commit 0fc60bc54f9f1f562fe0a5cf0c20c56b9102738d
Author: jolheiser <john.olheiser@gmail.com>
Date:   Wed Dec 22 23:48:19 2021 -0600

    Initial Commit
    
    Signed-off-by: jolheiser <john.olheiser@gmail.com>

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..53094d2
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+.idea/
+/emdbed
+/emdbed.exe
\ No newline at end of file
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..433f7db
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,19 @@
+Copyright (c) 2021 John Olheiser
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4e44853
--- /dev/null
+++ b/README.md
@@ -0,0 +1,110 @@
+# emdbed
+
+Embed "things" in your markdown files.
+
+Given the same input, `emdbed` should give idempotent results.
+
+## Examples
+
+The following are generated using [readme.go](readme.go) and `go generate ./...`.
+
+An entire file:
+
+<!-- emdbed: emdbed_example_test.go -->
+```go
+package emdbed
+
+import (
+	"fmt"
+)
+
+func Example() {
+	fi, err := testdata.Open("testdata/main.md")
+	defer fi.Close()
+	out, err := Convert("testdata", fi)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(out)
+	// Output:
+	//<!-- emdbed: main.go -->
+	//```go
+	//package main
+	//
+	//import "fmt"
+	//
+	//func main() {
+	//	fmt.Println("Hello, world!")
+	//}
+	// ```
+	//<!-- /emdbed -->
+}
+
+```
+<!-- /emdbed -->
+
+Just the package:
+
+<!-- emdbed: emdbed_example_test.go L1 L1 -->
+```go
+package emdbed
+```
+<!-- /emdbed -->
+
+First line until the end of imports:
+
+<!-- emdbed: emdbed_example_test.go L1 /\)/ -->
+```go
+package emdbed
+
+import (
+	"fmt"
+)
+```
+<!-- /emdbed -->
+
+Only the example func
+
+<!-- emdbed: emdbed_example_test.go /func Example/ /(?m)^\}/ -->
+```go
+func Example() {
+	fi, err := testdata.Open("testdata/main.md")
+	defer fi.Close()
+	out, err := Convert("testdata", fi)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(out)
+	// Output:
+	//<!-- emdbed: main.go -->
+	//```go
+	//package main
+	//
+	//import "fmt"
+	//
+	//func main() {
+	//	fmt.Println("Hello, world!")
+	//}
+	// ```
+	//<!-- /emdbed -->
+}
+```
+<!-- /emdbed -->
+
+A file in another directory (choosing/overriding the language)
+
+<!-- emdbed: testdata/main.txt ~go -->
+```go
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("This file has no extension")
+}
+```
+<!-- /emdbed -->
+
+## License
+
+[MIT](LICENSE)
\ No newline at end of file
diff --git a/cmd/emdbed/main.go b/cmd/emdbed/main.go
new file mode 100644
index 0000000..f5f3b1a
--- /dev/null
+++ b/cmd/emdbed/main.go
@@ -0,0 +1,39 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	"go.jolheiser.com/emdbed"
+)
+
+func main() {
+	fs := flag.NewFlagSet("emdbed", flag.ExitOnError)
+	writeFlag := fs.Bool("write", false, "Write output")
+	writeShortFlag := fs.Bool("w", false, "Write output")
+	if err := fs.Parse(os.Args[1:]); err != nil {
+		fmt.Println(err)
+		return
+	}
+	if len(os.Args) < 2 {
