Add more detailed docs, examples and readme (#23)

.github/release.yaml

@@ -4,7 +4,9 @@ changelog:
       labels: ["new"]
     - title: 🐛 Fixes
       labels: ["fix", "bug"]
-    - title: 📝 Dependencies
+    - title: 📖 Documentation
+      labels: ["documentation", "docs"]
+    - title: 🔗 Dependencies
       labels: ["dependencies"]
     - title: 📦 Other
       labels: ["*"]

batch.go

@@ -6,18 +6,29 @@ import (
 	"github.com/destel/rill/internal/core"
 )
 
-// Batch groups items from an input channel into batches based on a maximum size and a timeout.
-// A batch is emitted when it reaches the maximum size, the timeout expires, or the input channel closes.
-// To emit batches only when full, set the timeout to -1. This function never emits empty batches.
-// The timeout countdown starts when the first item is added to a new batch.
-// Zero timeout is not supported and will panic.
+// Batch take a stream of items and returns a stream of batches based on a maximum size and a timeout.
+//
+// A batch is emitted when one of the following conditions is met:
+//   - The batch reaches the size of n items
+//   - The time since the first item was added to the batch exceeds the timeout
+//   - The input stream is closed
+//
+// This function never emits empty batches. To disable the timeout and emit batches only based on the size,
+// set the timeout to -1. Setting the timeout to zero is not supported and will result in a panic
+//
+// This is a non-blocking ordered function that processes items sequentially.
+//
+// See the package documentation for more information on non-blocking ordered functions and error handling.
 func Batch[A any](in <-chan Try[A], n int, timeout time.Duration) <-chan Try[[]A] {
 	values, errs := ToChans(in)
 	batches := core.Batch(values, n, timeout)
 	return FromChans(batches, errs)
 }
 
-// Unbatch is the inverse of [Batch]. It takes a channel of batches and emits individual items.
+// Unbatch is the inverse of [Batch]. It takes a stream of batches and returns a stream of individual items.
+//
+// This is a non-blocking ordered function that processes items sequentially.
+// See the package documentation for more information on non-blocking ordered functions and error handling.
 func Unbatch[A any](in <-chan Try[[]A]) <-chan Try[A] {
 	batches, errs := ToChans(in)
 	values := core.Unbatch(batches)

consume.go

@@ -7,13 +7,13 @@ import (
 	"github.com/destel/rill/internal/core"
 )
 
-// ForEach applies a function f to each item in an input channel using n goroutines for parallel processing. The function
-// blocks until all items are processed or an error is encountered, either from the function f itself or from upstream.
-// In case of an error leading to early termination, ForEach ensures the input channel is drained to avoid goroutine leaks,
-// making it safe for use in environments where cleanup is crucial. The function returns the first encountered error, or nil
-// if all items were processed successfully.
-// While this function does not guarantee the order of item processing due to its concurrent nature,
-// using n = 1 results in sequential processing, as in a simple for-range loop.
+// ForEach applies a function f to each item in an input stream.
+//
+// This is a blocking unordered function that processes items concurrently using n goroutines.
+// The case when n = 1 is optimized: it does not spawn additional goroutines and processes items sequentially,
+// making the function ordered and similar to a regular for-range loop.
+//
+// See the package documentation for more information on blocking unordered functions and error handling.
 func ForEach[A any](in <-chan Try[A], n int, f func(A) error) error {
 	if n == 1 {
 		for a := range in {
@@ -66,15 +66,10 @@ func onceFunc1[T any](f func(T)) func(T) {
 	}
 }
 
-// Err returns the first error encountered in the input channel.
-// This function blocks until:
-//   - An error is found.
-//   - The end of the input channel is reached.
+// Err returns the first error encountered in the input stream or nil if there were no errors.
 //
-// If Err terminates early (before the input channel is fully consumed),
-// it initiates background draining of the remaining items in the channel. This is done
-// to prevent goroutine leaks by ensuring that all goroutines feeding the channel are allowed to complete.
-// The input channel should not be used anymore after calling this function.
+// This is a blocking ordered function that processes items sequentially.
+// See the package documentation for more information on blocking ordered functions and error handling.
 func Err[A any](in <-chan Try[A]) error {
 	defer DrainNB(in)
 
