import type { LiveRuntimeInfo, PersistedSessionInfo } from "@/lib/types";

export type ProjectSummary = {
  cwd: string;
  name: string;
  chatCount: number;
  activeCount: number;
  streamingCount: number;
  lastActivity?: string;
};

export function basename(path: string) {
  const trimmed = path.replace(/\/$/, "");
  const parts = trimmed.split("/");
  return parts[parts.length - 1] || path;
}

export function shortenPath(path: string) {
  const parts = path.split("/").filter(Boolean);
  if (parts.length <= 3) {
    return path;
  }
  return `…/${parts.slice(-2).join("/")}`;
}

export function formatRelativeDate(value: string) {
  const date = new Date(value);
  const diffMs = Date.now() - date.getTime();
  const diffMin = Math.floor(diffMs / 60_000);
  const diffHr = Math.floor(diffMs / 3_600_000);
  const diffDay = Math.floor(diffMs / 86_400_000);

  if (diffMin < 1) {
    return "Just now";
  }
  if (diffMin < 60) {
    return `${diffMin}m ago`;
  }
  if (diffHr < 24) {
    return `${diffHr}h ago`;
  }
  if (diffDay === 1) {
    return "Yesterday";
  }
  if (diffDay < 7) {
    return `${diffDay}d ago`;
  }
  return date.toLocaleDateString(undefined, { month: "short", day: "numeric" });
}

export function formatMessageCount(count: number) {
  return count === 1 ? "1 message" : `${count} messages`;
}

export function formatChatCount(count: number) {
  return count === 1 ? "1 chat" : `${count} chats`;
}

export function chatTitle(lastMessage: string | undefined, sessionPath: string) {
  const preview = lastMessage?.replace(/\s+/g, " ").trim();
  return preview || basename(sessionPath) || "Untitled chat";
}

export function projectKey(cwd: string) {
  return cwd || "(unknown)";
}

export function projectDisplayName(cwd: string) {
  if (!cwd) {
    return "Other sessions";
  }
  return basename(cwd);
}

function upsertProject(
  projects: Map<string, ProjectSummary>,
  cwd: string,
): ProjectSummary {
  const key = projectKey(cwd);
  let project = projects.get(key);
  if (!project) {
    project = {
      cwd,
      name: projectDisplayName(cwd),
      chatCount: 0,
      activeCount: 0,
      streamingCount: 0,
    };
    projects.set(key, project);
  }
  return project;
}

export function groupByProject(
  savedProjectCwds: string[],
  liveRuntimes: LiveRuntimeInfo[],
  persistedSessions: PersistedSessionInfo[],
): ProjectSummary[] {
  const projects = new Map<string, ProjectSummary>();

  for (const cwd of savedProjectCwds) {
    upsertProject(projects, cwd);
  }

  for (const session of persistedSessions) {
    const project = projects.get(projectKey(session.cwd));
    if (!project) {
      continue;
    }
    project.chatCount += 1;
    if (!project.lastActivity || session.modified > project.lastActivity) {
      project.lastActivity = session.modified;
    }
  }

  for (const runtime of liveRuntimes) {
    const project = projects.get(projectKey(runtime.cwd));
    if (!project) {
      continue;
    }
    project.activeCount += 1;
    if (runtime.isStreaming) {
      project.streamingCount += 1;
    }
  }

  return savedProjectCwds
    .map((cwd) => projects.get(projectKey(cwd)))
    .filter((project): project is ProjectSummary => project !== undefined);
}

export function sessionsForProject(
  cwd: string,
  liveRuntimes: LiveRuntimeInfo[],
  persistedSessions: PersistedSessionInfo[],
) {
  const key = projectKey(cwd);
  const live = liveRuntimes.filter((runtime) => projectKey(runtime.cwd) === key);
  const persisted = persistedSessions
    .filter((session) => projectKey(session.cwd) === key)
    .sort((a, b) => Date.parse(b.modified) - Date.parse(a.modified));
  return { live, persisted };
}

export function projectMeta(project: ProjectSummary) {
  const parts: string[] = [];
  if (project.chatCount > 0) {
    parts.push(formatChatCount(project.chatCount));
  }
  if (project.activeCount > 0) {
    parts.push(
      project.streamingCount > 0
        ? `${project.activeCount} active · working`
        : `${project.activeCount} active`,
    );
  }
  if (project.lastActivity) {
    parts.push(formatRelativeDate(project.lastActivity));
  }
  return parts.join(" · ") || "No chats yet";
}