gotools/formatting/fractaltools.go

package formatting

import (
	"encoding/json"
	"fmt"
	"sync"
)

type pathToDoc struct {
	path string
	doc  string
}

// Fractal is fractal. It is an element of itself. It ships with a Mutex
// to handle concurrent reads and writes.
type Fractal struct {
	Branches []*Fractal
	Node     string
	Leaf     string
	Ctl      sync.Mutex
}

func (t *Fractal) marshaler(ch chan string, chErr chan error) {
	if t.Leaf != "" {
		nodeJSON, err := json.Marshal(t.Node)
		if err != nil {
			chErr <- err
			return
		}
		leafJSON, err := json.Marshal(t.Leaf)
		if err != nil {
			chErr <- err
			return
		}
		ch <- fmt.Sprintf("%s: %s", nodeJSON, leafJSON)
		return
	}
	nodeJSON, err := json.Marshal(t.Node)
	if err != nil {
		chErr <- err
		return
	}
	res := fmt.Sprintf("%s: {", nodeJSON)
	subch := make(chan string)
	for _, branch := range t.Branches {
		go branch.marshaler(subch, chErr)
	}
	limit := len(t.Branches)
	for limit > 0 {
		select {
		case part := <-subch:
			if limit > 1 {
				res = fmt.Sprintf("%s%s, ", res, part)
			} else {
				res = fmt.Sprintf("%s%s}", res, part)
			}
			limit--
		}
	}
	ch <- res
	return
}

// MarshalJSON implements Marshal interface for the Fractal type
func (t *Fractal) MarshalJSON() ([]byte, error) {
	var part string
	res := "{"
	ch := make(chan string)
	chErr := make(chan error)
	limit := 1
	go t.marshaler(ch, chErr)

	for limit != 0 {
		select {
		case part = <-ch:
			if limit > 1 {
				res = fmt.Sprintf("%s%s, ", res, part)
			} else {
				res = fmt.Sprintf("%s%s", res, part)
			}
			limit--
		case err := <-chErr:
			fmt.Println("[chErr] err:", err)
			return nil, err
		}
	}
	res = fmt.Sprintf("%s}", res)
	return []byte(res), nil
}

// New initializes a new Fractal element
func (t *Fractal) New(node string) {
	t.Ctl.Lock()
	t.Node = node
	t.Ctl.Unlock()
}

// Seal adds a Node and a Leaf to it and it should be considered closed
func (t *Fractal) Seal(node, leaf string) {
	t.Ctl.Lock()
	// no need to lock as it's a leaf node
	var f Fractal
	f.Node = node
	f.Leaf = leaf
	t.Branches = append(t.Branches, &f)
	t.Ctl.Unlock()
}

// Extend is recursive and walks all the paths appending the nodes to
// the supplied fractal
func Extend(fract *Fractal, pathMap map[string][]pathToDoc, wg *sync.WaitGroup) {
	for _, paths := range pathMap {
		subPathMap := make(map[string][]pathToDoc)
		for _, path := range paths {
			subnode, subpath := splitPath(path)
			if subpath.path == "" {
				fract.Seal(subnode, subpath.doc)
			} else {
				subPathMap[subnode] = append(subPathMap[subnode], subpath)
			}
		}
		if len(subPathMap) > 0 {
			//fract.New(node)
			for k := range subPathMap {
				wg.Add(1)
				var f Fractal
				f.New(k)
				fract.Branches = append(fract.Branches, &f)
				tmp := make(map[string][]pathToDoc)
				tmp[k] = subPathMap[k]
				go Extend(&f, tmp, wg)
			}
		}
	}
	wg.Done()
}

// BuildJSON is the constructor of the fract, given a list of paths
func BuildJSON(pathsWithDocs []pathToDoc) *Fractal {
	branches := make(map[string][]pathToDoc)
	branches["/"] = pathsWithDocs
	var fract Fractal
	fract.New("/")
	var w sync.WaitGroup
	w.Add(1)
	go Extend(&fract, branches, &w)
	w.Wait()
	return &fract
}

// EncodeJSON is the main function. Given a map with all the pairs
// path:doc and a json.Encoder it actually performs the encoding
func EncodeJSON(documentedPaths map[string]string, enc *json.Encoder) {
	var pathsWithDocs []pathToDoc
	for path, doc := range documentedPaths {
		pathsWithDocs = append(pathsWithDocs, pathToDoc{trimSlashes(path), doc})
	}
	fract := BuildJSON(pathsWithDocs)
	enc.Encode(fract)
}