@@ -87,16 +82,11 @@ func Err[A any](in <-chan Try[A]) error {
 	return nil
 }
 
-// First returns the first value or error encountered in the input channel.
-// This function blocks until:
-//   - A value is found. In this case, the found flag is set to true.
-//   - The end of the input channel is reached. In this case, the found flag is set to false.
-//   - An error is encountered in the input channel.
+// First returns the first item or error encountered in the input stream, whichever comes first.
+// The found return flag is set to false if the stream was empty, otherwise it is set to true.
 //
-// If First terminates early (before the input channel is fully consumed),
-// it initiates background draining of the remaining items in the channel. This is done
-// to prevent goroutine leaks by ensuring that all goroutines feeding the channel are allowed to complete.
-// The input channel should not be used anymore after calling this function.
+// This is a blocking ordered function that processes items sequentially.
+// See the package documentation for more information on blocking ordered functions and error handling.
 func First[A any](in <-chan Try[A]) (value A, found bool, err error) {
 	defer DrainNB(in)
 
@@ -108,16 +98,14 @@ func First[A any](in <-chan Try[A]) (value A, found bool, err error) {
 	return
 }
 
-// Any checks if there is an item in the input channel that satisfies the condition f.
-// This function uses n goroutines for concurrency. It blocks execution until either:
-//   - A matching item is found
-//   - All items have been checked
-//   - An error is encountered in the condition function f or from the upstream
+// Any checks if there is an item in the input stream that satisfies the condition f.
+// This function returns true as soon as it finds such an item. Otherwise, it returns false.
 //
-// In case of early termination, Any ensures the input channel is drained to avoid goroutine leaks,
-// making it safe for use in environments where cleanup is crucial. The function returns the first encountered error, or nil
+// Any is a blocking unordered function that processes items concurrently using n goroutines.
+// The case when n = 1 is optimized: it does not spawn additional goroutines and processes items sequentially,
+// making the function ordered.
 //
-// The function returns true if a match is found, false otherwise, or a first encountered error.
+// See the package documentation for more information on blocking unordered functions and error handling.
 func Any[A any](in <-chan Try[A], n int, f func(A) (bool, error)) (bool, error) {
 	errBreak := errors.New("break")
 	res := false
@@ -145,16 +133,15 @@ func Any[A any](in <-chan Try[A], n int, f func(A) (bool, error)) (bool, error)
 	return res, err
 }
 
-// All checks if all items in the input channel satisfy the condition function f.
-// This function uses n goroutines for concurrency and blocks execution until:
-//   - A non-matching item is found,
-//   - All items have been checked,
-//   - An error is encountered in the condition function f or from the upstream.
+// All checks if all items in the input stream satisfy the condition f.
+// This function returns false as soon as it finds an item that does not satisfy the condition. Otherwise, it returns true,
+// including the case when the stream was empty.
 //
-// In case of early termination, All ensures the input channel is drained to avoid goroutine leaks,
-// making it safe for use in environments where cleanup is crucial. The function returns the first encountered error, or nil
+// This is a blocking unordered function that processes items concurrently using n goroutines.
+// The case when n = 1 is optimized: it does not spawn additional goroutines and processes items sequentially,
+// making the function ordered.
 //
-// Returns true if all items match the condition, false otherwise, or a first encountered error.
+// See the package documentation for more information on blocking unordered functions and error handling.
 func All[A any](in <-chan Try[A], n int, f func(A) (bool, error)) (bool, error) {
 	// Idea: x && y && z is the same as !(!x || !y || !z)
 	// So we can use Any with a negated condition to implement All

