import yaml from "js-yaml";

export interface Pair {
  key: string;
  value: string;
}

export function parseNote(text: string): { frontmatter: Record<string, unknown>; body: string } {
  const stripped = text.replace(/^/, "");
  const m = /^---\r?\n([\s\S]*?)\r?\n---\r?\n?/.exec(stripped);
  if (!m) return { frontmatter: {}, body: stripped };
  const loaded = yaml.load(m[1]);
  const frontmatter = loaded && typeof loaded === "object" ? (loaded as Record<string, unknown>) : {};
  return { frontmatter, body: stripped.slice(m[0].length) };
}

/**
 * Convert a parsed note's frontmatter object into ordered, stringified pairs
 * suitable for display (read-only) and composition.
 */
export function docFrontmatterToPairs(docFrontmatter: Record<string, unknown>): Pair[] {
  return Object.entries(docFrontmatter).map(([key, v]) => ({ key, value: stringifyScalar(v) }));
}

/**
 * Build the final frontmatter for the post.
 *
 * Editable rows (the preset fields seeded from settings plus any custom rows
 * the user added) are authoritative: on a key collision they win over the
 * document's own merged fields, which appear first (and are shown read-only in
 * the modal). Blank-key rows are dropped; duplicate editable keys keep the last
 * value at the first position.
 */
export function composeFrontmatter(docPairs: Pair[], editableRows: Pair[], mergeDoc: boolean): Pair[] {
  const editable = editableRows.filter((r) => r.key.trim() !== "");
  const editableKeys = new Set(editable.map((r) => r.key));
  const out: Pair[] = [];
  const idx = new Map<string, number>();
  const put = (key: string, value: string) => {
    const at = idx.get(key);
    if (at !== undefined) out[at] = { key, value };
    else { idx.set(key, out.length); out.push({ key, value }); }
  };
  if (mergeDoc) for (const p of docPairs) if (!editableKeys.has(p.key)) put(p.key, p.value);
  for (const r of editable) put(r.key, r.value);
  return out;
}

function stringifyScalar(v: unknown): string {
  if (v == null) return "";
  if (v instanceof Date) return v.toISOString().slice(0, 10);
  if (typeof v === "object") return yaml.dump(v).trim();
  return String(v);
}

export function serializeFrontmatter(pairs: Pair[]): string {
  const lines = pairs.map((p) => `${p.key}: ${formatValue(p.value)}`);
  return `---\n${lines.join("\n")}\n---\n`;
}

function formatValue(v: string): string {
  if (v === "") return '""';
  const yamlSpecial = /^(true|false|null|yes|no|on|off|y|n|~)$/i.test(v);
  const isoDate = /^\d{4}-\d{2}-\d{2}$/.test(v);
  const numericLike = !isoDate && /^[+-]?(\d|\.\d)/.test(v);
  if (yamlSpecial || numericLike) return JSON.stringify(v);
  const bareSafe = /^[A-Za-z0-9_./-][A-Za-z0-9_./ -]*$/.test(v) && !/^\s|\s$/.test(v);
  return bareSafe ? v : JSON.stringify(v);
}