+		fmt.Println("emdbed requires a file argument")
+		return
+	}
+
+	convert, err := emdbed.ConvertFile(fs.Arg(0))
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	write := *writeFlag || *writeShortFlag
+	if !write {
+		fmt.Println(convert)
+		return
+	}
+
+	if err := os.WriteFile(fs.Arg(0), []byte(convert), os.ModePerm); err != nil {
+		fmt.Println(err)
+	}
+}
diff --git a/emdbed.go b/emdbed.go
new file mode 100644
index 0000000..aa350b0
--- /dev/null
+++ b/emdbed.go
@@ -0,0 +1,81 @@
+package emdbed
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+var (
+	start = regexp.MustCompile(`(?m)^<!--\s*emdbed:\s*([^\s]+)\s*(~[\w]+)?\s*(?:(/[^/]+/|L\d+)\s*(/[^/]+/|L\d+)?)?\s*-->$`)
+	end   = regexp.MustCompile(`(?m)^<!--\s*/emdbed\s*-->$`)
+)
+
+// ConvertFile is a helper for converting a file on disk
+func ConvertFile(path string) (string, error) {
+	fi, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer fi.Close()
+	return Convert(filepath.Dir(path), fi)
+}
+
+// Convert converts an io.Reader with respect to a base directory
+func Convert(dir string, file io.Reader) (string, error) {
+	data, err := io.ReadAll(file)
+	if err != nil {
+		return "", err
+	}
+	contents := string(data)
+
+	var out strings.Builder
+	starts := start.FindAllStringSubmatchIndex(contents, -1)
+	ends := end.FindAllStringIndex(contents, -1)
+	if len(starts) != len(ends) {
+		return "", fmt.Errorf("starts (%d) != ends (%d)", len(starts), len(ends))
+	}
+	var last int
+	for idx, start := range starts {
+		out.WriteString(contents[last:start[1]])
+
+		relPath := contents[start[2]:start[3]]
+		fileContents, err := os.ReadFile(filepath.Join(dir, relPath))
+		if err != nil {
+			return "", err
+		}
+
+		lang := strings.TrimPrefix(filepath.Ext(relPath), ".")
+		if start[4] != -1 {
+			lang = contents[start[4]+1 : start[5]]
+		}
+
+		var startSel string
+		if start[6] != -1 {
+			startSel = contents[start[6]:start[7]]
+		}
+		var endSel string
+		if start[8] != -1 {
+			endSel = contents[start[8]:start[9]]
+		}
+
+		e := emdbed{
+			name:     relPath,
+			contents: string(fileContents),
+			language: lang,
+			start:    startSel,
+			end:      endSel,
+		}
+		sel, err := e.Selection()
+		if err != nil {
+			return "", err
+		}
+		out.WriteString(fmt.Sprintf("\n```%s\n%s\n```\n", e.language, sel))
+		last = ends[idx][0]
+	}
+	out.WriteString(contents[last:])
+	return out.String(), nil
+}
diff --git a/emdbed_example_test.go b/emdbed_example_test.go
new file mode 100644
index 0000000..492bb16
--- /dev/null
+++ b/emdbed_example_test.go
@@ -0,0 +1,27 @@
+package emdbed
+
+import (
+	"fmt"
+)
+
+func Example() {
+	fi, err := testdata.Open("testdata/main.md")
+	defer fi.Close()
+	out, err := Convert("testdata", fi)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(out)
+	// Output:
+	//<!-- emdbed: main.go -->
+	//```go
+	//package main
+	//
+	//import "fmt"
+	//
+	//func main() {
+	//	fmt.Println("Hello, world!")
