From 969bd519486e7cc90239eb311e472a9d71bbb389 Mon Sep 17 00:00:00 2001
From: Tordarus <tordarus@protonmail.com>
Date: Wed, 9 Feb 2022 12:10:02 +0100
Subject: [PATCH] initial commit

---
 chan_io.go          | 29 ++++++++++++++
 forward.go          | 11 ++++++
 go.mod              |  3 ++
 group.go            | 94 +++++++++++++++++++++++++++++++++++++++++++++
 limited_runner.go   | 28 ++++++++++++++
 map.go              | 55 ++++++++++++++++++++++++++
 merge.go            | 28 ++++++++++++++
 of.go               | 60 +++++++++++++++++++++++++++++
 runner.go           |  8 ++++
 timeout.go          | 30 +++++++++++++++
 unlimited_runner.go | 19 +++++++++
 utils.go            | 18 +++++++++
 12 files changed, 383 insertions(+)
 create mode 100644 chan_io.go
 create mode 100644 forward.go
 create mode 100644 go.mod
 create mode 100644 group.go
 create mode 100644 limited_runner.go
 create mode 100644 map.go
 create mode 100644 merge.go
 create mode 100644 of.go
 create mode 100644 runner.go
 create mode 100644 timeout.go
 create mode 100644 unlimited_runner.go
 create mode 100644 utils.go

diff --git a/chan_io.go b/chan_io.go
new file mode 100644
index 0000000..5a382ea
--- /dev/null
+++ b/chan_io.go
@@ -0,0 +1,29 @@
+package channel
+
+import (
+	"fmt"
+	"io"
+	"time"
+)
+
+// WriteInto writes all given values into the channel ch.
+// Is is a shorthand for Forward(ch, AsChan(values...))
+func WriteInto[T any](ch chan<- T, values ...T) {
+	Forward(ch, AsChan(values...))
+}
+
+// WriteIntoDelayed writes all given values into the channel ch.
+// It sleeps after every write for the given amount of time.
+// It is a shorthand for Forward(ch, AsChanDelayed(time, values...))
+func WriteIntoDelayed[T any](ch chan<- T, delay time.Duration, values ...T) {
+	Forward(ch, AsChanDelayed(delay, values...))
+}
+
+// WriteIntoWriter reads all values from ch and writes them via fmt.Fprintln to all writers
+func WriteIntoWriter[T any](ch <-chan T, writers ...io.Writer) {
+	for value := range ch {
+		for _, w := range writers {
+			fmt.Fprintln(w, value)
+		}
+	}
+}
diff --git a/forward.go b/forward.go
new file mode 100644
index 0000000..5808504
--- /dev/null
+++ b/forward.go
@@ -0,0 +1,11 @@
+package channel
+
+// Forward reads all values from all sources and sends them to target.
+// It blocks until all values are forwarded and the out channel was closed.
+// Use with go keyword for non-blocking behavior
+func Forward[T any](target chan<- T, sources ...<-chan T) {
+	for value := range Merge(sources...) {
+		target <- value
+	}
+	close(target)
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..f355ce5
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.tordarus.net/Tordarus/channel
+
+go 1.18
diff --git a/group.go b/group.go
new file mode 100644
index 0000000..4078259
--- /dev/null
+++ b/group.go
@@ -0,0 +1,94 @@
+package channel
+
+import (
+	"time"
+)
+
+// GroupByTime groups all incoming values from source using the grouper function
+// and sends them to the returned channel after the given amount of time.
+// This can useful for summing or averaging values from a channel on a fixed interval
+func GroupByTime[T, G any](source <-chan T, duration time.Duration, grouper func(current G, value T) G) <-chan G {
+	out := make(chan G, cap(source))
+
+	go func() {
+		defer close(out)
+
+		ticker := time.NewTicker(duration)
+		defer ticker.Stop()
+
+		current := *new(G)
+		changed := false
+		for {
+			select {
+			case value, ok := <-source:
+				if !ok {
+					if changed {
+						out <- current
+					}
+					return
+				}
+				current = grouper(current, value)
+				changed = true
+			case <-ticker.C:
+				group := current
+				out <- group
+				current = *new(G)
+				changed = false
+			}
+		}
+	}()
+
+	return out
+}
+
+// GroupByAmount groups all incoming values from source using the grouper function
+// and sends them to the returned channel after the given amount of values were grouped.
