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# Revision-checked byte edits of keyed documents. A document is an item of a
# keyed list; an edit names the revision it was made against and commits only
# if that is still the document's (0 for one not there yet), and a failed
# event leaves everything as it was.
record Doc {
id: text
body: bytes
revision: i64
}
state docs: list of Doc by id
input show = message {
id: text
}
input edit = message {
id: text
base: i64
start: u32
remove: u32
insert: bytes
}
on show {
reply docs[show.id].body
}
on edit {
if docs.has(edit.id) {
let d = docs[edit.id]
require d.revision == edit.base
require edit.start + edit.remove <= d.body.bytes
docs[edit.id].body = d.body[0 .. edit.start] + edit.insert + d.body[edit.start + edit.remove .. d.body.bytes]
docs[edit.id].revision = d.revision + 1
} else {
require edit.base == 0 && edit.start == 0 && edit.remove == 0
docs.add(Doc { id: edit.id, body: edit.insert, revision: 1 })
}
reply edit.insert
}
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