+	//}
+	// ```
+	//<!-- /emdbed -->
+}
diff --git a/emdbed_test.go b/emdbed_test.go
new file mode 100644
index 0000000..c220302
--- /dev/null
+++ b/emdbed_test.go
@@ -0,0 +1,29 @@
+package emdbed
+
+import (
+	"embed"
+	"strings"
+	"testing"
+
+	"github.com/matryer/is"
+)
+
+//go:embed testdata
+var testdata embed.FS
+
+func TestIdempotent(t *testing.T) {
+	assert := is.NewRelaxed(t)
+
+	fi, err := testdata.Open("testdata/main.md")
+	defer fi.Close()
+	out, err := Convert("testdata", fi)
+	assert.NoErr(err) // Conversion should be successful
+
+	idem := out
+	for idx := 0; idx < 100; idx++ {
+		idem, err = Convert("testdata", strings.NewReader(idem))
+		assert.NoErr(err) // Conversion should be successful
+	}
+
+	assert.Equal(out, idem) // Original output should match after 100 tries
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..22d40e3
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module go.jolheiser.com/emdbed
+
+go 1.17
+
+require github.com/matryer/is v1.4.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..ddd6bbf
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/matryer/is v1.4.0 h1:sosSmIWwkYITGrxZ25ULNDeKiMNzFSr4V/eqBQP0PeE=
+github.com/matryer/is v1.4.0/go.mod h1:8I/i5uYgLzgsgEloJE1U6xx5HkBQpAZvepWuujKwMRU=
diff --git a/io.go b/io.go
new file mode 100644
index 0000000..adc83f9
--- /dev/null
+++ b/io.go
@@ -0,0 +1,87 @@
+package emdbed
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var endline = regexp.MustCompile(`(?m)$`)
+
+type emdbed struct {
+	name     string
+	contents string
+	language string
+	start    string
+	end      string
+}
+
+func (e emdbed) line(line int, end bool) (int, error) {
+	if line == 1 && !end {
+		return 0, nil
+	}
+	indexes := endline.FindAllStringIndex(e.contents, -1)
+	if len(indexes) < line {
+		return 0, fmt.Errorf("file %q has no line %d", e.name, line)
+	}
+	return indexes[line-1][0], nil
+}
+
+func (e emdbed) regex(pattern string, end bool) (int, error) {
+	re, err := regexp.Compile(pattern)
+	if err != nil {
+		return 0, err
+	}
+	match := re.FindStringIndex(e.contents)
+	if match == nil {
+		return 0, fmt.Errorf("file %q has no match for pattern %q", e.name, pattern)
+	}
+	var inc int
+	if end {
+		inc++
+	}
+	return match[0] + inc, nil
+}
+
+func (e emdbed) selector(selector string, end bool) (int, error) {
+	switch {
+	case strings.HasPrefix(selector, "L"):
+		line, err := strconv.Atoi(selector[1:])
+		if err != nil {
+			return 0, err
+		}
+		return e.line(line, end)
+	case strings.HasPrefix(selector, "/"):
+		pattern := strings.Trim(selector, "/")
+		return e.regex(pattern, end)
+	default:
+		return 0, fmt.Errorf("unknown selector %q", selector)
+	}
+}
+
+func (e emdbed) Start() (int, error) {
+	if e.start == "" {
+		return 0, nil
+	}
+	return e.selector(e.start, false)
+}
+
+func (e emdbed) End() (int, error) {
+	if e.end == "" {
+		return len(e.contents), nil
+	}
+	return e.selector(e.end, true)
+}
+
+func (e emdbed) Selection() (string, error) {
+	start, err := e.Start()
+	if err != nil {
+		return "", err
+	}
+	end, err := e.End()
+	if err != nil {
+		return "", err
+	}
+	return e.contents[start:end], nil
+}
diff --git a/readme.go b/readme.go
new file mode 100644
index 0000000..0f5a333
--- /dev/null
+++ b/readme.go
@@ -0,0 +1,20 @@
+//go:build generate
+
+package main
+
+import (
+	"os"
+
+	"go.jolheiser.com/emdbed"
+)
+
+//go:generate go run readme.go
+func main() {
+	convert, err := emdbed.ConvertFile("README.md")
+	if err != nil {
+		panic(err)
+	}
+	if err := os.WriteFile("README.md", []byte(convert), os.ModePerm); err != nil {
+		panic(err)
+	}
+}
diff --git a/testdata/main.go b/testdata/main.go
new file mode 100644
index 0000000..f7b60bd
--- /dev/null
+++ b/testdata/main.go
@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello, world!")
+}
diff --git a/testdata/main.md b/testdata/main.md
new file mode 100644
index 0000000..b2f9f5a
--- /dev/null
+++ b/testdata/main.md
@@ -0,0 +1,2 @@
+<!-- emdbed: main.go -->
+<!-- /emdbed -->
diff --git a/testdata/main.txt b/testdata/main.txt
new file mode 100644
index 0000000..be11d3c
--- /dev/null
+++ b/testdata/main.txt
@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("This file has no extension")
+}
\ No newline at end of file