Experiments for playing with atproto in Gleam.
:construction: Initial go at an NSID parser.
Hayleigh Thompson
(Jul 15, 2026, 10:42 PM +0200)
c48abf3d
52c75380
+320
+234
src/at/nsid.gleam
+234
src/at/nsid.gleam
···
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// IMPORTS ---------------------------------------------------------------------
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import gleam/list
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import gleam/string
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// TYPES -----------------------------------------------------------------------
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///
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///
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pub opaque type Nsid {
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Nsid(authority: List(String), name: String)
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}
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// CONSTRUCTORS ----------------------------------------------------------------
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///
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///
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pub fn from_string(input: String) -> Result(Nsid, Nil) {
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do_from_string(input, input, 0, 0, [], 0, 0)
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}
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fn do_from_string(
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input: String,
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remaining: String,
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//
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slice_offset: Int,
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slice_length: Int,
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//
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authority_segments: List(String),
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authority_count: Int,
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authority_length: Int,
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) -> Result(Nsid, Nil) {
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case remaining {
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// An NSID must have at least three segments, so at least two authority
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// segments and the name segment.
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//
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// The entire authority part must not exceed 253 characters, *including*
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// the dot separators between segments.
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//
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// The name segment must be at least 1 character long and no more than 63
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// characters.
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//
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// The entire NSID must not exceed 317 characters, but we don't need to
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// check this explicitly because the previous two checks already guarantee
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// this.
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""
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if authority_count < 2
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|| authority_length > 253
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|| slice_length < 1
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|| slice_length > 63
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-> Error(Nil)
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"" ->
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// The name segment must not start with a digit.
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case string.slice(input, slice_offset, slice_length) {
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"1" <> _
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| "2" <> _
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| "3" <> _
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| "4" <> _
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| "5" <> _
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| "6" <> _
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| "7" <> _
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| "8" <> _
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| "9" <> _ -> Error(Nil)
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name ->
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// The name segment must not contain a hyphen.
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case string.contains(name, "-") {
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True -> Error(Nil)
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False ->
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Ok(Nsid(authority: list.reverse(authority_segments), name:))
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}
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}
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// Each segment must be at least 1 character long and no more than 63 characters.
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"." <> _ if slice_length < 1 || slice_length > 63 -> Error(Nil)
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"." <> remaining if authority_length == 0 -> {
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let slice =
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input
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|> string.slice(slice_offset, slice_length)
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|> string.lowercase
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let slice_length = slice_length + 1
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do_from_string(
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input,
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remaining,
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slice_length,
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0,
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[slice],
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1,
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slice_length,
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)
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}
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"." <> remaining -> {
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let slice =
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input
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|> string.slice(slice_offset, slice_length)
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|> string.lowercase
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let slice_length = slice_length + 1
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do_from_string(
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input,
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remaining,
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slice_offset + slice_length,
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0,
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[slice, ..authority_segments],
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authority_count + 1,
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authority_length + slice_length,
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)
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}
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// An authority segment cannot start or end with a hyphen.
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"-." <> _ -> Error(Nil)
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"-" if slice_length == 0 -> Error(Nil)
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// The first authority segment cannot start with a digit.
