1package connections
 2
 3import (
 4	"fmt"
 5	"github.com/MichaelMure/git-bug/graphql/models"
 6	"github.com/cheekybits/genny/generic"
 7)
 8
 9type NodeType generic.Type
10type EdgeType generic.Type
11type ConnectionType generic.Type
12
13type NodeTypeEdger func(value NodeType, offset int) Edge
14
15type NodeTypeConMaker func(
16	edges []EdgeType,
17	nodes []NodeType,
18	info models.PageInfo,
19	totalCount int) (ConnectionType, error)
20
21func NodeTypeCon(source []NodeType, edger NodeTypeEdger, conMaker NodeTypeConMaker, input models.ConnectionInput) (ConnectionType, error) {
22	var nodes []NodeType
23	var edges []EdgeType
24	var pageInfo models.PageInfo
25
26	emptyCon, _ := conMaker(edges, nodes, pageInfo, 0)
27
28	offset := 0
29
30	if input.After != nil {
31		for i, value := range source {
32			edge := edger(value, i)
33			if edge.GetCursor() == *input.After {
34				// remove all previous element including the "after" one
35				source = source[i+1:]
36				offset = i + 1
37				break
38			}
39		}
40	}
41
42	if input.Before != nil {
43		for i, value := range source {
44			edge := edger(value, i+offset)
45
46			if edge.GetCursor() == *input.Before {
47				// remove all after element including the "before" one
48				break
49			}
50
51			edges = append(edges, edge.(EdgeType))
52			nodes = append(nodes, value)
53		}
54	} else {
55		edges = make([]EdgeType, len(source))
56		nodes = source
57
58		for i, value := range source {
59			edges[i] = edger(value, i+offset).(EdgeType)
60		}
61	}
62
63	if input.First != nil {
64		if *input.First < 0 {
65			return emptyCon, fmt.Errorf("first less than zero")
66		}
67
68		if len(edges) > *input.First {
69			// Slice result to be of length first by removing edges from the end
70			edges = edges[:*input.First]
71			nodes = nodes[:*input.First]
72			pageInfo.HasNextPage = true
73		}
74	}
75
76	if input.Last != nil {
77		if *input.Last < 0 {
78			return emptyCon, fmt.Errorf("last less than zero")
79		}
80
81		if len(edges) > *input.Last {
82			// Slice result to be of length last by removing edges from the start
83			edges = edges[len(edges)-*input.Last:]
84			nodes = nodes[len(nodes)-*input.Last:]
85			pageInfo.HasPreviousPage = true
86		}
87	}
88
89	return conMaker(edges, nodes, pageInfo, len(source))
90}