ndb: switch to nostrdb notes

This is a refactor of the codebase to use a more memory-efficient
representation of notes. It should also be much faster at decoding since
we're using a custom C json parser now.

Changelog-Changed: Improved memory usage and performance when processing events

damus/Nostr/Id.swift

@@ -0,0 +1,116 @@
+//
+//  Id.swift
+//  damus
+//
+//  Created by William Casarin on 2023-07-26.
+//
+
+import Foundation
+
+struct TagRef<T>: Hashable, Equatable, Encodable {
+    let elem: TagElem
+
+    init(_ elem: TagElem) {
+        self.elem = elem
+    }
+
+    func encode(to encoder: Encoder) throws {
+        var container = encoder.singleValueContainer()
+        try container.encode(elem.string())
+    }
+}
+
+protocol TagKey {
+    var keychar: AsciiCharacter { get }
+}
+
+protocol TagKeys {
+    associatedtype TagKeys: TagKey
+    var key: TagKeys { get }
+}
+
+protocol TagConvertible {
+    var tag: [String] { get }
+    static func from_tag(tag: TagSequence) -> Self?
+}
+
+struct QuoteId: IdType, TagKey {
+    let id: Data
+    
+    init(_ data: Data) {
+        self.id = data
+    }
+
+    var keychar: AsciiCharacter { "q" }
+}
+
+
+struct Privkey: IdType {
+    let id: Data
+
+    var nsec: String {
+        bech32_privkey(self)
+    }
+
+    init?(hex: String) {
+        guard let id = hex_decode_id(hex) else {
+            return nil
+        }
+        self.init(id)
+    }
+
+    init(_ data: Data) {
+        self.id = data
+    }
+}
+
+
+struct Hashtag: TagConvertible {
+    let hashtag: String
+
+    static func from_tag(tag: TagSequence) -> Hashtag? {
+        var i = tag.makeIterator()
+
+        guard tag.count >= 2,
+              let t0 = i.next(),
+              let chr = t0.single_char,
+              chr == "t",
+              let t1 = i.next() else {
+            return nil
+        }
+
+        return Hashtag(hashtag: t1.string())
+    }
+
+    var tag: [String] { ["t", self.hashtag] }
+    var keychar: AsciiCharacter { "t" }
+}
+
+struct ReplaceableParam: TagConvertible {
+    let param: TagElem
+
+    static func from_tag(tag: TagSequence) -> ReplaceableParam? {
+        var i = tag.makeIterator()
+
+        guard tag.count >= 2,
+              let t0 = i.next(),
+              let chr = t0.single_char,
+              chr == "d",
+              let t1 = i.next() else {
+            return nil
+        }
+
+        return ReplaceableParam(param: t1)
+    }
+
+    var tag: [String] { [self.keychar.description, self.param.string()] }
+    var keychar: AsciiCharacter { "d" }
+}
+
+struct Signature: Hashable, Equatable {
+    let data: Data
+
+    init(_ p: Data) {
+        self.data = p
+    }
+}