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"0" <> _
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| "1" <> _
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| "2" <> _
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| "3" <> _
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| "4" <> _
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| "5" <> _
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| "6" <> _
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| "7" <> _
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| "8" <> _
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| "9" <> _
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if slice_length == 0 && authority_length == 0
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-> Error(Nil)
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"-" <> remaining
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| // [0-9]
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"0" <> remaining
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| "1" <> remaining
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| "2" <> remaining
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| "3" <> remaining
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| "4" <> remaining
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| "5" <> remaining
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| "6" <> remaining
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| "7" <> remaining
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| "8" <> remaining
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| "9" <> remaining
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| // [a-z]
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"a" <> remaining
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| "b" <> remaining
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| "c" <> remaining
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| "d" <> remaining
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| "e" <> remaining
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| "f" <> remaining
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| "h" <> remaining
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| "g" <> remaining
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| "i" <> remaining
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| "j" <> remaining
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| "k" <> remaining
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| "l" <> remaining
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| "m" <> remaining
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| "n" <> remaining
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| "o" <> remaining
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| "p" <> remaining
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| "q" <> remaining
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| "r" <> remaining
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| "s" <> remaining
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| "t" <> remaining
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| "u" <> remaining
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| "v" <> remaining
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| "w" <> remaining
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| "x" <> remaining
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| "y" <> remaining
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| "z" <> remaining
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| // [A-Z]
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"A" <> remaining
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| "B" <> remaining
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| "C" <> remaining
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| "D" <> remaining
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| "E" <> remaining
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| "F" <> remaining
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| "G" <> remaining
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| "H" <> remaining
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| "I" <> remaining
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| "J" <> remaining
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| "K" <> remaining
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| "L" <> remaining
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| "M" <> remaining
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| "N" <> remaining
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| "O" <> remaining
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| "P" <> remaining
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| "Q" <> remaining
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| "R" <> remaining
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| "S" <> remaining
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| "T" <> remaining
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| "U" <> remaining
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| "V" <> remaining
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| "Y" <> remaining
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| "W" <> remaining
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| "X" <> remaining
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| "Z" <> remaining ->
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do_from_string(
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input,
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remaining,
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slice_offset,
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slice_length + 1,
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authority_segments,
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authority_count,
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authority_length,
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)
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_ -> Error(Nil)
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}
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}
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// QUERIES ---------------------------------------------------------------------
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///
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///
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pub fn authority(nsid: Nsid) -> List(String) {
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nsid.authority
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}
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///
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///
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pub fn name(nsid: Nsid) -> String {
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nsid.name
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}
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// CONVERSIONS -----------------------------------------------------------------
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///
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///
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pub fn to_string(nsid: Nsid) -> String {
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use out, segment <- list.fold_right(nsid.authority, nsid.name)
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segment <> "." <> out
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}
+86
test/at/nsid_test.gleam
+86
test/at/nsid_test.gleam
···
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// IMPORTS ---------------------------------------------------------------------
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import at/nsid
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import gleam/list
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// FIXTURES --------------------------------------------------------------------
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const valid = [
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"com.ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo.foo",
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"com.example.ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo",
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//
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// There's currently an open issue on the atproto interop repo about this test
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// case, as it does not currently respect the 253 character limit for the authority
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// part: https://github.com/bluesky-social/atproto-interop-tests/issues/15
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//
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// "com.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.foo",
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//
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"com.example.fooBar",
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"com.example.fooBarV2",
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"net.users.bob.ping",
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"a.b.c",
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"m.xn--masekowski-d0b.pl",
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"one.two.three",
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"one.two.three.four-and.FiVe",
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"one.2.three",
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"a-0.b-1.c",
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"a0.b1.cc",
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"cn.8.lex.stuff",
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"test.12345.record",
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"a01.thing.record",
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"a.0.c",
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"xn--fiqs8s.xn--fiqa61au8b7zsevnm8ak20mc4a87e.record.two",
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"a0.b1.c3",
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"com.example.f00",
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"onion.expyuzz4wqqyqhjn.spec.getThing",
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"onion.g2zyxa5ihm7nsggfxnu52rck2vv4rvmdlkiu3zzui5du4xyclen53wid.lex.deleteThing",
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"org.4chan.lex.getThing",
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"cn.8.lex.stuff",
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"onion.2gzyxa5ihm7nsggfxnu52rck2vv4rvmdlkiu3zzui5du4xyclen53wid.lex.deleteThing",
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]
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const invalid = [
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"com.oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo.foo",
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"com.example.oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo",
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"com.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.middle.foo",
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"com.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.x",
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"com.example.foo.*",
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"com.example.foo.blah*",
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"com.example.foo.*blah",
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"com.exa💩ple.thing",
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"a-0.b-1.c-3",
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"a-0.b-1.c-o",
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"1.0.0.127.record",
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"0two.example.foo",
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"example.com",
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"com.example",
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"a.",
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".one.two.three",
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"one.two.three ",
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"one.two..three",
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"one .two.three",
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" one.two.three",
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"com.exa💩ple.thing",
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"com.atproto.feed.p@st",
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"com.atproto.feed.p_st",
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"com.atproto.feed.p*st",
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"com.atproto.feed.po#t",
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"com.atproto.feed.p!ot",
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"com.example-.foo",
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"com.example.fooBar.2",
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]
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// TESTS -----------------------------------------------------------------------
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pub fn atproto_interop_valid_nsid_test() {
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use input <- list.each(valid)
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let assert Ok(nsid) = nsid.from_string(input) as input
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assert nsid.to_string(nsid) == input
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}
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pub fn atproto_interop_invalid_nsid_test() {
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use input <- list.each(invalid)
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assert nsid.from_string(input) == Error(Nil) as input
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}