middleware

Built-in middleware functions. All follow the fn(Conn(body), fn(Conn(body)) -> Response) -> Response signature.

Types

pub type CorsOptions {
  CorsOptions(
    allow_origins: List(String),
    allow_methods: List(String),
    allow_headers: List(String),
    max_age_seconds: Option(Int),
  )
}

Functions

log

pub fn log(c: Conn(Connection), next: fn(Conn(Connection)) -> Response(ResponseData)) -> Response(ResponseData)

Logs method, path, status code, and duration using the logging library.

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request_id

pub fn request_id(c: Conn(body), next: fn(Conn(body)) -> Response(ResponseData)) -> Response(ResponseData)

Reads X-Request-Id from the incoming request; generates a UUID v4 if absent. Sets X-Request-Id on the response.

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cors

pub fn cors(opts: CorsOptions, c: Conn(body), next: fn(Conn(body)) -> Response(ResponseData)) -> Response(ResponseData)

Adds CORS headers based on opts. Handles OPTIONS preflight requests with a 204 response.

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cors_allow_all

pub fn cors_allow_all() -> CorsOptions

Returns permissive CorsOptions with * origin and common methods. Useful for development.

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static_files

pub fn static_files(under prefix: String, from dir: String) -> Middleware(Connection)

Serves files from dir on disk under the given URL prefix.

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body_limit

pub fn body_limit(limit_bytes: Int) -> Middleware(Connection)

Reads and buffers the full request body, rejecting requests larger than limit_bytes with 413. Converts Conn(Connection) to Conn(BitArray) for downstream handlers.

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Request body helpers (in mistweaver/request)

These live in mistweaver/request and require the body to have been buffered first by body_limit.

json_body

pub fn json_body(req: Request(BitArray), using decoder: decode.Decoder(a)) -> Result(a, String)

Decode the request body as JSON using the given decoder. Returns Error if the body is not valid UTF-8, not valid JSON, or does not match the decoder.

form_params

pub fn form_params(req: Request(BitArray)) -> List(#(String, String))

Parse a URL-encoded (application/x-www-form-urlencoded) body into a key/value list.

form_param

pub fn form_param(params: List(#(String, String)), key: String) -> Option(String)

Look up a single field from a pre-parsed form params list.