+// This can useful for summing or averaging values from a channel for a given amount of values
+func GroupByAmount[T, G any](source <-chan T, amount int, grouper func(current G, value T) G) <-chan G {
+	out := make(chan G, cap(source))
+
+	go func() {
+		defer close(out)
+
+		current := *new(G)
+		currentAmount := 0
+		for value := range source {
+			currentAmount++
+			current = grouper(current, value)
+
+			if currentAmount%amount == 0 {
+				group := current
+				out <- group
+				current = *new(G)
+			}
+		}
+	}()
+
+	return out
+}
+
+// GroupByValue groups all incoming values from source using the grouper function
+// and sends them to the returned channel after valueFunc returns true for a given value.
+// This can useful for summing or averaging values from a channel for a given amount of values
+func GroupByValue[T, G any](source <-chan T, valueFunc func(T) bool, grouper func(current G, value T) G) <-chan G {
+	out := make(chan G, cap(source))
+
+	go func() {
+		defer close(out)
+
+		current := *new(G)
+		currentAmount := 0
+		for value := range source {
+			currentAmount++
+			current = grouper(current, value)
+
+			if valueFunc(value) {
+				group := current
+				out <- group
+				current = *new(G)
+			}
+		}
+	}()
+
+	return out
+}
diff --git a/limited_runner.go b/limited_runner.go
new file mode 100644
index 0000000..75e4630
--- /dev/null
+++ b/limited_runner.go
@@ -0,0 +1,28 @@
+package channel
+
+// LimitedRunner is a Runner which runs its methods
+// in a pre-defined amount of routines
+type LimitedRunner struct {
+	limiter chan struct{}
+}
+
+var _ Runner = &LimitedRunner{}
+
+// NewLimitedRunner returns a new LimitedRunner with the given amount
+// of allowed routines
+func NewLimitedRunner(routineLimit int) *LimitedRunner {
+	return &LimitedRunner{
+		limiter: make(chan struct{}, routineLimit),
+	}
+}
+
+// Run blocks if the limit is currently exceeded.
+// It blocks until a routine becomes available again.
+// For non-blocking behavior, use go syntax
+func (r *LimitedRunner) Run(f func()) {
+	r.limiter <- struct{}{}
+	go func() {
+		f()
+		<-r.limiter
+	}()
+}
diff --git a/map.go b/map.go
new file mode 100644
index 0000000..250c10e
--- /dev/null
+++ b/map.go
@@ -0,0 +1,55 @@
+package channel
+
+// MapParallel applies mapper to all I's coming from in and sends their return values to out while conserving input order.
+// All mappings will be done as concurrently as possible
+func MapParallel[I, O any](source <-chan I, mapper func(I) O) (out <-chan O) {
+	return MapParallelWithRunner(source, NewUnlimitedRunner(), mapper)
+}
+
+// MapParallelWithRunner behaves like MapParallel but uses runner to spawn its routines
+func MapParallelWithRunner[I, O any](source <-chan I, runner Runner, mapper func(I) O) (out <-chan O) {
+	outputChannel := make(chan O, cap(source))
+	outchannels := make(chan chan O, cap(source))
+
+	// start routine for each incoming value
+	go func(in <-chan I, outchannels chan chan O) {
+		defer close(outchannels)
+		for inputValue := range in {
+			inputValue := inputValue
+			outCh := make(chan O)
+			outchannels <- outCh
+
+			runner.Run(func() {
+				defer close(outCh)
+				outCh <- mapper(inputValue)
+			})
+		}
+	}(source, outchannels)
+
+	// gather all results in incoming order
+	go func(out chan<- O, outchannels chan chan O) {
+		defer close(out)
+		for ch := range outchannels {
+			for outputValue := range ch {
+				out <- outputValue
+			}
+		}
+	}(outputChannel, outchannels)
+
+	return outputChannel
+}
+
+// Map applies mapper to all I's coming from in and sends their return values to out while conserving input order.
+// All mappings will be done successively
+func Map[I, O any](source <-chan I, mapper func(I) O) <-chan O {
+	out := make(chan O, cap(source))
+
+	go func() {
+		defer close(out)
+		for value := range source {
+			out <- mapper(value)
+		}
+	}()
+
+	return out
+}
diff --git a/merge.go b/merge.go
new file mode 100644
index 0000000..a0a5661
--- /dev/null
+++ b/merge.go
@@ -0,0 +1,28 @@
+package channel
+
+import "sync"
+
+// Merge returns a channel in which all values of all incoming channels are sent to.
