Add core packages, configuration system, and initial application structure

pkg/encoders/text/escape.go

@@ -0,0 +1,127 @@
+package text
+
+// NostrEscape for JSON encoding according to RFC8259.
+//
+// This is the efficient implementation based on the NIP-01 specification:
+//
+// To prevent implementation differences from creating a different event ID for
+// the same event, the following rules MUST be followed while serializing:
+//
+//	No whitespace, line breaks or other unnecessary formatting should be included
+//	in the output JSON. No characters except the following should be escaped, and
+//	instead should be included verbatim:
+//
+//	- A line break, 0x0A, as \n
+//	- A double quote, 0x22, as \"
+//	- A backslash, 0x5C, as \\
+//	- A carriage return, 0x0D, as \r
+//	- A tab character, 0x09, as \t
+//	- A backspace, 0x08, as \b
+//	- A form feed, 0x0C, as \f
+//
+//	UTF-8 should be used for encoding.
+func NostrEscape(dst, src []byte) []byte {
+	l := len(src)
+	for i := 0; i < l; i++ {
+		c := src[i]
+		switch {
+		case c == '"':
+			dst = append(dst, '\\', '"')
+		case c == '\\':
+			// if i+1 < l && src[i+1] == 'u' || i+1 < l && src[i+1] == '/' {
+			if i+1 < l && src[i+1] == 'u' {
+				dst = append(dst, '\\')
+			} else {
+				dst = append(dst, '\\', '\\')
+			}
+		case c == '\b':
+			dst = append(dst, '\\', 'b')
+		case c == '\t':
+			dst = append(dst, '\\', 't')
+		case c == '\n':
+			dst = append(dst, '\\', 'n')
+		case c == '\f':
+			dst = append(dst, '\\', 'f')
+		case c == '\r':
+			dst = append(dst, '\\', 'r')
+		default:
+			dst = append(dst, c)
+		}
+	}
+	return dst
+}
+
+// NostrUnescape reverses the operation of NostrEscape except instead of
+// appending it to the provided slice, it rewrites it, eliminating a memory
+// copy. Keep in mind that the original JSON will be mangled by this operation,
+// but the resultant slices will cost zero allocations.
+func NostrUnescape(dst []byte) (b []byte) {
+	var r, w int
+	for ; r < len(dst); r++ {
+		if dst[r] == '\\' {
+			r++
+			c := dst[r]
+			switch {
+
+			// nip-01 specifies the following single letter C-style escapes for control
+			// codes under 0x20.
+			//
+			// no others are specified but must be preserved, so only these can be
+			// safely decoded at runtime as they must be re-encoded when marshalled.
+			case c == '"':
+				dst[w] = '"'
+				w++
+			case c == '\\':
+				dst[w] = '\\'
+				w++
+			case c == 'b':
+				dst[w] = '\b'
+				w++
+			case c == 't':
+				dst[w] = '\t'
+				w++
+			case c == 'n':
+				dst[w] = '\n'
+				w++
+			case c == 'f':
+				dst[w] = '\f'
+				w++
+			case c == 'r':
+				dst[w] = '\r'
+				w++
+
+				// special cases for non-nip-01 specified json escapes (must be preserved for ID
+				// generation).
+			case c == 'u':
+				dst[w] = '\\'
+				w++
+				dst[w] = 'u'
+				w++
+			case c == '/':
+				dst[w] = '\\'
+				w++
+				dst[w] = '/'
+				w++
+
+			// special case for octal escapes (must be preserved for ID generation).
+			case c >= '0' && c <= '9':
+				dst[w] = '\\'
+				w++
+				dst[w] = c
+				w++
+
+				// anything else after a reverse solidus just preserve it.
+			default:
+				dst[w] = dst[r]
+				w++
+				dst[w] = c
+				w++
+			}
+		} else {
+			dst[w] = dst[r]
+			w++
+		}
+	}
+	b = dst[:w]
+	return
+}