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package connections
import (
"fmt"
"github.com/MichaelMure/git-bug/graphql/models"
"github.com/cheekybits/genny/generic"
)
// NodeType define the node type handled by this relay connection
type NodeType generic.Type
// EdgeType define the edge type handled by this relay connection
type EdgeType generic.Type
// ConnectionType define the connection type handled by this relay connection
type ConnectionType generic.Type
// NodeTypeEdgeMaker define a function that take a NodeType and an offset and
// create an Edge.
type NodeTypeEdgeMaker func(value NodeType, offset int) Edge
// NodeTypeConMaker define a function that create a ConnectionType
type NodeTypeConMaker func(
edges []EdgeType,
nodes []NodeType,
info models.PageInfo,
totalCount int) (ConnectionType, error)
// NodeTypeCon will paginate a source according to the input of a relay connection
func NodeTypeCon(source []NodeType, edgeMaker NodeTypeEdgeMaker, conMaker NodeTypeConMaker, input models.ConnectionInput) (ConnectionType, error) {
var nodes []NodeType
var edges []EdgeType
var cursors []string
var pageInfo models.PageInfo
emptyCon, _ := conMaker(edges, nodes, pageInfo, 0)
offset := 0
if input.After != nil {
for i, value := range source {
edge := edgeMaker(value, i)
if edge.GetCursor() == *input.After {
// remove all previous element including the "after" one
source = source[i+1:]
offset = i + 1
break
}
}
}
if input.Before != nil {
for i, value := range source {
edge := edgeMaker(value, i+offset)
if edge.GetCursor() == *input.Before {
// remove all after element including the "before" one
break
}
edges = append(edges, edge.(EdgeType))
cursors = append(cursors, edge.GetCursor())
nodes = append(nodes, value)
}
} else {
edges = make([]EdgeType, len(source))
cursors = make([]string, len(source))
nodes = source
for i, value := range source {
edge := edgeMaker(value, i+offset)
edges[i] = edge.(EdgeType)
cursors[i] = edge.GetCursor()
}
}
if input.First != nil {
if *input.First < 0 {
return emptyCon, fmt.Errorf("first less than zero")
}
if len(edges) > *input.First {
// Slice result to be of length first by removing edges from the end
edges = edges[:*input.First]
cursors = cursors[:*input.First]
nodes = nodes[:*input.First]
pageInfo.HasNextPage = true
}
}
if input.Last != nil {
if *input.Last < 0 {
return emptyCon, fmt.Errorf("last less than zero")
}
if len(edges) > *input.Last {
// Slice result to be of length last by removing edges from the start
edges = edges[len(edges)-*input.Last:]
cursors = cursors[len(cursors)-*input.Last:]
nodes = nodes[len(nodes)-*input.Last:]
pageInfo.HasPreviousPage = true
}
}
// Fill up pageInfo cursors
if len(cursors) > 0 {
pageInfo.StartCursor = cursors[0]
pageInfo.EndCursor = cursors[len(cursors)-1]
}
return conMaker(edges, nodes, pageInfo, len(source))
}
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