3.0.0/retry.bend as Retryimport bend-kit-http@0.32.0.0/http.bend as Http# By hash, as http imports them: bend-kit-json@0.5.0.1, -bytes@0.3.0.0, -encoding@0.3.0.0.import 0x584fc27920487ceab242392391418d7f/json.bend as Jsonimport 0x49814d83de8f70993a43e1002be29ecd/bytes.bend as Bytesimport 0xcfc8be7b076f41f95c8e118383892d55/encoding.bend as Enc# Anthropic: POST {base}/v1/messages. OpenAI: POST {base}/chat/completions, which many other providers serve too.type Api is Data: Anthropic{} OpenAI{}type Role is Data: User{} Assistant{}type Msg is Data: Msg{role: Role, text: String}# system: "" for none. max: the most tokens to write.type Req is Data: Req{model: String, system: String, msgs: List<&2, Msg>, max: U32}# stop: the API's reason, as "end_turn" or "stop". input and output count tokens.type Reply is Data: Reply{id: String, model: String, text: String, stop: String, input: U32, output: U32}# ErrNet: the request did not complete, or Hairpin's breaker admitted no attempt. ErrApi: the API refused, with# its status and error text; an error event in a stream has status 200. ErrReply: a reply that is not the API's JSON, with its text.type Err is Data: ErrNet{e: Hairpin.Err} ErrApi{status: U32, body: String} ErrReply{body: String}# headers go on every request. ms: the step timeout. retries: extra tries after a retryable failure.type Client is Type: Client{api: Api, base: String, headers: Map<&2, List<&2, String>>, ms: U32, retries: U32, http: Hairpin.Client}# ---- JSONdef str(s: String) -> Json.Val: Json.Str{Json.utf8(s)}def kv(k: String, v: Json.Val) -> Bytes.Bytes & Json.Val: (Json.utf8(k), v)def num(+n: U32) -> Json.Val: Json.Num{Bytes.from_string(U32.show(n))}def obj(kvs: List<&1, Bytes.Bytes & Json.Val>) -> Json.Val: Json.Obj{kvs}def when(on: Bool, x: Bytes.Bytes & Json.Val, xs: List<&1, Bytes.Bytes & Json.Val>) -> List<&1, Bytes.Bytes & Json.Val>: match on: case True{}: Con{x, xs} case False{}: xsdef role(r: Role) -> String: match r: case User{}: "user" case Assistant{}: "assistant"def msg(+r: String, t: String) -> Json.Val: obj([kv("role", str(r)), kv("content", str(t))])def msgs(xs: List<&2, Msg>) -> List<&1, Json.Val>: match xs: case Nil{}: Nil{} case Con{Msg{r, t}, rest}: Con{msg(role(r), t), msgs(rest)}def sys(on: Bool, s: String, xs: List<&1, Json.Val>) -> List<&1, Json.Val>: match on: case True{}: Con{msg("system", s), xs} case False{}: xs# The request body for api. stream asks for SSE.def body(api: Api, req: Req, stream: Bool) -> Json.Val: match api: case Anthropic{}: Req{model, +system, ms, max} = req obj(Con{kv("model", str(model)), Con{kv("max_tokens", num(max)), when(Bool.not(String.is_empty(system)), kv("system", str(system)), Con{kv("messages", Json.Arr{msgs(ms)}), when(stream, kv("stream", Json.Flag{True{}}), Nil{})})}}) case OpenAI{}: Req{model, +system, ms, max} = req obj(Con{kv("model", str(model)), Con{kv("max_completion_tokens", num(max)), Con{kv("messages", Json.Arr{sys(Bool.not(String.is_empty(system)), system, msgs(ms))}), when(stream, kv("stream", Json.Flag{True{}}), Nil{})}}})# A JSON leaf: its path, as "content.0.text", and its text.type Leaf is Data: Leaf{p: String, v: String}def path(+p: String, +k: String) -> String: Bool.pick(String, String.is_empty(p), k, p ++ "." ++ k)def push.arr(xs: List<&1, Json.Val>, +p: String, +i: U32, t: List<&1, String & Json.Val>) -> List<&1, String & Json.Val>: match xs: case Nil{}: t case Con{x, rest}: Con{(path(p, U32.show(i)), x), push.arr(rest, p, (i + 1 : U32), t)}def push.obj(kvs: List<&1, Bytes.Bytes & Json.Val>, +p: String, t: List<&1, String & Json.Val>) -> List<&1, String & Json.Val>: match kvs: case Nil{}: t case Con{(k, x), rest}: Con{(path(p, Enc.utf8.decode(k)), x), push.obj(rest, p, t)}# The leaves under the stack's values, last first. f: at least the values left.def flat(f: Nat, stack: List<&1, String & Json.Val>, acc: List<&2, Leaf>) -> List<&2, Leaf>: match f: case 0n: acc case 1n+g: match stack: case Nil{}: acc case Con{(p, v), t}: match v: case Json.Null{}: flat(g, t, acc) case Json.Flag{on}: flat(g, t, Con{Leaf{p, Bool.pick(String, on, "true", "false")}, acc}) case Json.Num{s}: flat(g, t, Con{Leaf{p, Bytes.to_string(s)}, acc}) case Json.Str{s}: flat(g, t, Con{Leaf{p, Enc.utf8.decode(s)}, acc}) case Json.Arr{xs}: flat(g, push.arr(xs, p, 0, t), acc) case Json.Obj{kvs}: flat(g, push.obj(kvs, p, t), acc)def doc.of(+n: U32, m: Maybe<&1, Json.Val>) -> Maybe<&2, List<&2, Leaf>>: match m: case None{}: None{} case Some{v}: Some{List.reverse(&2, Leaf, flat(Nat.add(U32.to_nat(n), 1n), [("", v)], Nil{}))}# Every non-null leaf of a JSON text in document order, keyed by its path, as ("content.0.text", "Hi").# Strings are decoded; numbers keep their text. None when b is not JSON. Each value takes a byte, so n + 1 steps suffice.def doc(b: Bytes.Bytes) -> Maybe<&2, List<&2, Leaf>>: Bytes.Bytes{+n, buf} = b doc.of(n, Json.parse.bytes(Bytes.Bytes{n, buf}))# The first value at path k, or "".def look(d: List<&2, Leaf>, +k: String) -> String: match d: case Nil{}: "" case Con{Leaf{p, v}, t}: Bool.pick(String, String.eq(p, k), v, look(t, k))def count(s: String) -> U32: Maybe.default(&2, U32, Json.u32.num(s), 0)def dots(s: String, +n: U32) -> U32: match s: case SNil{}: n case SCon{Chr{+c}, t}: dots(t, Bool.pick(U32, U32.is_eq(c, 46), (n + 1 : U32), n))# Is p the text of a content block, "content.<i>.text"?def block(+p: String) -> Bool: Bool.and(Bool.and(String.starts_with(p, "content."), String.ends_with(p, ".text")), U32.is_eq(dots(p, 0), 2))# The text blocks of an Anthropic message, joined.def blocks(d: List<&2, Leaf>) -> String: match d: case Nil{}: "" case Con{Leaf{+p, v}, t}: Bool.pick(String, block(p), v, "") ++ blocks(t)def reply.of(api: Api, +d: List<&2, Leaf>) -> Reply: match api: case Anthropic{}: Reply{look(d, "id"), look(d, "model"), blocks(d), look(d, "stop_reason"), count(look(d, "usage.input_tokens")), count(look(d, "usage.output_tokens"))} case OpenAI{}: Reply{look(d, "id"), look(d, "model"), look(d, "choices.0.message.content"), look(d, "choices.0.finish_reason"), count(look(d, "usage.prompt_tokens")), count(look(d, "usage.completion_tokens"))}def reply.got(api: Api, b: