// Package envelope provides marshal/unmarshal for all nostr protocol envelope types.
package envelope

import (
	"io"
)

// Identify extracts the label from a nostr envelope JSON array.
func Identify(b []byte) (t string, rem []byte, err error) {
	var openBrackets, openQuotes, afterQuotes bool
	var label []byte
	rem = b
	for ; len(rem) > 0; rem = rem[1:] {
		if !openBrackets && rem[0] == '[' {
			openBrackets = true
		} else if openBrackets {
			if !openQuotes && rem[0] == '"' {
				openQuotes = true
			} else if afterQuotes {
				if rem[0] == ',' {
					rem = rem[1:]
					return
				}
			} else if openQuotes {
				for i := range rem {
					if rem[i] == '"' {
						label = rem[:i]
						rem = rem[i:]
						t = string(label)
						afterQuotes = true
						break
					}
				}
			}
		}
	}
	return
}

// Marshaller is a function signature for marshalling envelope content.
type Marshaller func(dst []byte) (b []byte)

// Marshal wraps content in a JSON array envelope with the given label.
func Marshal(dst []byte, label string, m Marshaller) (b []byte) {
	b = dst
	b = append(b, '[', '"')
	b = append(b, label...)
	b = append(b, '"', ',')
	b = m(b)
	b = append(b, ']')
	return
}

// SkipToTheEnd scans forward to the closing bracket of an envelope.
func SkipToTheEnd(dst []byte) (rem []byte, err error) {
	if len(dst) == 0 {
		return
	}
	rem = dst
	for ; len(rem) > 0; rem = rem[1:] {
		if rem[0] == ']' {
			rem = rem[:0]
			return
		}
	}
	err = io.EOF
	return
}