function parseSessionEntries(content: string): {

entries: FileEntry[];

warnings: JsonlParseWarning[];

rowByEntry: Map<FileEntry, number>;

} {

const entries: FileEntry[] = [];

const warnings: JsonlParseWarning[] = [];

const rowByEntry = new Map<FileEntry, number>();

const rows = content.split(/\r?\n/u);

for (const [index, rawLine] of rows.entries()) {

const line = rawLine.trim();

continue;

}

entries.push(parsed);

rowByEntry.set(parsed, index + 1);

} catch {

warnings.push({

source: "session",

});

}

}

return { entries, warnings };

return { entries, warnings, rowByEntry };

}

function migrateLegacySessionEntries(entries: FileEntry[]): void {

branchEntries: SessionEntry[];

warnings: JsonlParseWarning[];

}> {

const { entries: fileEntries, warnings } = parseSessionEntries(

await fsp.readFile(filePath, "utf8"),

);

const {

entries: fileEntries,

warnings,

rowByEntry,

} = parseSessionEntries(await fsp.readFile(filePath, "utf8"));

migrateLegacySessionEntries(fileEntries);

const header =

fileEntries.find((entry): entry is SessionHeader => entry.type === "session") ?? null;

const byId = new Map(entries.map((entry) => [entry.id, entry]));

const leafId = entries.at(-1)?.id ?? null;

const branchEntries: SessionEntry[] = [];

let current = leafId ? byId.get(leafId) : undefined;

while (current) {

const seen = new Set<string>();

let currentId = leafId;

while (currentId) {

if (seen.has(currentId)) {

const cycleEntry = byId.get(currentId);

warnings.push({

source: "session",

code: "cyclic-session-branch",

row: cycleEntry ? (rowByEntry.get(cycleEntry) ?? 0) : 0,

message: "Stopped trajectory session branch export at a cyclic parent link.",

});

break;

}

seen.add(currentId);

const current = byId.get(currentId);

if (!current) {

warnings.push({

source: "session",

code: "incomplete-session-branch",

row: 0,

message: "Exported the reachable session branch suffix after a missing parent link.",

});

break;

}

branchEntries.unshift(current);

current = current.parentId ? byId.get(current.parentId) : undefined;

const parentId = typeof current.parentId === "string" ? current.parentId : null;

if (parentId && !byId.has(parentId)) {

warnings.push({

source: "session",

code: "incomplete-session-branch",

row: rowByEntry.get(current) ?? 0,

message: "Exported the reachable session branch suffix after a missing parent link.",

});

break;

}

currentId = parentId;

}

return { header, leafId, branchEntries, warnings };

}