3 files changed, 217 insertions, 0 deletions
diff --git a/pngmeta/metareader.go b/pngmeta/metareader.go
new file mode 100644
index 0000000..ea726c9
--- /dev/null
+++ b/pngmeta/metareader.go
@@ -0,0 +1,107 @@
+package pngmeta
+
+import (
+	"bytes"
+	"elefant/models"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"io"
+	"os"
+	"path"
+	"strings"
+)
+
+const (
+	embType = "tEXt"
+)
+
+type PngEmbed struct {
+	Key   string
+	Value string
+}
+
+func (c PngEmbed) GetDecodedValue() (*models.CharCardSpec, error) {
+	data, err := base64.StdEncoding.DecodeString(c.Value)
+	if err != nil {
+		return nil, err
+	}
+	card := &models.CharCardSpec{}
+	if err := json.Unmarshal(data, &card); err != nil {
+		return nil, err
+	}
+	return card, nil
+}
+
+func extractChar(fname string) (*PngEmbed, error) {
+	data, err := os.ReadFile(fname)
+	if err != nil {
+		return nil, err
+	}
+	reader := bytes.NewReader(data)
+	pr, err := NewPNGStepReader(reader)
+	if err != nil {
+		return nil, err
+	}
+	for {
+		step, err := pr.Next()
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				break
+			}
+		}
+		if step.Type() != embType {
+			if _, err := io.Copy(io.Discard, step); err != nil {
+				return nil, err
+			}
+		} else {
+			buf, err := io.ReadAll(step)
+			if err != nil {
+				return nil, err
+			}
+			dataInstep := string(buf)
+			values := strings.Split(dataInstep, "\x00")
+			if len(values) == 2 {
+				return &PngEmbed{Key: values[0], Value: values[1]}, nil
+			}
+		}
+		if err := step.Close(); err != nil {
+			return nil, err
+		}
+	}
+	return nil, errors.New("failed to find embedded char in png: " + fname)
+}
+
+func ReadCard(fname, uname string) (*models.CharCard, error) {
+	pe, err := extractChar(fname)
+	if err != nil {
+		return nil, err
+	}
+	charSpec, err := pe.GetDecodedValue()
+	if err != nil {
+		return nil, err
+	}
+	return charSpec.Simplify(uname, fname), nil
+}
+
+func ReadDirCards(dirname, uname string) ([]*models.CharCard, error) {
+	files, err := os.ReadDir(dirname)
+	if err != nil {
+		return nil, err
+	}
+	resp := []*models.CharCard{}
+	for _, f := range files {
+		if !strings.HasSuffix(f.Name(), ".png") {
+			continue
+		}
+		fpath := path.Join(dirname, f.Name())
+		cc, err := ReadCard(fpath, uname)
+		if err != nil {
+			// log err
+			return nil, err
+			// continue
+		}
+		resp = append(resp, cc)
+	}
+	return resp, nil
+}
diff --git a/pngmeta/metareader_test.go b/pngmeta/metareader_test.go
new file mode 100644
index 0000000..51dadc6
--- /dev/null
+++ b/pngmeta/metareader_test.go
@@ -0,0 +1,33 @@
+package pngmeta
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestReadMeta(t *testing.T) {
+	cases := []struct {
+		Filename string
+	}{
+		{
+			Filename: "../sysprompts/default_Seraphina.png",
+		},
+		{
+			Filename: "../sysprompts/llama.png",
+		},
+	}
+	for i, tc := range cases {
+		t.Run(fmt.Sprintf("test_%d", i), func(t *testing.T) {
+			// Call the readMeta function
+			pembed, err := extractChar(tc.Filename)
+			if err != nil {
+				t.Errorf("Expected no error, but got %v", err)
+			}
+			v, err := pembed.GetDecodedValue()
+			if err != nil {
+				t.Errorf("Expected no error, but got %v\n", err)
+			}
+			fmt.Printf("%+v\n", v.Simplify("Adam"))
+		})
+	}
+}
diff --git a/pngmeta/partsreader.go b/pngmeta/partsreader.go
new file mode 100644
index 0000000..b69e4c3
--- /dev/null
+++ b/pngmeta/partsreader.go
@@ -0,0 +1,77 @@
+package pngmeta
+
+import (
+	"encoding/binary"
+	"errors"
+	"hash"
+	"hash/crc32"
+	"io"
+)
+
+var (
+	ErrCRC32Mismatch = errors.New("crc32 mismatch")
+	ErrNotPNG        = errors.New("not png")
+	ErrBadLength     = errors.New("bad length")
+)
+
+const header = "\x89PNG\r\n\x1a\n"
+
+type PngChunk struct {
+	typ         string
+	length      int32
+	r           io.Reader
+	realR       io.Reader
+	checksummer hash.Hash32
+}
+
+func (c *PngChunk) Read(p []byte) (int, error) {
+	return io.TeeReader(c.r, c.checksummer).Read(p)
+}
+
+func (c *PngChunk) Close() error {
+	var crc32 uint32
+	if err := binary.Read(c.realR, binary.BigEndian, &crc32); err != nil {
+		return err
+	}
+	if crc32 != c.checksummer.Sum32() {
+		return ErrCRC32Mismatch
+	}
+	return nil
+}
+
+func (c *PngChunk) Type() string {
+	return c.typ
+}
+
+type Reader struct {
+	r io.Reader
+}
+
+func NewPNGStepReader(r io.Reader) (*Reader, error) {
+	expectedHeader := make([]byte, len(header))
+	if _, err := io.ReadFull(r, expectedHeader); err != nil {
+		return nil, err
+	}
+	if string(expectedHeader) != header {
+		return nil, ErrNotPNG
+	}
+	return &Reader{r}, nil
+}
+
+func (r *Reader) Next() (*PngChunk, error) {
+	var length int32
+	if err := binary.Read(r.r, binary.BigEndian, &length); err != nil {
+		return nil, err
+	}
+	if length < 0 {
+		return nil, ErrBadLength
+	}
+	var rawTyp [4]byte
+	if _, err := io.ReadFull(r.r, rawTyp[:]); err != nil {
+		return nil, err
+	}
+	typ := string(rawTyp[:])
+	checksummer := crc32.NewIEEE()
+	checksummer.Write([]byte(typ))
+	return &PngChunk{typ, length, io.LimitReader(r.r, int64(length)), r.r, checksummer}, nil
+}