66 lines
1.7 KiB
Go
66 lines
1.7 KiB
Go
package response
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import (
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"net/url"
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"strconv"
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)
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// PaginationMeta is a structure included in responses for pagination.
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type PaginationMeta struct {
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Limit int `json:"limit"`
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CurrentOffset int `json:"current_offset"`
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NextOffset *int `json:"next_offset,omitempty"`
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PrevOffset *int `json:"prev_offset,omitempty"`
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NextURL string `json:"next_url,omitempty"`
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PrevURL string `json:"prev_url,omitempty"`
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}
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// NewPaginationMeta populates pagination meta data from result parameters
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func NewPaginationMeta(offset, limit int, hasMore bool, currentURL string) PaginationMeta {
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pm := PaginationMeta{
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Limit: limit,
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CurrentOffset: offset,
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}
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// Calculate next/prev offsets, leave nil if not valid pages
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nextOffset := offset + limit
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if hasMore {
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pm.NextOffset = &nextOffset
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}
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prevOffset := offset - limit
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if prevOffset < 0 {
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prevOffset = 0
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}
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if prevOffset < offset {
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pm.PrevOffset = &prevOffset
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}
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// If URL format provided, populate URLs. Intentionally swallow URL errors for now, API should
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// catch missing URLs if we call with bad URL arg (and we care about them being present).
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if currentURL != "" && pm.NextOffset != nil {
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pm.NextURL, _ = setQueryParam(currentURL, "offset", *pm.NextOffset, 0)
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}
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if currentURL != "" && pm.PrevOffset != nil {
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pm.PrevURL, _ = setQueryParam(currentURL, "offset", *pm.PrevOffset, 0)
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}
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return pm
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}
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func setQueryParam(baseURL, key string, val, defaultVal int) (string, error) {
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u, err := url.Parse(baseURL)
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if err != nil {
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return "", err
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}
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q := u.Query()
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if val == defaultVal {
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// elide param if it's the default value
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q.Del(key)
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} else {
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q.Set(key, strconv.Itoa(val))
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}
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u.RawQuery = q.Encode()
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return u.String(), nil
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}
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