Implement basic relative wikilink support

Closes #35. This allows hugo-obsidian to intuit absolute paths from unanchored
wikilink paths. Previously, a note at `directory/note.md` would need to be
linked using `[[directory/note]]` in order for the link to be recognized by this
tool. This change allows the shorter `[[note]]` link to be used. This is
accomplished by first walking the directory tree and storing absolute paths for
every path basename, and using this to substitute link names before rendering them.

There's no test infrastructure for this project, but IWOMM

main.go

@@ -2,22 +2,16 @@ package main
 
 import (
 	"flag"
-	"github.com/BurntSushi/toml"
-	wikilink "github.com/abhinav/goldmark-wikilink"
-	"github.com/yuin/goldmark"
 	"io/ioutil"
 	"path/filepath"
 	"time"
+
+	"github.com/BurntSushi/toml"
+	"github.com/yuin/goldmark"
 )
 
 var md goldmark.Markdown
 
-func init() {
-	md = goldmark.New(
-		goldmark.WithExtensions(&wikilink.Extender{}),
-	)
-}
-
 type Link struct {
 	Source string `json:"source"`
 	Target string `json:"target"`

parse.go

@@ -3,13 +3,15 @@ package main
 import (
 	"bytes"
 	"fmt"
-	"github.com/PuerkitoBio/goquery"
 	"io/ioutil"
 	"strings"
+
+	"github.com/PuerkitoBio/goquery"
+	"github.com/yuin/goldmark"
 )
 
 // parse single file for links
-func parse(dir, pathPrefix string) []Link {
+func parse(md goldmark.Markdown, fileIndex fileIndex, dir, pathPrefix string) []Link {
 	// read file
 	source, err := ioutil.ReadFile(dir)
 	if err != nil {
@@ -37,8 +39,10 @@ func parse(dir, pathPrefix string) []Link {
 		target = processTarget(target)
 		source := processSource(trim(dir, pathPrefix, ".md"))
 
+		target = fileIndex.resolve(target)
+
 		// fmt.Printf("  '%s' => %s\n", source, target)
-		if !strings.HasPrefix(text, "^"){
+		if !strings.HasPrefix(text, "^") {
 			links = append(links, Link{
 				Source: source,
 				Target: target,

walk.go

@@ -9,7 +9,9 @@ import (
 	"strings"
 	"time"
 
+	wikilink "github.com/abhinav/goldmark-wikilink"
 	"github.com/adrg/frontmatter"
+	"github.com/yuin/goldmark"
 	"gopkg.in/yaml.v2"
 )
 
@@ -19,6 +21,60 @@ type Front struct {
 	Tags  []string `yaml:"tags"`
 }
 
+type fileIndex struct {
+	index map[string]string
+}
+
+// resolve takes a link path and attempts to canonicalize it according to this
+// fileIndex. If a matching canonical link cannot be found, the link is returned
+// untouched.
+func (i *fileIndex) resolve(path string) string {
+	if !isInternal(path) {
+		return path
+	}
+
+	trimmedPath := strings.TrimLeft(path, "/")
+
+	// If the path has any degree of nesting built into it, treat it as an absolute path
+	if strings.Contains(path, "/") {
+		return path
+	}
+
+	resolved, ok := i.index[trimmedPath]
+	if ok {
+		target := processTarget(resolved)
+		return target
+	}
+
+	return path
+}
+
+func buildFileIndex(root, ext string, ignorePaths map[string]struct{}) (fileIndex, error) {
+	index := map[string]string{}
+	err := filepath.WalkDir(root, func(fp string, d fs.DirEntry, e error) error {
+		if e != nil {
+			return e
+		}
+
+		// path normalize fp
+		s := filepath.ToSlash(fp)
+		s = strings.ReplaceAll(s, " ", "-")
+		if _, ignored := ignorePaths[s]; ignored {
+			return nil
+		} else if filepath.Ext(d.Name()) == ext {
+			base := filepath.Base(strings.TrimSuffix(s, ".md"))
+			index[base] = strings.TrimPrefix(s, root)
+		}
+
+		return nil
+	})
+	if err != nil {
+		return fileIndex{}, err
+	}
+
+	return fileIndex{index: index}, nil
+}
+
 // recursively walk directory and return all files with given extension
 func walk(root, ext string, index bool, ignorePaths map[string]struct{}) (res []Link, i ContentIndex) {
 	fmt.Printf("Scraping %s\n", root)
@@ -32,7 +88,15 @@ func walk(root, ext string, index bool, ignorePaths map[string]struct{}) (res []
 
 	start := time.Now()
 
-	err := filepath.WalkDir(root, func(fp string, d fs.DirEntry, e error) error {
+	md := goldmark.New(
+		goldmark.WithExtensions(&wikilink.Extender{}))
+
+	fileIndex, err := buildFileIndex(root, ext, ignorePaths)
+	if err != nil {
+		panic(err)
+	}
+
+	err = filepath.WalkDir(root, func(fp string, d fs.DirEntry, e error) error {
 		if e != nil {
 			return e
 		}
@@ -69,10 +133,10 @@ func walk(root, ext string, index bool, ignorePaths map[string]struct{}) (res []
 						title = strings.TrimSuffix(filepath.Base(fileName), filepath.Ext(fileName))
 					}
 
-          // default tags
-          if matter.Tags == nil {
-            matter.Tags = []string{}
-          }
+					// default tags
+					if matter.Tags == nil {
+						matter.Tags = []string{}
+					}
 
 					// add to content and link index
 					i[source] = Content{
@@ -81,7 +145,7 @@ func walk(root, ext string, index bool, ignorePaths map[string]struct{}) (res []
 						Content:      body,
 						Tags:         matter.Tags,
 					}
-					res = append(res, parse(s, root)...)
+					res = append(res, parse(md, fileIndex, s, root)...)
 				} else {
 					fmt.Printf("[Ignored] %s\n", d.Name())
 					nPrivate++