session-viewer/src/server/services/session-parser.ts

import fs from "fs/promises";
import type { ParsedMessage, ProgressSubtype } from "../../shared/types.js";

/**
 * Real Claude Code JSONL format (verified from actual session files):
 *
 * Every line has: { type, uuid?, timestamp?, ... }
 *
 * type="user"      → { message: { role: "user", content: string | ContentBlock[] }, uuid, timestamp }
 * type="assistant"  → { message: { role: "assistant", content: ContentBlock[] }, uuid, timestamp }
 * type="progress"   → { data: { type, hookEvent?, status?, ... }, uuid, timestamp }
 * type="summary"    → { summary: string, leafUuid }
 * type="file-history-snapshot" → { snapshot: { ... }, messageId }
 * type="system"     → { subtype: "turn_duration", durationMs, ... } (metadata, not display)
 * type="queue-operation" → internal (not display)
 *
 * ContentBlock: { type: "text", text } | { type: "thinking", thinking } | { type: "tool_use", name, input } | { type: "tool_result", content, tool_use_id }
 */

interface ContentBlock {
  type: string;
  id?: string;
  text?: string;
  thinking?: string;
  name?: string;
  input?: Record<string, unknown>;
  tool_use_id?: string;
  content?: string | ContentBlock[];
}

interface RawLine {
  type?: string;
  uuid?: string;
  timestamp?: string;
  parentToolUseID?: string;
  message?: {
    role?: string;
    content?: string | ContentBlock[];
  };
  data?: Record<string, unknown>;
  summary?: string;
  snapshot?: Record<string, unknown>;
  subtype?: string;
}

export async function parseSession(
  filePath: string
): Promise<ParsedMessage[]> {
  let content: string;
  try {
    content = await fs.readFile(filePath, "utf-8");
  } catch {
    return [];
  }

  return parseSessionContent(content);
}

export function parseSessionContent(content: string): ParsedMessage[] {
  const messages: ParsedMessage[] = [];
  const lines = content.split("\n").filter((l) => l.trim());

  for (let i = 0; i < lines.length; i++) {
    let parsed: RawLine;
    try {
      parsed = JSON.parse(lines[i]);
    } catch {
      continue; // Skip malformed lines
    }

    const extracted = extractMessages(parsed, i);
    messages.push(...extracted);
  }

  return messages;
}

function extractMessages(raw: RawLine, rawIndex: number): ParsedMessage[] {
  const messages: ParsedMessage[] = [];
  const type = raw.type;
  const uuid = raw.uuid || `generated-${rawIndex}`;
  const timestamp = raw.timestamp;

  // Progress/hook messages - content is in `data`, not `content`
  if (type === "progress") {
    const data = raw.data;
    const progressText = data
      ? formatProgressData(data)
      : "Progress event";
    const dataType = typeof data?.type === "string" ? data.type : "";
    const progressSubtype = deriveProgressSubtype(dataType);
    messages.push({
      uuid,
      category: "hook_progress",
      content: progressText,
      timestamp,
      rawIndex,
      parentToolUseId: raw.parentToolUseID,
      progressSubtype,
    });
    return messages;
  }

  // File history snapshot
  if (type === "file-history-snapshot") {
    messages.push({
      uuid,
      category: "file_snapshot",
      content: JSON.stringify(raw.snapshot || raw, null, 2),
      timestamp,
      rawIndex,
    });
    return messages;
  }

  // Summary message - text is in `summary` field, not `content`
  if (type === "summary") {
    messages.push({
      uuid,
      category: "summary",
      content: raw.summary || "",
      timestamp,
      rawIndex,
    });
    return messages;
  }

  // System metadata (turn_duration etc.) - skip, not user-facing
  if (type === "system" || type === "queue-operation") {
    return messages;
  }

  // User and assistant messages - content is in `message.content`
  const role = raw.message?.role;
  const content = raw.message?.content;

  if ((type === "user" || role === "user") && content !== undefined) {
    if (typeof content === "string") {
      const category = detectSystemReminder(content)
        ? "system_message"
        : "user_message";
      messages.push({
        uuid,
        category,
        content,
        timestamp,
        rawIndex,
      });
    } else if (Array.isArray(content)) {
      for (const block of content) {
        if (block.type === "tool_result") {
          const resultText =
            typeof block.content === "string"
              ? block.content
              : Array.isArray(block.content)
                ? block.content
                    .map((b: ContentBlock) => b.text || "")
                    .join("\n")
                : JSON.stringify(block.content);
          messages.push({
            uuid: `${uuid}-tr-${block.tool_use_id || rawIndex}`,
            category: "tool_result",
            content: resultText,
            toolUseId: block.tool_use_id,
            timestamp,
            rawIndex,
          });
        } else if (block.type === "text") {
          const text = block.text || "";
          const category = detectSystemReminder(text)
            ? "system_message"
            : "user_message";
          messages.push({
            uuid: `${uuid}-text-${rawIndex}`,
            category,
            content: text,
            timestamp,
            rawIndex,
          });
        }
      }
    }
    return messages;
  }

  if ((type === "assistant" || role === "assistant") && content !== undefined) {
    if (typeof content === "string") {
      messages.push({
        uuid,
        category: "assistant_text",
        content,
        timestamp,
        rawIndex,
      });
    } else if (Array.isArray(content)) {
      for (let j = 0; j < content.length; j++) {
        const block = content[j];
        const blockUuid = `${uuid}-${j}`;
        if (block.type === "thinking") {
          messages.push({
            uuid: blockUuid,
            category: "thinking",
            content: block.thinking || block.text || "",
            timestamp,
            rawIndex,
          });
        } else if (block.type === "text") {
          messages.push({
            uuid: blockUuid,
            category: "assistant_text",
            content: block.text || "",
            timestamp,
            rawIndex,
          });
        } else if (block.type === "tool_use") {
          messages.push({
            uuid: blockUuid,
            category: "tool_call",
            content: `Tool: ${block.name}`,
            toolName: block.name,
            toolInput: JSON.stringify(block.input, null, 2),
            timestamp,
            rawIndex,
            toolUseId: block.id,
          });
        }
      }
    }
    return messages;
  }

  return messages;
}

function formatProgressData(data: Record<string, unknown>): string {
  const parts: string[] = [];
  if (data.hookEvent) parts.push(`Hook: ${data.hookEvent}`);
  if (data.hookName) parts.push(`${data.hookName}`);
  if (data.toolName) parts.push(`Tool: ${data.toolName}`);
  if (data.status) parts.push(`Status: ${data.status}`);
  if (data.serverName) parts.push(`Server: ${data.serverName}`);
  if (parts.length > 0) return parts.join(" | ");
  return JSON.stringify(data);
}

function detectSystemReminder(text: string): boolean {
  return text.includes("<system-reminder>") || text.includes("</system-reminder>");
}

function deriveProgressSubtype(dataType: string): ProgressSubtype {
  if (dataType === "bash_progress") return "bash";
  if (dataType === "mcp_progress") return "mcp";
  if (dataType === "agent_progress") return "agent";
  return "hook";
}