62 lines
1.3 KiB
Go
62 lines
1.3 KiB
Go
// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package pipe
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import (
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"sort"
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)
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// GroupFunc represents a grouping func that returns a grouping key.
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// The type alias frees us from binding to a named type.
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type GroupFunc = func(Record) (key string)
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// Group records by a key.
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type Group struct {
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sum map[string]record // metrics per group key
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keys []string // unique group keys
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key GroupFunc
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}
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// GroupBy returns a new Group.
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// It takes a group func that returns a group key.
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// The returned group will group the record using the key.
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func GroupBy(key GroupFunc) *Group {
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return &Group{
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sum: make(map[string]record),
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key: key,
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}
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}
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// Consume records for grouping.
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func (g *Group) Consume(records Iterator) error {
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return records.Each(func(r Record) error {
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k := g.key(r)
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if _, ok := g.sum[k]; !ok {
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g.keys = append(g.keys, k)
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}
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g.sum[k] = r.sum(g.sum[k])
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return nil
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})
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}
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// Each sorts and yields the grouped records.
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func (g *Group) Each(yield func(Record) error) error {
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sort.Strings(g.keys)
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for _, k := range g.keys {
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if err := yield(Record{g.sum[k]}); err != nil {
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return err
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}
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}
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return nil
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}
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