/**
 * 図の原本の JSON を、人が書く dragon記法へ書き戻す (#3137)。
 *
 * 並べ方は決まった形に整える。JSON の欄の並び順は見ず、欄の名前で読むので、
 * 同じ内容の JSON からは毎回同じ文字列になる。書き手の行の並べ方とコメントは保たない。
 * 段の中で起きることは JSON の並び順 (起きる順) のまま書く。
 * 状態遷移図の移れる道 (`state.paths`) は、帯の宣言の後、最初の `step` より前に JSON の並びのまま書く (#3163)。
 *
 * `"` で囲むのは要る時だけにする。`[` を含む名前と、`,` か `]` を含む属性の値と、`"` で始まる字を囲む。
 * 箱は JSON の並びのまま書き、同じ区画の箱が続く所を 1 つの `group … end` にする。
 * 区画の箱が飛び飛びの時は同じ `group` を開き直す。区画の並びが箱の現れる順と違う時と、
 * 箱の無い区画がある時は、先に全ての区画を中の無い `group … end` で宣言してから開き直す。
 */
import type { Box, Diagram, DiagramEvent, Region } from "./schema";

const quote = (text: string): string => `"${text.replace(/\\/g, "\\\\").replace(/"/g, '\\"')}"`;
/** 行の終わりか `[` の前に置く名前と文 */
const name = (text: string): string => (text.includes("[") || text.startsWith('"') ? quote(text) : text);
/** `:` の前に置く字 (帯の題と、`set` の欄) */
const key = (text: string): string => (text.includes(":") || text.includes("[") || text.startsWith('"') ? quote(text) : text);
/** `strip` の行に `,` で並べる欄 */
const field = (text: string): string => (text.includes(",") || text.startsWith('"') ? quote(text) : text);
/** 属性の値 */
const value = (text: string): string => (text.includes(",") || text.includes("]") || text.startsWith('"') ? quote(text) : text);

/** 属性の並び。値の無い鍵は書かず、1 つも無ければ何も付けない */
const attrs = (pairs: [string, string | undefined][]): string => {
  const written = pairs.filter((pair): pair is [string, string] => pair[1] !== undefined);
  return written.length === 0 ? "" : ` [${written.map(([k, v]) => `${k}: ${value(v)}`).join(", ")}]`;
};

/** 名札と違う名前だけを `as` の後ろに書く */
const shown = (id: string, text: string): string => (text === id ? "" : ` as ${name(text)}`);

const declareRegion = (r: Region): string =>
  `group ${r.id}${shown(r.id, r.name)}${attrs([
    ["note", r.note],
    ["color", r.color],
    ["icon", r.icon],
  ])}`;
const declareBox = (b: Box): string =>
  `box ${b.id}${shown(b.id, b.name)}${attrs([
    ["note", b.sub],
    ["color", b.color],
    ["icon", b.icon],
  ])}`;

/** 線の行の両端と名前 */
const line = (from: string, to: string, label: string | undefined): string => `${from} -> ${to}${label === undefined ? "" : `: ${name(label)}`}`;

function event(e: DiagramEvent): string {
  switch (e.type) {
    case "edge": {
      const carry: [string, string][] = e.carry.kind === "tag" ? [["tag", e.carry.text]] : e.carry.kind === "envelope" ? [] : [["carry", e.carry.kind]];
      return `${line(e.from, e.to, e.label)}${attrs([...carry, ["side", e.labelSide]])}`;
    }
    case "action":
      return `act ${e.box}: ${e.label}`;
    case "swap":
      return `note ${e.box}: ${e.text}`;
    case "strip":
      return `set ${key(e.field)}${e.value === undefined ? "" : `: ${name(e.value)}`}${attrs([["tag", e.tag]])}`;
  }
}

/** 区画と箱の宣言の塊。塊どうしは空行で区切る */
function declarations(diagram: Diagram): string[] {
  const regions = diagram.regions ?? [];
  const runs: { region?: string; boxes: Box[] }[] = [];
  for (const b of diagram.boxes) {
    const last = runs.at(-1);
    if (last && last.region === b.region) last.boxes.push(b);
    else runs.push({ ...(b.region !== undefined ? { region: b.region } : {}), boxes: [b] });
  }
  const opened = [...new Set(runs.flatMap((run) => (run.region === undefined ? [] : [run.region])))];
  const inOrder = opened.length === regions.length && opened.every((id, i) => regions[i]?.id === id);
  const declared = new Set<string>();
  const blocks: string[] = [];
  if (!inOrder) {
    for (const r of regions) {
      blocks.push(`${declareRegion(r)}\nend`);
      declared.add(r.id);
    }
  }
  for (const run of runs) {
    const lines = run.boxes.map(declareBox);
    if (run.region === undefined) {
      blocks.push(lines.join("\n"));
      continue;
    }
    const region = regions.find((r) => r.id === run.region);
    const open = declared.has(run.region) || !region ? `group ${run.region}` : declareRegion(region);
    declared.add(run.region);
    blocks.push([open, ...lines.map((line) => `  ${line}`), "end"].join("\n"));
  }
  return blocks;
}

export function printNotation(diagram: Diagram): string {
  const blocks = [`${diagram.kind} ${name(diagram.title)}${attrs([["view", diagram.view]])}`, ...declarations(diagram)];
  if (diagram.strip) blocks.push(`strip ${key(diagram.strip.title)}: ${diagram.strip.fields.map(field).join(", ")}`);
  if (diagram.state) blocks.push(diagram.state.paths.map((p) => line(p.from, p.to, p.label)).join("\n"));
  for (const step of diagram.steps) {
    const body = step.body.split("\n");
    const say = body.length === 1 ? [`  say ${step.body}`] : ["  say", ...body.map((line) => (line === "" ? "" : `    ${line}`))];
    blocks.push(
      [`step ${step.title}`, ...say, ...(step.code === undefined ? [] : [`  code ${step.code}`]), ...step.events.map((e) => `  ${event(e)}`)].join("\n"),
    );
  }
  return `${blocks.join("\n\n")}\n`;
}