wehub-resource-sync
50 lines
1.8 KiB
Swift
50 lines
1.8 KiB
Swift
import Foundation
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/// Incremental backing for the document-global list indent unit.
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///
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/// Replicates `EditorTextView.detectListIndentUnit` exactly — any
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/// tab-indented list line forces 4; otherwise the smallest space indent of
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/// any list line; 4 when none — but as a histogram that can be updated per
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/// block on the edit path instead of rescanning the whole document per
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/// keystroke. Block contents tile the document's lines exactly (merged
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/// constructs keep their inner newlines), so adding/removing block contents
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/// is equivalent to rescanning those lines.
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struct ListIndentState {
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private(set) var tabLines = 0
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private(set) var histogram: [Int: Int] = [:]
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var unit: Int {
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if tabLines > 0 { return 4 }
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return histogram.keys.min() ?? 4
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}
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mutating func add(_ content: String) { scan(content, sign: 1) }
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mutating func remove(_ content: String) { scan(content, sign: -1) }
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static func build(from source: String) -> ListIndentState {
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var state = ListIndentState()
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state.add(source)
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return state
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}
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private mutating func scan(_ content: String, sign: Int) {
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for line in content.split(separator: "\n", omittingEmptySubsequences: false) {
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var spaces = 0
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var sawTab = false
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for ch in line {
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if ch == " " { spaces += 1 }
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else if ch == "\t" { sawTab = true; break }
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else { break }
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}
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let rest = line.drop(while: { $0 == " " || $0 == "\t" })
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guard EditorTextView.startsWithListMarker(rest) else { continue }
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if sawTab {
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tabLines += sign
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} else if spaces > 0 {
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let count = (histogram[spaces] ?? 0) + sign
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histogram[spaces] = count <= 0 ? nil : count
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}
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}
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}
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}
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