Bytes.Bytes, m: Maybe<&2, List<&2, Leaf>>) -> Result<&1, &1, Err, Reply>: match m: case None{}: Fail{ErrReply{Enc.utf8.decode(b)}} case Some{d}: Done{reply.of(api, d)}def reply.copy(api: Api, r: Bytes.Bytes & Bytes.Bytes) -> Result<&1, &1, Err, Reply>: (b, c) = r reply.got(api, b, doc(c))# A 2xx response body as a Reply.def reply(api: Api, b: Bytes.Bytes) -> Result<&1, &1, Err, Reply>: reply.copy(api, Bytes.slice(b, 0, 4294967295))# ---- stream events# A text piece, the end, an error, or an event with no text.type Ev is Data: EText{s: String} EEnd{} EFail{e: Err} ESkip{}def ev.text(+s: String) -> Ev: Bool.pick(Ev, String.is_empty(s), ESkip{}, EText{s})def ev.doc(m: Maybe<&2, List<&2, Leaf>>) -> List<&2, Leaf>: Maybe.default(&2, List<&2, Leaf>, m, Nil{})def ev.anthropic(+name: String, data: Bytes.Bytes) -> Ev: +d = ev.doc(doc(data)) Bool.pick(Ev, String.eq(name, "content_block_delta"), ev.text(look(d, "delta.text")), Bool.pick(Ev, String.eq(name, "message_stop"), EEnd{}, Bool.pick(Ev, String.eq(name, "error"), EFail{ErrApi{200, look(d, "error.message")}}, ESkip{})))def ev.openai(+s: String) -> Ev: +d = ev.doc(doc(Bytes.from_string(s))) +why = look(d, "error.message") Bool.pick(Ev, String.eq(s, "[DONE]"), EEnd{}, Bool.pick(Ev, String.is_empty(why), ev.text(look(d, "choices.0.delta.content")), EFail{ErrApi{200, why}}))# What one SSE event of api means.def ev(api: Api, e: Sse.Message) -> Ev: match api: case Anthropic{}: Sse.Message{name, data, id} = e ev.anthropic(name, data) case OpenAI{}: Sse.Message{name, data, id} = e ev.openai(Bytes.to_string(data))# ---- requestsdef ok(+s: U32) -> Bool: Bool.and(U32.is_le(200, s), U32.is_lt(s, 300))# Statuses a later try may clear: 408, 409, 429, and 5xx, which holds Anthropic's 529.def again.status(+s: U32) -> Bool: Bool.or(Bool.or(U32.is_eq(s, 408), U32.is_eq(s, 409)), Bool.or(U32.is_eq(s, 429), U32.is_le(500, s)))# A refused connect or a timeout may clear.def again.err(+e: Http.Err) -> Maybe<&2, String>: match e: case Http.ErrConnect{code, why}: Some{""} case Http.ErrTimeout{}: Some{""} case other: None{}def again.of(+status: U32, +h: Map<&2, List<&2, String>>) -> Maybe<&2, String>: Bool.pick(Maybe<&2, String>, again.status(status), Some{Http.header(h, "retry-after")}, None{})# The result, with Some{Retry-After} when another try may help. Hairpin's judge for every call.def again(r: Result<&1, &1, Http.Err, Http.Res>) -> Result<&1, &1, Http.Err, Http.Res> & Maybe<&2, String>: match r: case Fail{+e}: (Fail{e}, again.err(e)) case Done{res}: Http.Res{+status, +h, b} = res (Done{Http.Res{status, h, b}}, again.of(status, h))def body.ok(good: Bool, +status: U32, b: Bytes.Bytes) -> Result<&1, &1, Err, Bytes.Bytes>: match good: case True{}: Done{b} case False{}: Fail{ErrApi{status, Enc.utf8.decode(b)}}# The 2xx body, or why there is none.def body.of(r: Result<&1, &1, Hairpin.Err, Http.Res>) -> Result<&1, &1, Err, Bytes.Bytes>: match r: case Fail{e}: Fail{ErrNet{e}} case Done{res}: Http.Res{+status, h, b} = res body.ok(ok(status), status, b)def url(api: Api, +base: String) -> String: match api: case Anthropic{}: base ++ "/v1/messages" case OpenAI{}: base ++ "/chat/completions"# ---- the clientdef new(+api: Api, base: String, headers: Map<&2, List<&2, String>>) -> Client: Client{api, base, headers, 600000, 2, Hairpin.timeout(Hairpin.new(), 600000)}def json(h: Map<&2, List<&2, String>>) -> Map<&2, List<&2, String>>: Http.set(h, "content-type", "application/json")# base https://api.anthropic.com, 10 min steps, 2 retries.def anthropic(key: String) -> Client: new(Anthropic{}, "https://api.anthropic.com", json(Http.set(Http.set(Http.empty(), "x-api-key", key), "anthropic-version", "2023-06-01")))# base https://api.openai.com/v1, 10 min steps, 2 retries.def openai(key: String) -> Client: new(OpenAI{}, "https://api.openai.com/v1", json(Http.set(Http.empty(), "authorization", "Bearer " ++ key)))# Another base URL, as for a provider that serves the same API.def base(c: Client, url: String) -> Client: Client{api, old, h, ms, n, http} = c Client{api, url, h, ms, n, http}# A header on every request, as anthropic-beta. It replaces one of the same name.def header(c: Client, k: String, v: String) -> Client: Client{api, b, h, ms, n, http} = c Client{api, b, Http.set(h, String.to_lower(k), v), ms, n, http}def timeout(c: Client, +ms: U32) -> Client: Client{api, b, h, old, n, http} = c Client{api, b, h, ms, n, Hairpin.timeout(http, ms)}def retry(c: Client, n: U32) -> Client: Client{api, b, h, ms, old, http} = c Client{api, b, h, ms, n, http}def close(c: Client) -> IO(Unit): Client{api, b, h, ms, n, http} = c Hairpin.close(http)def call.done(+api: Api, base: String, headers: Map<&2, List<&2, String>>, +ms: U32, +n: U32, x: Hairpin.Client & Retry.Budget & Result<&1, &1, Hairpin.Err, Http.Res>) -> Client & Result<&1, &1, Err, Bytes.Bytes>: (h, b, r) = x (Client{api, base, headers, ms, n, h}, body.of(r))def call.budget(+api: Api, +base: String, +headers: Map<&2, List<&2, String>>, body: Bytes.Bytes, y: Hairpin.Client & Retry.Budget) -> IO(Hairpin.Client & Retry.Budget & Result<&1, &1, Hairpin.Err, Http.Res>): (h, b) = y do IO<Hairpin.Client & Retry.Budget & Result<&1, &1, Hairpin.Err, Http.Res>>: enc : String <- Http.codings() Hairpin.request.as(~again, h, b, True{}, enc, "POST", url(api, base), headers, body)# POST body to the API with n retries on a budget of n + 1; the 2xx body comes back.# These POSTs are safe to repeat, so Hairpin retries them as again judges.def call(c: Client, body: Bytes.Bytes) -> IO(Client & Result<&1, &1, Err, Bytes.Bytes>): Client{+api, +base, +headers, +ms, +n, h} = c do IO<Client & Result<&1, &1, Err, Bytes.Bytes>>: y : Hairpin.Client & Retry.Budget <- Hairpin.budget(Hairpin.retry(h, n)) x : Hairpin.Client & Retry.Budget & Result<&1, &1, Hairpin.Err, Http.Res> <- call.budget(api, base, headers, body, y) return call.done(api, base, headers, ms, n, x)def raw.got(b: Bytes.Bytes, m: Maybe<&1, Json.Val>) -> Result<&1, &1, Err, Json.Val>: match m: case None{}: Fail{ErrReply{Enc.utf8.decode(b)}} case Some{v}: Done{v}def raw.copy(r: Bytes.Bytes & Bytes.Bytes) -> Result<&1, &1, Err, Json.Val>: (b, c) = r