feat(http/unstable): add radix tree router; keep linear scan as routeLinear

[esroyo]

Add routeRadix(), a radix tree router that provides O(segments) dispatch for static, parametric, and wildcard routes. Routes with complex URLPattern syntax (regex constraints, optional groups, inline wildcards, modifier suffixes) fall back to linear matching while preserving insertion order.

• routeRadix: radix tree with fallback to linear for complex patterns
• routeLinear: the original linear scan, extracted as its own export
• route: re-exported alias for routeLinear

The radix router matches routeLinear semantics exactly; insertion order is always respected, even when static and parametric routes overlap at the same tree depth.

Benchmarks show 1.5–9x improvement on static/parametric/wildcard routes, with negligible overhead on complex fallback patterns.

---

---
config:
    themeVariables:
        xyChart:
            plotColorPalette: "#e05c5c, #4a90d9"
---
xychart-beta
    title "route: 🔴 linear vs 🔵 radix - Avg latency (µs)"
    x-axis [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
    y-axis "Avg latency (µs)" 0 --> 7

    line [0.91, 2.04, 6.1, 1.63, 5.54, 1.49, 2.84, 1.08, 3.15, 0.9, 1.45, 1.98]
    line [1.08, 1.38, 1.39, 0.62, 0.61, 1.55, 1.66, 0.91, 1.73, 1.46, 1.62, 2.1]

Loading

#	Group	🔴 linear (µs)	🔵 radix (µs)
1	static route — first in small table	0.91	1.08
2	static route — last in small table	2.04	1.38
3	static route — last in large table	6.1	1.39
4	static route — miss (small table)	1.63	0.62
5	static route — miss (large table)	5.54	0.61
6	parametric route — single param	1.49	1.55
7	parametric route — two params (nested)	2.84	1.66
8	parametric route — method mismatch	1.08	0.91
9	wildcard route	3.15	1.73
10	complex — regex constraint	0.9	1.46
11	complex — optional group	1.45	1.62
12	complex — inline wildcard with suffix	1.98	2.1

---

    CPU | AMD Ryzen 7 PRO 6850U with Radeon Graphics
Runtime | Deno 2.7.9 (x86_64-unknown-linux-gnu)

file:///../denoland/std/http/unstable_route_bench.ts

| benchmark   | time/iter (avg) |        iter/s |      (min … max)      |      p75 |      p99 |     p995 |
| ----------- | --------------- | ------------- | --------------------- | -------- | -------- | -------- |

group static route — first in small table
| linear      |        921.1 ns |     1,086,000 | (869.7 ns …   1.4 µs) | 921.5 ns |   1.4 µs |   1.4 µs |
| radix       |          1.1 µs |       885,100 | (  1.1 µs …   1.3 µs) |   1.1 µs |   1.3 µs |   1.3 µs |

summary
  linear
     1.23x faster than radix

group static route — last in small table
| linear      |          2.0 µs |       494,200 | (  2.0 µs …   2.6 µs) |   2.0 µs |   2.6 µs |   2.6 µs |
| radix       |          1.3 µs |       751,200 | (  1.3 µs …   1.7 µs) |   1.3 µs |   1.7 µs |   1.7 µs |

summary
  linear
     1.52x slower than radix

group static route — last in large table
| linear      |          5.9 µs |       170,100 | (  5.8 µs …   6.1 µs) |   5.9 µs |   6.1 µs |   6.1 µs |
| radix       |          1.3 µs |       750,600 | (  1.3 µs …   1.6 µs) |   1.3 µs |   1.6 µs |   1.6 µs |

summary
  linear
     4.41x slower than radix

group static route — miss (small table)
| linear      |          1.7 µs |       596,400 | (  1.6 µs …   2.1 µs) |   1.7 µs |   2.1 µs |   2.1 µs |
| radix       |        622.6 ns |     1,606,000 | (600.0 ns … 702.4 ns) | 621.7 ns | 702.4 ns | 702.4 ns |

summary
  linear
     2.69x slower than radix

group static route — miss (large table)
| linear      |          5.6 µs |       179,100 | (  5.4 µs …   5.9 µs) |   5.6 µs |   5.9 µs |   5.9 µs |
| radix       |        606.1 ns |     1,650,000 | (594.0 ns … 641.1 ns) | 610.5 ns | 641.1 ns | 641.1 ns |

summary
  linear
     9.21x slower than radix

group parametric route — single param
| linear      |          1.5 µs |       645,600 | (  1.5 µs …   1.7 µs) |   1.6 µs |   1.7 µs |   1.7 µs |
| radix       |          1.5 µs |       649,500 | (  1.5 µs …   1.9 µs) |   1.5 µs |   1.9 µs |   1.9 µs |

summary
  linear
     1.01x slower than radix

group parametric route — two params (nested)
| linear      |          2.8 µs |       360,900 | (  2.7 µs …   2.9 µs) |   2.8 µs |   2.9 µs |   2.9 µs |
| radix       |          1.6 µs |       614,300 | (  1.6 µs …   1.7 µs) |   1.7 µs |   1.7 µs |   1.7 µs |

