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Codex re-review of the fix commit confirmed both prior findings resolved and raised one new Medium: RFC 7232 would 412 (not 400) a syntactically-valid but non-matching If-Match (non-canonical "03", weak W/"3", tag lists, empty, overflow). Deferred to #197 (cold contract pass) as #265 — fail-safe today (the mutation is rejected, never applied) and no first-party client is affected. Records the deferral where the #253 fan-out will copy the parser: a code comment in ConcurrencyHeaders + a note in api-conventions §7a. Refs #253 #265 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
78 lines
3.4 KiB
C#
78 lines
3.4 KiB
C#
using System.Globalization;
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using LanguageExt;
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using Microsoft.AspNetCore.Http;
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using Microsoft.Extensions.Primitives;
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namespace ErsatzTV.Extensions;
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/// <summary>Classification of a request's <c>If-Match</c> header for the #253 concurrency contract.</summary>
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public enum IfMatchKind
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{
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/// <summary>No <c>If-Match</c> header — Phase 1 force-write (Phase 2 will make this a 428).</summary>
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Absent,
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/// <summary><c>If-Match: *</c> — the scripted force-write escape hatch; skip the version check.</summary>
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Any,
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/// <summary>A strong entity-tag of a decimal aggregate version, e.g. <c>"3"</c>.</summary>
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Version,
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/// <summary>An unparseable value — the controller returns 400.</summary>
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Malformed
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}
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public readonly record struct IfMatchCondition(IfMatchKind Kind, int Version)
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{
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/// <summary>The version to check against, or <c>None</c> for absent/wildcard (force-write).</summary>
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public Option<int> ExpectedVersion => Kind == IfMatchKind.Version ? Version : Option<int>.None;
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}
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/// <summary>
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/// Parse/emit the optimistic-concurrency HTTP headers (issue #253). GET responses carry a strong
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/// <c>ETag</c> of the aggregate's integer <c>Version</c>; PUT requests carry the last-seen version
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/// in <c>If-Match</c>. See <c>docs/api-conventions.md</c> §7a.
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/// </summary>
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public static class ConcurrencyHeaders
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{
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public static IfMatchCondition ParseIfMatch(HttpRequest request)
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{
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StringValues raw = request.Headers.IfMatch;
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if (StringValues.IsNullOrEmpty(raw))
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{
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return new IfMatchCondition(IfMatchKind.Absent, 0);
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}
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string value = raw.ToString().Trim();
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if (value == "*")
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{
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return new IfMatchCondition(IfMatchKind.Any, 0);
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}
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// Strong entity-tag of a decimal version, e.g. "3". Weak tags (W/"…") are not honored:
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// this contract's ETags are always strong. An ETag is an opaque token, so only the exact
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// canonical form we emit is accepted — a non-negative decimal with no sign, surrounding
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// whitespace, or leading zeros (`NumberStyles.None` + the leading-zero guard reject "+3",
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// " 3 ", and "03", which must NOT be treated as equal to the emitted "3").
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if (value.Length >= 2 && value[0] == '"' && value[^1] == '"')
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{
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string inner = value[1..^1];
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if (inner.Length > 0 && (inner.Length == 1 || inner[0] != '0') &&
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int.TryParse(inner, NumberStyles.None, CultureInfo.InvariantCulture, out int version))
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{
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return new IfMatchCondition(IfMatchKind.Version, version);
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}
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}
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// Everything else (a valid-but-non-canonical strong tag like "03", a weak tag W/"3", an
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// entity-tag list, or plain garbage) is treated as Malformed → 400. Strictly, RFC 7232 would
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// 412 a syntactically-valid tag that merely doesn't strong-match; that refinement (plus
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// weak-tag comparison, list support, and 412-vs-404 ordering) is deferred to the #197 cold
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// contract pass — see #265. This is fail-safe (the mutation is rejected, never applied) and the
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// first-party SPA only ever echoes the single canonical tag we emit.
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return new IfMatchCondition(IfMatchKind.Malformed, 0);
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}
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public static void SetETag(HttpResponse response, int version) =>
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response.Headers.ETag = $"\"{version}\"";
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}
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