raw.got(b, Json.parse.bytes(c))def raw.of(r: Result<&1, &1, Err, Bytes.Bytes>) -> Result<&1, &1, Err, Json.Val>: match r: case Fail{e}: Fail{e} case Done{b}: raw.copy(Bytes.slice(b, 0, 4294967295))def raw.done(x: Client & Result<&1, &1, Err, Bytes.Bytes>) -> Client & Result<&1, &1, Err, Json.Val>: (c, r) = x (c, raw.of(r))# Any request body, as for tools or images, and the reply as JSON.def send.raw(c: Client, v: Json.Val) -> IO(Client & Result<&1, &1, Err, Json.Val>): do IO<Client & Result<&1, &1, Err, Json.Val>>: x : Client & Result<&1, &1, Err, Bytes.Bytes> <- call(c, Json.encode.bytes(v)) return raw.done(x)def send.of(r: Result<&1, &1, Err, Bytes.Bytes>, +api: Api) -> Result<&1, &1, Err, Reply>: match r: case Fail{e}: Fail{e} case Done{b}: reply(api, b)def send.done(+api: Api, x: Client & Result<&1, &1, Err, Bytes.Bytes>) -> Client & Result<&1, &1, Err, Reply>: (c, r) = x (c, send.of(r, api))# One whole reply.def send(c: Client, req: Req) -> IO(Client & Result<&1, &1, Err, Reply>): Client{+api, b, h, ms, n, http} = c do IO<Client & Result<&1, &1, Err, Reply>>: x : Client & Result<&1, &1, Err, Bytes.Bytes> <- call(Client{api, b, h, ms, n, http}, Json.encode.bytes(body(api, req, False{}))) return send.done(api, x)# ---- streamstype Stream is Type: Stream{api: Api, h: Http.Stream, rd: Sse.Reader}def open.res(x: Http.Stream & Http.Res) -> Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>: (st, res) = x Http.Res{+status, +h, b} = res (Done{st}, again.of(status, h))def open.judge(r: Result<&1, &1, Http.Err, Http.Stream>) -> Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>: match r: case Fail{+e}: (Fail{e}, again.err(e)) case Done{st}: open.res(Http.stream.res(st))def open.kept(body: Bytes.Bytes, j: Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>) -> Bytes.Bytes & Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>: (r, m) = j (body, r, m)def open.once(+url: String, +headers: Map<&2, List<&2, String>>, +ms: U32, r: Bytes.Bytes & Bytes.Bytes) -> IO(Bytes.Bytes & Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>): (body, spare) = r do IO<Bytes.Bytes & Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>>: s : Result<&1, &1, Http.Err, Http.Stream> <- Http.open.with("POST", url, headers, spare, ms) return open.kept(body, open.judge(s))def open.drop(r: Result<&1, &1, Http.Err, Http.Stream>) -> IO(Unit): match r: case Fail{e}: IO.pure(Unit, Unit{}) case Done{st}: Http.stream.close(st)# A refused stream closes before the next try.def open.go(left: Nat, +n: Nat, +url: String, +headers: Map<&2, List<&2, String>>, +ms: U32, t: Bytes.Bytes & Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>) -> IO(Result<&1, &1, Http.Err, Http.Stream>): match left: case 0n: (body, r, m) = t IO.pure(Result<&1, &1, Http.Err, Http.Stream>, r) case 1n+rest: (body, r, m) = t match m: case None{}: IO.pure(Result<&1, &1, Http.Err, Http.Stream>, r) case Some{v}: do IO<Result<&1, &1, Http.Err, Http.Stream>>: open.drop(r) Http.retry.sleep(v, n) tried : Bytes.Bytes & Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String> <- open.once(url, headers, ms, Bytes.slice(body, 