summary
  linear
     1.70x slower than radix

group parametric route — method mismatch
| linear      |          1.1 µs |       924,900 | (  1.0 µs …   1.4 µs) |   1.1 µs |   1.4 µs |   1.4 µs |
| radix       |        929.0 ns |     1,076,000 | (900.7 ns … 980.0 ns) | 933.5 ns | 980.0 ns | 980.0 ns |

summary
  linear
     1.16x slower than radix

group wildcard route
| linear      |          3.2 µs |       314,400 | (  3.1 µs …   3.6 µs) |   3.2 µs |   3.6 µs |   3.6 µs |
| radix       |          1.7 µs |       600,900 | (  1.6 µs …   2.0 µs) |   1.7 µs |   2.0 µs |   2.0 µs |

summary
  linear
     1.91x slower than radix

group complex — regex constraint
| linear      |        947.0 ns |     1,056,000 | (908.1 ns …   1.3 µs) | 947.5 ns |   1.3 µs |   1.3 µs |
| radix       |          1.5 µs |       673,300 | (  1.4 µs …   1.7 µs) |   1.5 µs |   1.7 µs |   1.7 µs |

summary
  linear
     1.57x faster than radix

group complex — optional group
| linear      |          1.5 µs |       680,000 | (  1.4 µs …   1.7 µs) |   1.5 µs |   1.7 µs |   1.7 µs |
| radix       |          1.6 µs |       625,800 | (  1.6 µs …   1.8 µs) |   1.6 µs |   1.8 µs |   1.8 µs |

summary
  linear
     1.09x faster than radix

group complex — inline wildcard with suffix
| linear      |          1.9 µs |       529,200 | (  1.8 µs …   2.1 µs) |   1.9 µs |   2.1 µs |   2.1 µs |
| radix       |          2.0 µs |       490,400 | (  2.0 µs …   2.2 µs) |   2.0 µs |   2.2 µs |   2.2 µs |

summary
  linear
     1.08x faster than radix

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[codecov]

Codecov Report

❌ Patch coverage is 93.67089% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.60%. Comparing base (cd03740) to head (632ecdc).

Files with missing lines	Patch %	Lines
http/unstable_route.ts	93.67%	7 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7075      +/-   ##
==========================================
- Coverage   94.61%   94.60%   -0.01%     
==========================================
  Files         634      634              
  Lines       51799    51942     +143     
  Branches     9329     9376      +47     
==========================================
+ Hits        49009    49141     +132     
- Misses       2216     2223       +7     
- Partials      574      578       +4     

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[esroyo]

@bartlomieju Thank you for the insightful comments! I mostly agree with your feedback (except the Array#sort comment perhaps) and have addressed all the points you raised. Thanks so much for your time ❤️

[esroyo]

[updated]

---
config:
    themeVariables:
        xyChart:
            plotColorPalette: "#e05c5c, #4a90d9"
---
xychart-beta
    title "AMD Ryzen 7 PRO 6850U — route benchmark"
    x-axis [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
    y-axis "Avg latency (µs)" 0 --> 6

    line [0.92, 1.96, 5.86, 1.63, 5.6, 1.53, 2.72, 1.06, 3.17, 0.93, 1.46, 1.89]
    line [1, 1.12, 1.07, 0.43, 0.43, 1.18, 1.31, 0.54, 1.39, 1.05, 1.44, 1.88]

Loading

🔴 linear    🔵 radix

#	Group	🔴 linear (µs)	🔵 radix (µs)
1	static route — first in small table	0.92	1
2	static route — last in small table	1.96	1.12
3	static route — last in large table	5.86	1.07
4	static route — miss (small table)	1.63	0.43
5	static route — miss (large table)	5.6	0.43
6	parametric route — single param	1.53	1.18
7	parametric route — two params (nested)	2.72	1.31
8	parametric route — method mismatch	1.06	0.54
9	wildcard route	3.17	1.39
10	complex — regex constraint	0.93	1.05
11	complex — optional group	1.46	1.44
12	complex — inline wildcard with suffix	1.89	1.88

[lunadogbot]

Bartlomieju's review points are addressed across four commits: route keeps linear-scan semantics (export { routeLinear as route }), per-request radixCandidates/sort replaced with minIndex subtree pruning in RouteNode, backslash escapes route through the linear fallback, parsePathname now documents the Request#url scoping, and the routeRadix JSDoc explicitly calls out that the tree is keyed by pathname only and other URLPattern constraints get validated by pattern.exec per request.

The walk's static→param→wildcard recursion order doesn't compromise "first registered wins": tryRoute rejects any candidate where r.index >= state.bestIndex, and the param route registered before static route preserves insertion order step at http/unstable_route_test.ts:438 exercises exactly that case. Running the full test harness against both routeRadix and routeLinear (lines 461-462) is the strongest behavioural parity signal.

• nit: Route's @linkcode route at http/unstable_route.ts:31 still names a single function. Route is shared by both routeRadix and routeLinear, so linking to one is still slightly misleading even with route aliasing routeLinear.

[lunadogbot]

@bartlomieju this is ready to merge