From e0b704e98a1f566e00b4799f598b66d486844d18 Mon Sep 17 00:00:00 2001
From: Jason Dent <jason@streetsidesoftware.nl>
Date: Fri, 20 Aug 2021 10:04:19 +0200
Subject: [PATCH] dev: ideas on caching.

---
 packages/cspell-lib/docs/cache.md             |  9 ++++
 packages/cspell-lib/src/Cache/cspell.cache.ts | 49 +++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 packages/cspell-lib/docs/cache.md
 create mode 100644 packages/cspell-lib/src/Cache/cspell.cache.ts

diff --git a/packages/cspell-lib/docs/cache.md b/packages/cspell-lib/docs/cache.md
new file mode 100644
index 00000000000..1a447d5b486
--- /dev/null
+++ b/packages/cspell-lib/docs/cache.md
@@ -0,0 +1,9 @@
+# Caching Spell Checking Results
+
+Spell checking a large project can take a lot of time.
+
+In most cases, the files do not change from run to run, so the results are not expected to change.
+
+The idea is to cache the results of the previous runs and use those same results if nothing has changed.
+
+This is also related to ignoring known issues, see [Feature: Support Known Spelling Issues · Issue #1297 · streetsidesoftware/cspell](https://github.com/streetsidesoftware/cspell/issues/1297).
diff --git a/packages/cspell-lib/src/Cache/cspell.cache.ts b/packages/cspell-lib/src/Cache/cspell.cache.ts
new file mode 100644
index 00000000000..be19e7d9c79
--- /dev/null
+++ b/packages/cspell-lib/src/Cache/cspell.cache.ts
@@ -0,0 +1,49 @@
+/**
+ * Proposed CSpell Cache file.
+ * To be stored at `./.cspell/cache/cache.json`
+ */
+
+export interface CSpellCache {
+    version: Version;
+    signature: Hash;
+    files: CachedFile[];
+}
+
+type Version = '0.1';
+
+/**
+ * Hash used. Starts with hash id. i.e. `sha1-` or `sha512-`.
+ */
+type Hash = string;
+
+type UriRelPath = string;
+
+enum IssueCode {
+    UnknownWord = 1 << 0,
+    ForbiddenWord = 1 << 1,
+    KnownIssue = 1 << 2,
+}
+
+interface CachedFile {
+    hash: Hash;
+    path: UriRelPath;
+    issues: Issue[];
+}
+
+type Issue = IssueEntry | IssueLine;
+
+interface IssueEntry {
+    line: number;
+    character: number;
+    code: IssueCode;
+    text: string;
+    len: number;
+}
+
+type IssueLine = [
+    line: IssueEntry['line'],
+    character: IssueEntry['character'],
+    code: IssueEntry['code'],
+    text: IssueEntry['text'],
+    len: IssueEntry['len']
+];