Add edit history data access

app/src/api/dataAccess/editHistory.ts

@@ -0,0 +1,64 @@
+import db from '../../db';
+import { EditHistoryEntry } from '../../frontend/models/edit-history-entry';
+
+const baseQuery = `
+        SELECT
+            log_id as revision_id,
+            forward_patch,
+            reverse_patch,
+            date_trunc('minute', log_timestamp) as revision_timestamp,
+            username,
+            building_id
+        FROM logs
+        JOIN users ON logs.user_id = users.user_id`;
+
+export function getHistoryAfterId(id: string, count: number): Promise<EditHistoryEntry[]> {
+    /** 
+     * SQL with lower time bound specified (records after ID).
+     * The outer SELECT is so that final results are sorted by descending ID
+     * (like the other queries). The inner select is sorted in ascending order
+     * so that the right rows are returned when limiting the result set.
+     */
+    return db.manyOrNone(`
+        SELECT * FROM (
+            ${baseQuery}
+            WHERE log_id > $1
+            ORDER BY log_id ASC
+            LIMIT $2
+        ) AS result_asc ORDER BY log_id DESC`,
+        [id, count]
+    );
+}
+
+export function getHistoryBeforeId(id: string, count: number): Promise<EditHistoryEntry[]> {
+    return db.manyOrNone(`
+        ${baseQuery}
+        WHERE log_id < $1
+        ORDER BY log_id DESC
+        LIMIT $2
+    `, [id, count]);
+}
+
+export async function getLatestHistory(count: number) : Promise<EditHistoryEntry[]> {
+    return await db.manyOrNone(`
+        ${baseQuery}
+        ORDER BY log_id DESC
+        LIMIT $1
+    `, [count]);
+}
+
+export async function getIdOlderThan(id: string): Promise<string> {
+    return await db.oneOrNone(`
+        SELECT MAX(log_id) as log_id
+        FROM logs
+        WHERE log_id < $1
+    `, [id]);
+}
+
+export async function getIdNewerThan(id: string): Promise<string> {
+    return await db.oneOrNone(`
+        SELECT MIN(log_id) as log_id
+        FROM logs
+        WHERE log_id > $1
+    `, [id]);
+}