Add AbsoluteListOptions (#17028)

This PR adds a `ListOptions` type which is not paged but uses absolute values. It is implemented as discussed in Discord.
Extracted from #16510 to clean that PR.

models/list_options.go

@@ -10,38 +10,49 @@ import (
 	"xorm.io/xorm"
 )
 
+// Paginator is the base for different ListOptions types
+type Paginator interface {
+	GetSkipTake() (skip, take int)
+	GetStartEnd() (start, end int)
+}
+
+// getPaginatedSession creates a paginated database session
+func getPaginatedSession(p Paginator) *xorm.Session {
+	skip, take := p.GetSkipTake()
+
+	return x.Limit(take, skip)
+}
+
+// setSessionPagination sets pagination for a database session
+func setSessionPagination(sess *xorm.Session, p Paginator) *xorm.Session {
+	skip, take := p.GetSkipTake()
+
+	return sess.Limit(take, skip)
+}
+
+// setSessionPagination sets pagination for a database engine
+func setEnginePagination(e Engine, p Paginator) Engine {
+	skip, take := p.GetSkipTake()
+
+	return e.Limit(take, skip)
+}
+
 // ListOptions options to paginate results
 type ListOptions struct {
 	PageSize int
 	Page     int // start from 1
 }
 
-func (opts *ListOptions) getPaginatedSession() *xorm.Session {
+// GetSkipTake returns the skip and take values
+func (opts *ListOptions) GetSkipTake() (skip, take int) {
 	opts.setDefaultValues()
-
-	return x.Limit(opts.PageSize, (opts.Page-1)*opts.PageSize)
-}
-
-func (opts *ListOptions) setSessionPagination(sess *xorm.Session) *xorm.Session {
-	opts.setDefaultValues()
-
-	if opts.PageSize <= 0 {
-		return sess
-	}
-	return sess.Limit(opts.PageSize, (opts.Page-1)*opts.PageSize)
-}
-
-func (opts *ListOptions) setEnginePagination(e Engine) Engine {
-	opts.setDefaultValues()
-
-	return e.Limit(opts.PageSize, (opts.Page-1)*opts.PageSize)
+	return (opts.Page - 1) * opts.PageSize, opts.PageSize
 }
 
 // GetStartEnd returns the start and end of the ListOptions
 func (opts *ListOptions) GetStartEnd() (start, end int) {
-	opts.setDefaultValues()
-	start = (opts.Page - 1) * opts.PageSize
-	end = start + opts.PageSize
+	start, take := opts.GetSkipTake()
+	end = start + take
 	return
 }
 
@@ -56,3 +67,33 @@ func (opts *ListOptions) setDefaultValues() {
 		opts.Page = 1
 	}
 }
+
+// AbsoluteListOptions absolute options to paginate results
+type AbsoluteListOptions struct {
+	skip int
+	take int
+}
+
+// NewAbsoluteListOptions creates a list option with applied limits
+func NewAbsoluteListOptions(skip, take int) *AbsoluteListOptions {
+	if skip < 0 {
+		skip = 0
+	}
+	if take <= 0 {
+		take = setting.API.DefaultPagingNum
+	}
+	if take > setting.API.MaxResponseItems {
+		take = setting.API.MaxResponseItems
+	}
+	return &AbsoluteListOptions{skip, take}
+}
+
+// GetSkipTake returns the skip and take values
+func (opts *AbsoluteListOptions) GetSkipTake() (skip, take int) {
+	return opts.skip, opts.take
+}
+
+// GetStartEnd returns the start and end values
+func (opts *AbsoluteListOptions) GetStartEnd() (start, end int) {
+	return opts.skip, opts.skip + opts.take
+}