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Refactor ChangesResource to handle pagination only in terms of before

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This commit is contained in:
Magnus Hoff 2017-10-22 13:16:29 +02:00
parent 50b86db597
commit 7a63fdca0e
1 changed files with 17 additions and 33 deletions
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50
src/resources/changes_resource.rs
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@ -16,7 +16,7 @@ const PAGE_SIZE: i32 = 30;
pub struct ChangesResource {
state: State,
pagination: Pagination<i32>,
before: Option<i32>,
}
impl ChangesResource {
@ -40,15 +40,12 @@ impl ChangesResource {
Ok(Self {
state,
pagination: match extra_element {
Some(x) => Pagination::Before(x.sequence_number),
None => Pagination::None
}
before: extra_element.map(|x| x.sequence_number),
})
})
),
Pagination::Before(x) => Box::new(finished(Self { state, pagination })),
Pagination::None => Box::new(finished(Self { state, pagination })),
Pagination::Before(x) => Box::new(finished(Self { state, before: Some(x) })),
Pagination::None => Box::new(finished(Self { state, before: None })),
}
}
}
@ -94,23 +91,18 @@ impl Resource for ChangesResource {
changes: &'a [Row],
}
let pagination = self.pagination.clone();
let before = self.before.clone();
let data = self.state.query_article_revision_stubs(move |query| {
use diesel::prelude::*;
use schema::article_revisions::dsl::*;
let query = query
.order(sequence_number.desc())
.limit(PAGE_SIZE as i64 + 1);
match pagination {
Pagination::After(x) => query
.filter(sequence_number.gt(x))
.order(sequence_number.asc()),
Pagination::Before(x) => query
.filter(sequence_number.lt(x))
.order(sequence_number.desc()),
Pagination::None => query
.order(sequence_number.desc()),
match before {
Some(x) => query.filter(sequence_number.lt(x)),
None => query,
}
});
@ -120,27 +112,19 @@ impl Resource for ChangesResource {
.and_then(move |(mut data, head)| {
use std::iter::Iterator;
if data.len() == 0 {
// TODO Handle degenerate case
unimplemented!("Cannot deal with empty result sets");
}
let extra_element = if data.len() > PAGE_SIZE as usize {
data.pop()
} else {
None
};
let (newer, older) = match self.pagination {
Pagination::After(x) => {
data.reverse();
(
extra_element.map(|_| NavLinks {
more: format!("?after={}", data.first().unwrap().sequence_number),
end: format!("_changes"),
}),
Some(NavLinks {
more: format!("?before={}", x + 1),
end: format!("?after=0"),
})
)
},
Pagination::Before(x) => (
let (newer, older) = match self.before {
Some(x) => (
Some(NavLinks {
more: format!("?after={}", x - 1),
end: format!("_changes"),
@ -150,7 +134,7 @@ impl Resource for ChangesResource {
end: format!("?after=0"),
})
),
Pagination::None => (
None => (
None,
extra_element.map(|_| NavLinks {
more: format!("?before={}", data.last().unwrap().sequence_number),