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Expand VitalSource chapter selections to end of HTML document
Fix an issue where selections in the VitalSource book picker could create assignments with empty page ranges, resulting in a warning being shown about being outside of the assignment regardless of the current page. When determining the endpoint of the CFI range for a selected chapter, find the next CFI which is at a level equal to or above that of the selected entry _and_ refers to a different PDF page or HTML document. Given a TOC structure like this: ``` - Chapter 1 (CFI: /2!/4, Page 2) - Chapter 1 - Section 1 (CFI: /2!/6, Page 3) - Chapter 1 - Section 12 (CFI: /2!/8, Page 4) - Chapter 2 (CFI: /4!/2, Page 5) ``` If the user selects eg. "Chapter 1 - Section 1" the selected CFI range was previously `/2!/6-/2!/8` but is now `/2!/6-/4!/2`. The page range shown in the UI would previously have been `3-4` and is now `3-5`. The reason for doing this is that the Hypothesis client discards the part of the CFIs after the "!" and treats the endpoint of the stripped CFI as exclusive. Therefore `/2!/6-/2!/8` is an empty range whereas `/2!/6-/4!/2` is a range containing the whole of the document identified by `/2`. The reason why the Hypothesis client discards the part after the "!" is because the minimum granularity at which it operates is a single HTML document or PDF page, identified by the part before the "!". Fixes hypothesis/support#153.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,68 @@ | ||
| /** | ||
| * Functions for working with EPUB Canonical Fragment Identifiers. | ||
| * | ||
| * See https://idpf.org/epub/linking/cfi/. | ||
| */ | ||
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| /** | ||
| * Strip assertions from a Canonical Fragment Identifier. | ||
| * | ||
| * Assertions are `[...]` enclosed sections which act as checks on the validity | ||
| * of numbers but do not affect the sort order. | ||
| * | ||
| * @example | ||
| * stripCFIAssertions("/6/14[chap05ref]") // returns "/6/14" | ||
| */ | ||
| export function stripCFIAssertions(cfi: string): string { | ||
| // Fast path for CFIs with no assertions. | ||
| if (!cfi.includes('[')) { | ||
| return cfi; | ||
| } | ||
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| let result = ''; | ||
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| // Has next char been escaped? | ||
| let escaped = false; | ||
|
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| // Are we in a `[...]` assertion section? | ||
| let inAssertion = false; | ||
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| for (const ch of cfi) { | ||
| if (!escaped && ch === '^') { | ||
| escaped = true; | ||
| continue; | ||
| } | ||
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| if (!escaped && ch === '[') { | ||
| inAssertion = true; | ||
| } else if (!escaped && inAssertion && ch === ']') { | ||
| inAssertion = false; | ||
| } else if (!inAssertion) { | ||
| result += ch; | ||
| } | ||
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| escaped = false; | ||
| } | ||
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| return result; | ||
| } | ||
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| /** | ||
| * Return a slice of `cfi` up to the first step indirection [1], with assertions | ||
| * removed. | ||
| * | ||
| * A typical CFI consists of a path within the table of contents to indicate | ||
| * a content document, a step indirection ("!"), then the path of an element | ||
| * within the content document. For such a CFI, this function will retain only | ||
| * the content document path. | ||
| * | ||
| * [1] https://idpf.org/epub/linking/cfi/#sec-path-indirection | ||
| * | ||
| * @example | ||
| * documentCFI('/6/152[;vnd.vst.idref=ch13_01]!/4/2[ch13_sec_1]') // Returns "/6/152" | ||
| */ | ||
| export function documentCFI(cfi: string): string { | ||
| const stripped = stripCFIAssertions(cfi); | ||
| const sepIndex = stripped.indexOf('!'); | ||
| return sepIndex === -1 ? stripped : stripped.slice(0, sepIndex); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,39 @@ | ||
| import { documentCFI, stripCFIAssertions } from '../cfi'; | ||
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| describe('cfi', () => { | ||
| describe('stripCFIAssertions', () => { | ||
| it('returns CFI without assertions unchanged', () => { | ||
| assert.equal(stripCFIAssertions('/1/2/3/10'), '/1/2/3/10'); | ||
| }); | ||
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| it('removes assertions from CFI', () => { | ||
| assert.equal(stripCFIAssertions('/1/2[chap4ref]'), '/1/2'); | ||
| assert.equal( | ||
| stripCFIAssertions('/1[part1ref]/2[chapter2ref]/3[subsectionref]'), | ||
| '/1/2/3', | ||
| ); | ||
| }); | ||
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| it('ignores escaped characters', () => { | ||
| assert.equal(stripCFIAssertions('/1/2[chap4^[ignoreme^]ref]'), '/1/2'); | ||
| assert.equal(stripCFIAssertions('/1/2[a^[b^]]/3[c^[d^]]'), '/1/2/3'); | ||
| }); | ||
| }); | ||
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| describe('documentCFI', () => { | ||
| it('returns part of CFI before first step indirection', () => { | ||
| // Typical CFI with one step indirection. | ||
| assert.equal(documentCFI('/2/4/8!/10/12'), '/2/4/8'); | ||
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| // Rarer case of CFI with multiple step indirections. | ||
| assert.equal(documentCFI('/2/4/8!/10/12!/2/4'), '/2/4/8'); | ||
| }); | ||
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| it('strips assertions', () => { | ||
| assert.equal( | ||
| documentCFI('/6/152[;vnd.vst.idref=ch13_01]!/4/2[ch13_sec_1]'), | ||
| '/6/152', | ||
| ); | ||
| }); | ||
| }); | ||
| }); |