/**
 * The Site folder on disk. Only the content service reads or writes it.
 */
import { createHash } from "node:crypto";
import { existsSync, mkdirSync, readFileSync, readdirSync, renameSync, statSync, writeFileSync } from "node:fs";
import { basename, dirname, join, relative, sep } from "node:path";

export const hashText = (text: string) => createHash("sha256").update(text).digest("hex");

/**
 * Whether a path under the Site folder can hold a note. Folders starting with
 * `_` or `.` hold templates, attachments and Obsidian's own files; files
 * starting with `_` are settings notes and do count. Sync conflict copies
 * never count, so a conflict can never overwrite a page.
 */
export function isNotePath(rel: string): boolean {
  const parts = rel.split(/[\\/]/);
  const file = parts.pop() ?? "";
  if (!file.endsWith(".md") || file.startsWith(".")) return false;
  if (parts.some((p) => p.startsWith("_") || p.startsWith("."))) return false;
  if (/\(conflicted copy|\.sync-conflict-/i.test(file)) return false;
  return true;
}

export class Vault {
  constructor(readonly dir: string) {}

  read(rel: string): string | null {
    try {
      return readFileSync(join(this.dir, rel), "utf8");
    } catch {
      return null;
    }
  }

  exists(rel: string): boolean {
    return existsSync(join(this.dir, rel));
  }

  /** Write through a hidden temp file and a rename, so a reader never sees half a note. */
  write(rel: string, text: string) {
    const full = join(this.dir, rel);
    mkdirSync(dirname(full), { recursive: true });
    const tmp = join(dirname(full), `.${basename(full)}.${process.pid}.tmp`);
    writeFileSync(tmp, text);
    renameSync(tmp, full);
  }

  /** Every note path under the Site folder, relative, with `/` separators. */
  listNotes(): string[] {
    const out: string[] = [];
    const walk = (d: string) => {
      for (const e of readdirSync(d, { withFileTypes: true })) {
        if (e.name.startsWith(".")) continue;
        const full = join(d, e.name);
        const rel = relative(this.dir, full).split(sep).join("/");
        if (e.isDirectory()) {
          if (!e.name.startsWith("_")) walk(full);
        } else if (isNotePath(rel)) out.push(rel);
      }
    };
    if (existsSync(this.dir)) walk(this.dir);
    return out.sort();
  }

  /** File names in `_attachments`, for checking image links. */
  listAttachments(): string[] {
    const out: string[] = [];
    const walk = (d: string) => {
      if (!existsSync(d)) return;
      for (const e of readdirSync(d, { withFileTypes: true })) {
        if (e.isDirectory()) walk(join(d, e.name));
        else out.push(e.name);
      }
    };
    walk(join(this.dir, "_attachments"));
    return out;
  }

  /** Absolute path of an attachment by file name, for serving images. */
  attachmentPath(name: string): string | null {
    const walk = (d: string): string | null => {
      if (!existsSync(d)) return null;
      for (const e of readdirSync(d, { withFileTypes: true })) {
        const full = join(d, e.name);
        if (e.isDirectory()) {
          const found = walk(full);
          if (found) return found;
        } else if (e.name === name && statSync(full).isFile()) return full;
      }
      return null;
    };
    return walk(join(this.dir, "_attachments"));
  }
}