import "server-only";

import type { AiGroupContext } from "@/types/ai";

// This app is single-user/self-hosted scale (see lib/access.ts's comments
// on Projects being single-owner for now) -- there's no retrieval/ranking
// here, the whole relevant dataset just goes straight into the prompt,
// truncated only by the hard caps below. If a board ever grows large
// enough for this to blow the model's context window, the fix is a
// RAG-style retrieval step, not a bigger cap.
const NOTE_CHAR_CAP = 4_000;
const DETAILS_CHAR_CAP = 300;
const TOTAL_CHAR_CAP = 60_000;

function truncate(text: string, max: number): string {
  const trimmed = text.trim();
  if (trimmed.length <= max) return trimmed;
  return `${trimmed.slice(0, max)}… [truncated]`;
}

function formatTodoLine(todo: {
  title: string;
  details: string | null;
  completed: boolean;
  completedAt: string | null;
}): string {
  const box = todo.completed ? "[x]" : "[ ]";
  const doneNote = todo.completed && todo.completedAt ? ` (done ${todo.completedAt.slice(0, 10)})` : "";
  const details = todo.details?.trim() ? ` — ${truncate(todo.details, DETAILS_CHAR_CAP)}` : "";
  return `- ${box} ${todo.title}${doneNote}${details}`;
}

/** Renders one group's notes + todos as compact markdown-ish prompt text. */
export function formatGroupForPrompt(
  group: {
    title: string;
    noteContent: string;
    todos: { title: string; details: string | null; completed: boolean; completedAt: string | null }[];
  },
  opts?: { archived?: boolean }
): string {
  const openCount = group.todos.filter((t) => !t.completed).length;
  const doneCount = group.todos.length - openCount;
  const notes = group.noteContent.trim()
    ? truncate(group.noteContent, NOTE_CHAR_CAP)
    : "(no notes)";
  const todoLines = group.todos.length > 0
    ? group.todos.map(formatTodoLine).join("\n")
    : "(no to-dos)";
  const archivedTag = opts?.archived ? " [archived]" : "";

  return `Group${archivedTag}: "${group.title}"\n\nNotes:\n${notes}\n\nTo-dos (${openCount} open, ${doneCount} done):\n${todoLines}`;
}

/**
 * Renders every group the user can see, grouped by board (Home/Project)
 * then category, for the global chat's system prompt. Archived groups
 * are marked inline rather than omitted, so historical questions stay
 * answerable.
 */
export function formatAllGroupsForPrompt(groups: AiGroupContext[]): string {
  const byScope = new Map<string, Map<string, AiGroupContext[]>>();
  for (const group of groups) {
    if (!byScope.has(group.scopeLabel)) byScope.set(group.scopeLabel, new Map());
    const byCategory = byScope.get(group.scopeLabel)!;
    if (!byCategory.has(group.categoryName)) byCategory.set(group.categoryName, []);
    byCategory.get(group.categoryName)!.push(group);
  }

  const sections: string[] = [];
  for (const [scopeLabel, byCategory] of byScope) {
    sections.push(`# ${scopeLabel}`);
    for (const [categoryName, categoryGroups] of byCategory) {
      sections.push(`## Category: ${categoryName}`);
      for (const group of categoryGroups) {
        const formatted = formatGroupForPrompt(
          { title: group.groupTitle, noteContent: group.noteContent, todos: group.todos },
          { archived: group.archived }
        );
        sections.push(`### ${formatted}`);
      }
    }
  }

  let result = sections.join("\n\n");
  if (result.length > TOTAL_CHAR_CAP) {
    result = `${result.slice(0, TOTAL_CHAR_CAP)}\n\n[... additional groups omitted for length ...]`;
  }
  return result;
}