+// The values will be sent in the same order as they are received
+func Merge[T any](channels ...<-chan T) <-chan T {
+	out := make(chan T, determineBufferSize(channels))
+
+	var wg sync.WaitGroup
+	wg.Add(len(channels))
+
+	for _, ch := range channels {
+		go func(ch <-chan T) {
+			for v := range ch {
+				out <- v
+			}
+			wg.Done()
+		}(ch)
+	}
+
+	go func() {
+		wg.Wait()
+		close(out)
+	}()
+
+	return out
+}
diff --git a/of.go b/of.go
new file mode 100644
index 0000000..3395250
--- /dev/null
+++ b/of.go
@@ -0,0 +1,60 @@
+package channel
+
+// Of returns a channel containing all values
+func Of[T any](values ...T) <-chan T {
+	return AsChanDelayed(0, values...)
+}
+
+// OfDelayed behaves like Of but with a pre-defined delay between each value
+func OfDelayed[T any](delay time.Duration, values ...T) <-chan T {
+	out := make(chan T, len(values))
+
+	go func(out chan T, values []T) {
+		for i, value := range values {
+			out <- value
+			if i < len(values)-1 {
+				time.Sleep(delay)
+			}
+		}
+		close(out)
+	}(out, values)
+
+	return out
+}
+
+// OfDelayedFunc behaves like OfDelayed but accepts a function to determine the delay
+func OfDelayedFunc[T any](delayFunc func(value T) time.Duration, values ...T) <-chan T {
+	out := make(chan T, len(values))
+
+	go func(out chan T, values []T) {
+		for i, value := range values {
+			out <- value
+			if i < len(values)-1 {
+				time.Sleep(delayFunc(value))
+			}
+		}
+		close(out)
+	}(out, values)
+
+	return out
+}
+
+// OfFunc returns a channel containing the return values of successively calling f
+// It closes the channel as soon as ctx is done
+func OfFunc[T any](ctx context.Context, buffer int, f func() T) <-chan T {
+	out := make(chan T, buffer)
+
+	go func() {
+		defer close(out)
+
+		for ctx.Err() == nil {
+			select {
+			case out <- f():
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	return out
+}
diff --git a/runner.go b/runner.go
new file mode 100644
index 0000000..7de9e36
--- /dev/null
+++ b/runner.go
@@ -0,0 +1,8 @@
+package channel
+
+// Runner is any runnable environment
+type Runner interface {
+	// Run runs f in the Runners environment
+	// It might be blocking or non-blocking depending on Runners implementation
+	Run(f func())
+}
diff --git a/timeout.go b/timeout.go
new file mode 100644
index 0000000..806037a
--- /dev/null
+++ b/timeout.go
@@ -0,0 +1,30 @@
+package channel
+
+import "time"
+
+// CloseOnTimeout returns a channel which receives all values from all sources in order of arrival.
+// If no source is sending a value in the given timeout duration, the channel will be closed
+func CloseOnTimeout[T any](timeout time.Duration, sources ...<-chan T) <-chan T {
+	input := Merge(sources...)
+	output := make(chan T, cap(input))
+
+	go func() {
+		defer close(output)
+
+		for {
+			timer := time.NewTimer(timeout)
+
+			select {
+			case value, ok := <-input:
+				if !ok {
+					return
+				}
+				output <- value
+			case <-timer.C:
+				return
+			}
+		}
+	}()
+
+	return output
+}
diff --git a/unlimited_runner.go b/unlimited_runner.go
new file mode 100644
index 0000000..58e05c3
--- /dev/null
+++ b/unlimited_runner.go
@@ -0,0 +1,19 @@
+package channel
+
+// UnlimitedRunner is a Runner which runs each method
+// in its own routine
+type UnlimitedRunner struct {
+}
+
+var _ Runner = &UnlimitedRunner{}
+
+// NewUnlimitedRunner returns a new LimitedRunner with the given amount
+// of allowed routines
+func NewUnlimitedRunner() *UnlimitedRunner {
+	return &UnlimitedRunner{}
+}
+
+// Run always returns immediately
+func (r *UnlimitedRunner) Run(f func()) {
+	go f()
+}
diff --git a/utils.go b/utils.go
new file mode 100644
index 0000000..43a3baa
--- /dev/null
+++ b/utils.go
@@ -0,0 +1,18 @@
+package channel
+
+import (
+	"context"
+	"time"
+)
+
+func determineBufferSize[T any](channels []<-chan T) int {
+	if len(channels) == 0 {
+		return 0
+	}
+
+	bufSize := 0
+	for _, ch := range channels {
+		bufSize += cap(ch)
+	}
+	return bufSize / len(channels)
+}