0, 4294967295)) open.go(rest, 1n+n, url, headers, ms, tried)# A refused stream's error body, at most f more pieces, then the stream closed.def drain(f: Nat, x: Http.Stream & Result<&1, &1, Http.Err, Maybe<&1, Bytes.Bytes>>, acc: Bytes.Bytes) -> IO(Bytes.Bytes): match f: case 0n: (h, r) = x do IO<Bytes.Bytes>: Http.stream.close(h) return acc case 1n+g: (h, r) = x match r: case Fail{e}: do IO<Bytes.Bytes>: Http.stream.close(h) return acc case Done{m}: match m: case None{}: do IO<Bytes.Bytes>: Http.stream.close(h) return acc case Some{b}: do IO<Bytes.Bytes>: y : Http.Stream & Result<&1, &1, Http.Err, Maybe<&1, Bytes.Bytes>> <- Http.stream.read(h) drain(g, y, Bytes.append(acc, b))def start.refused(+status: U32, h: Http.Stream) -> IO(Result<&1, &1, Err, Http.Stream>): do IO<Result<&1, &1, Err, Http.Stream>>: y : Http.Stream & Result<&1, &1, Http.Err, Maybe<&1, Bytes.Bytes>> <- Http.stream.read(h) b : Bytes.Bytes <- drain(64n, y, Bytes.new(0)) return Fail{ErrApi{status, Enc.utf8.decode(b)}}def start.ok(good: Bool, +status: U32, h: Http.Stream) -> IO(Result<&1, &1, Err, Http.Stream>): match good: case True{}: IO.pure(Result<&1, &1, Err, Http.Stream>, Done{h}) case False{}: start.refused(status, h)def start.res(x: Http.Stream & Http.Res) -> IO(Result<&1, &1, Err, Http.Stream>): (h, res) = x Http.Res{+status, hd, b} = res start.ok(ok(status), status, h)def start(r: Result<&1, &1, Http.Err, Http.Stream>) -> IO(Result<&1, &1, Err, Http.Stream>): match r: case Fail{e}: IO.pure(Result<&1, &1, Err, Http.Stream>, Fail{ErrNet{Hairpin.ErrHttp{e}}}) case Done{h}: start.res(Http.stream.res(h))def stream.of(r: Result<&1, &1, Err, Http.Stream>, +api: Api) -> Result<&1, &1, Err, Stream>: match r: case Fail{e}: Fail{e} case Done{h}: Done{Stream{api, h, Sse.reader()}}# Any request body that asks for SSE, as for tools. A stream opens its own connection, outside the pool.def stream.raw(c: Client, v: Json.Val) -> IO(Client & Result<&1, &1, Err, Stream>): Client{+api, +base, +headers, +ms, +n, h} = c do IO<Client & Result<&1, &1, Err, Stream>>: first : Bytes.Bytes & Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String> <- open.once(url(api, base), headers, ms, Bytes.slice(Json.encode.bytes(v), 0, 4294967295)) r : Result<&1, &1, Http.Err, Http.Stream> <- open.go(U32.to_nat(n), 0n, url(api, base), headers, ms, first) s : Result<&1, &1, Err, Http.Stream> <- start(r) return (Client{api, base, headers, ms, n, h}, stream.of(s, api))# The reply as it is written: read it with next.def stream(c: Client, req: Req) -> IO(Client & Result<&1, &1, Err, Stream>): Client{+api, b, h, ms, n, http} = c stream.raw(Client{api, b, h, ms, n, http}, body(api, req, True{}))def stream.close(s: Stream) -> IO(Unit): Stream{api, h, rd} = s Http.stream.close(h)# The reader after the next event, or the stream's result.type Rn is Type: RnNext{h: Http.Stream, r: Sse.Reader & Sse.Next} RnOut{h: Http.Stream, rd: Sse.Reader, r: Result<&1, &1, Err, Maybe<&1, Sse.Message>>}def event.read(rd: Sse.Reader, x: Http.Stream & Result<&1, &1, Http.Err, Maybe<&1, Bytes.Bytes>>) -> Rn: (h, r) = x match r: case Fail{e}: RnOut{h, rd, Fail{ErrNet{Hairpin.ErrHttp{e}}}} case Done{m}: match m: case None{}: RnOut{h, rd, Done{None{}}} case Some{b}: RnNext{h, Sse.next(Sse.feed(rd, b))}# f: pieces left to read before the stream counts as stalled.def event.loop(f: Nat, st: Rn) -> IO(Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>>): match f: case 0n: match st: case RnNext{h, r}: (rd, n) = r IO.pure(Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>>, (h, rd, Fail{ErrReply{"too many pieces without an event"}})) case RnOut{h, rd, r}: IO.pure(Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>>, (h, rd, r)) case 1n+g: match st: case RnNext{h, r}: (rd, n) = r match n: case Sse.Got{e}: IO.pure(Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>>, (h, rd, Done{Some{e}})) case Sse.Want{}: do IO<Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>>>: x : Http.Stream & Result<&1, &1, Http.Err, Maybe<&1, Bytes.Bytes>> <- Http.stream.read(h) event.loop(g, event.read(rd, x)) case RnOut{h, rd, r}: IO.pure(Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>>, (h, rd, r))def event.done(+api: Api, x: Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>>) -> Stream & Result<&1, &1, Err, Maybe<&1, Sse.Message>>: (h, rd, r) = x (Stream{api, h, rd}, r)# The next SSE event, or None when the stream ends. An event the end cuts off is dropped.def event(s: Stream) -> IO(Stream & Result<&1, &1, Err, Maybe<&1, Sse.Message>>): Stream{+api, h, rd} = s do IO<Stream & Result<&1, &1, Err, Maybe<&1, Sse.Message>>>: x : Http.Stream & Sse.Reader & Result<&1, &1, Err, Maybe<&1, Sse.Message>> <- event.loop(Nat.mul(65536n, 256n), RnNext{h, Sse.next(rd)}) return event.done(api, x)def next.ev(r: Result<&1, &1, Err, Maybe<&1, Sse.Message>>, +api: Api) -> Ev: match r: case Fail{e}: EFail{e} case Done{m}: match m: case None{}: EEnd{} case Some{e}: ev(api, e)def next.of(x: Stream & Result<&1, &1, Err, Maybe<&1, Sse.Message>>) -> Stream & Ev: (s, r) = x Stream{+api, h, rd} = s (Stream{api, h, rd}, next.ev(r, api))# f: events left to skip.def next.loop(f: Nat, x: Stream & Ev) -> IO(Stream & Result<&1, &1, Err, Maybe<&2, String>>): match f: case 0n: (s, e) = x IO.pure(Stream & Result<&1, &1, Err, Maybe<&2, String>>, (s, Fail{ErrReply{"too many events without text"}})) case 1n+g: (s, e) = x match e: case EText{t}: IO.pure(Stream & Result<&1, &1, Err, Maybe<&2, String>>, (s, Done{Some{t}})) case EEnd{}: IO.pure(Stream & Result<&1, &1, Err, Maybe<&2, String>>, (s, Done{None{}})) case EFail{err}: IO.pure(Stream & Result<&1, &1, Err, Maybe<&2, String>>, (s, Fail{err})) case ESkip{}: do IO<Stream & Result<&1, &1, Err, Maybe<&2, String>>>: y : Stream & Result<&1, &1, Err, Maybe<&1, Sse.Message>> <- event(s) next.loop(g, next.of(y))# The next piece of reply text, or None at the end.def next(s: Stream) -> IO(Stream & Result<&1, &1, Err, Maybe<&2, String>>): do IO<Stream & Result<&1, &1, Err, Maybe<&2, String>>>: y : Stream & Result<&1, &1, Err, Maybe<&1, Sse.Message>> <- event(s) next.loop(Nat.mul(65536n, 256n), next.of(y))