`nx_cms_a11y.nx` source

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1// nx_cms_a11y.nx -- CMS ACCESSIBILITY (WCAG) auditor (the wp-accessibility class, built honestly). Static
2// HTML checks against a focused, citable WCAG 2.x rule set -- the kind of automated a11y gate WordPress
3// themes routinely fail:
4//   R1 WCAG 3.1.1  : the document declares a language (<html ... lang=...>)
5//   R2 WCAG 1.1.1  : every <img> carries a non-empty alt= (text alternative)
6//   R3 WCAG 1.3.1  : heading levels are not SKIPPED (h1 -> h3 with no h2 = fail)
7//   R4 WCAG 4.1.2  : every non-hidden <input> has an accessible name (aria-label=)
8// Pure functions over an HTML buffer (defensive at the boundary, rule 12). license_tier: ORIGINAL
9// module: nishi-core.cms.a11y
10// depends: nishi-core.io.syscalls
11// capability: CMS
12import "nx_syscalls.nx"
13
14func a11_slen(s: *u8) -> i64 { var n: i64=0; while s[n]!=(0 as u8){n=n+1} return n }
15
16// first offset of NUL-terminated needle in buf[from..n); -1 if absent
17func a11_find(buf: *u8, from: i64, n: i64, needle: *u8) -> i64 {
18    let nl: i64 = a11_slen(needle)
19    var i: i64 = from
20    while i + nl <= n {
21        var q: i64 = 0
22        var ok: i64 = 1
23        while q < nl { if (buf[i+q] as i64) != (needle[q] as i64) { ok = 0; q = nl } q = q + 1 }
24        if ok == 1 { return i }
25        i = i + 1
26    }
27    return 0 - 1
28}
29
30// offset of the next '>' at or after `from` (tag end), or n
31func a11_tag_end(buf: *u8, from: i64, n: i64) -> i64 {
32    var i: i64 = from
33    while i < n { if (buf[i] as i64) == 62 { return i } i = i + 1 }
34    return n
35}
36
37// R1 WCAG 3.1.1: document declares a language. find "<html", require "lang=" before that tag closes.
38func a11y_has_lang(buf: *u8, n: i64) -> i64 {
39    let h: i64 = a11_find(buf, 0, n, "<html" as *u8)
40    if h < 0 { return 0 }
41    let te: i64 = a11_tag_end(buf, h, n)
42    if a11_find(buf, h, te, "lang=" as *u8) >= 0 { return 1 }
43    return 0
44}
45
46// helper: does the attribute attr (e.g. "alt=") appear with a NON-EMPTY quoted value inside [from,end)?
47func a11_attr_nonempty(buf: *u8, from: i64, end: i64, attr: *u8) -> i64 {
48    let a: i64 = a11_find(buf, from, end, attr)
49    if a < 0 { return 0 }
50    let al: i64 = a11_slen(attr)
51    let vq: i64 = a + al          // expected opening quote position
52    if vq + 1 >= end { return 0 }
53    if (buf[vq] as i64) != 34 { return 0 }     // must be a double-quote
54    if (buf[vq+1] as i64) == 34 { return 0 }   // empty value ("") -> fail
55    return 1
56}
57
58// R2 WCAG 1.1.1: every <img> has a non-empty alt=. returns 1 if all OK (or no imgs), 0 if any missing/empty.
59func a11y_imgs_alt(buf: *u8, n: i64) -> i64 {
60    var i: i64 = 0
61    while i >= 0 {
62        let p: i64 = a11_find(buf, i, n, "<img" as *u8)
63        if p < 0 { return 1 }
64        let te: i64 = a11_tag_end(buf, p, n)
65        if a11_attr_nonempty(buf, p, te, "alt=" as *u8) == 0 { return 0 }
66        i = te + 1
67    }
68    return 1
69}
70
71// R4 WCAG 4.1.2: every non-hidden <input> has aria-label=. returns 1 if all OK, 0 otherwise.
72func a11y_inputs_labeled(buf: *u8, n: i64) -> i64 {
73    var i: i64 = 0
74    while i >= 0 {
75        let p: i64 = a11_find(buf, i, n, "<input" as *u8)
76        if p < 0 { return 1 }
77        let te: i64 = a11_tag_end(buf, p, n)
78        var hidden: i64 = 0
79        if a11_find(buf, p, te, "type=\"hidden\"" as *u8) >= 0 { hidden = 1 }
80        if hidden == 0 { if a11_attr_nonempty(buf, p, te, "aria-label=" as *u8) == 0 { return 0 } }
81        i = te + 1
82    }
83    return 1
84}
85
86// R3 WCAG 1.3.1: heading levels not skipped (a jump of >1 going deeper = fail).
87func a11y_heading_order(buf: *u8, n: i64) -> i64 {
88    var prev: i64 = 0
89    var ok: i64 = 1
90    var i: i64 = 0
91    while i + 2 < n {
92        if (buf[i] as i64) == 60 { if (buf[i+1] as i64) == 104 {   // "<h"
93            let d: i64 = buf[i+2] as i64
94            if d >= 49 { if d <= 54 {                               // '1'..'6'
95                let lvl: i64 = d - 48
96                if prev > 0 { if lvl > prev + 1 { ok = 0 } }
97                prev = lvl
98            } }
99        } }
100        i = i + 1
101    }
102    return ok
103}
104
105// full audit: number of the 4 rules satisfied (0..4)
106func a11y_audit(buf: *u8, n: i64) -> i64 {
107    var c: i64 = 0
108    if a11y_has_lang(buf, n) == 1 { c = c + 1 }
109    if a11y_imgs_alt(buf, n) == 1 { c = c + 1 }
110    if a11y_heading_order(buf, n) == 1 { c = c + 1 }
111    if a11y_inputs_labeled(buf, n) == 1 { c = c + 1 }
112    return c
113}
nx_cms_a11y.nx source

`nx_cms_a11y.nx` source