doc.go

@@ -1,5 +1,79 @@
-// Package rill is a Go toolkit designed for efficient and straightforward streaming, parallel processing, and pipeline construction.
-// It abstracts away the complexities of concurrency management, enabling developers to focus on core logic.
-// With features like lightweight integration, batch processing, error handling, and support for functional programming paradigms,
-// rill enhances productivity in building concurrent applications. It offers type-safe operations, and minimizes memory usage even for large data sets.
+// Package rill is a collection of easy-to-use functions for concurrency, streaming, batching and pipeline construction.
+// It abstracts away the complexities of concurrency, removes boilerplate, and provides a structured way to handle errors.
+// Rill is modular and can be easily integrated into existing projects: it requires no setup and allows using only the necessary functions.
+// At the same time, rill's functions can be composed into complex, concurrent, and reusable pipelines when needed.
+//
+// # Streams and Try Containers
+//
+// In this package, a stream refers to a channel of [Try] containers. A Try container is a simple struct that holds a value and an error.
+// When an "empty stream" is referred to, it means a channel of Try containers that has been closed and was never written to.
+//
+// Most functions in this package are concurrent, and the level of concurrency can be controlled by the argument n.
+// Some functions share common behaviors and characteristics, which are described below.
+//
+// # Non-blocking functions
+//
+// Functions such as [Map], [Filter], and [Batch] take a stream as an input and return a new stream as an output.
+// They do not block and return the output stream immediately. All the processing is done in the background by the goroutine pools they spawn.
+// These functions forward all errors from the input stream to the output stream.
+// Any errors returned by the user-provided functions are also sent to the output stream.
+// When such function reaches the end of the input stream, it closes the output stream, stops processing and cleans up resources.
+//
+// Such functions are designed to be composed together to build complex processing pipelines:
+//
+//	stage2 := rill.Map(input, ...)
+//	stage3 := rill.Batch(stage2, ...)
+//	stage4 := rill.Map(stage3, ...)
+//	results := rill.Unbatch(stage4, ...)
+//	// consume the results and handle errors with some blocking function
+//
+// # Blocking functions
+//
+// Functions such as [ForEach], [Reduce] and [MapReduce] are used at the last stage of the pipeline
+// to consume the stream and return the final result or error.
+//
+// Usually, these functions block until one of the following conditions is met:
+//   - The end of the stream is reached. In this case, the function returns the final result.
+//   - An error is encountered either in the input stream or in some user-provided function. In this case, the function returns the error.
+//
+// In case of an early termination (before reaching the end of the input stream), such functions initiate
+// background draining of the remaining items. This is done to prevent goroutine
+// leaks by ensuring that all goroutines feeding the stream are allowed to complete.
+// The input stream should not be used anymore after calling such functions.
+//
+// It's also possible to consume the pipeline results manually, for example using a for-range loop.
+// In this case, add a deferred call to [DrainNB] before the loop to ensure that goroutines are not leaked.
+//
+//	 defer rill.DrainNB(results)
+//
+//	 for res := range results {
+//			if res.Error != nil {
+//				return res.Error
+//			}
+//			// process res.Value
+//	 }
+//
+// # Unordered functions
+//
+// Functions such as [Map], [Filter] and [FlatMap] write items to the output stream as soon as they become available.
+// Due to the concurrent nature of these functions, the order of items in the output stream may not match the order of items in the input stream.
+// These functions prioritize performance and concurrency over maintaining the original order.
+//
+// # Ordered functions
+//
+// Functions such as [OrderedMap] or [OrderedFilter] preserve the order of items from the input stream.
+// These functions are still concurrent, but use special synchronization techniques to ensure that
+// items are written to the output stream in the same order as they were read from the input stream.
+// This additional synchronization has some overhead, but it is negligible for i/o bound workloads.
+//
+// Some other functions, such as [ToSlice], [Batch] or [First] are not concurrent and are ordered by nature.
+//
+// # Error handling
+//
+// Error handling can be non-trivial in concurrent applications. Rill simplifies this by providing a structured error handling approach.
+// As described above, all errors are automatically propagated down the pipeline to the final stage, where they can be caught.
+// This allows the pipeline to terminate after the first error is encountered and return it to the caller.
+//
+// In cases where more complex error handling logic is required, the [Catch] function can be used.
+// It allows to catch and handle errors at any point in the pipeline, providing the flexibility to handle not only the first error, but any of them.
 package rill