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writer.go
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writer.go
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// The MIT License (MIT)
//
// Copyright (c) 2020 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package pagination
type (
writer struct {
writeFn WriteFn
shouldFlushFn ShouldFlushFn
flushedPages []PageToken
page Page
}
)
// NewWriter constructs a new Writer
func NewWriter(
writeFn WriteFn,
shouldFlushFn ShouldFlushFn,
startingPage PageToken,
) Writer {
return &writer{
writeFn: writeFn,
shouldFlushFn: shouldFlushFn,
flushedPages: nil,
page: Page{
Entities: nil,
CurrentToken: startingPage,
},
}
}
// Add adds entity to buffer and flushes if provided shouldFlushFn indicates the page should be flushed.
func (w *writer) Add(e Entity) error {
w.page.Entities = append(w.page.Entities, e)
if !w.shouldFlushFn(w.page) {
return nil
}
return w.Flush()
}
// Flush flushes the buffer.
func (w *writer) Flush() error {
nextPageToken, err := w.writeFn(w.page)
if err != nil {
return err
}
w.flushedPages = append(w.flushedPages, w.page.CurrentToken)
w.page = Page{
Entities: nil,
CurrentToken: nextPageToken,
}
return nil
}
// FlushIfNotEmpty flushes the buffer if and only if it is not empty
func (w *writer) FlushIfNotEmpty() error {
if len(w.page.Entities) == 0 {
return nil
}
return w.Flush()
}
// FlushedPages returns all pages which have been successfully flushed.
func (w *writer) FlushedPages() []PageToken {
return w.flushedPages
}
// FirstFlushedPage returns the first page that was flushed or nil if no pages have been flushed.
func (w *writer) FirstFlushedPage() PageToken {
if len(w.flushedPages) == 0 {
return nil
}
return w.flushedPages[0]
}
// LastFlushedPage returns the last page that was flushed or nil if no pages have been flushed
func (w *writer) LastFlushedPage() PageToken {
if len(w.flushedPages) == 0 {
return nil
}
return w.flushedPages[len(w.flushedPages)-1]
}