import type { EpisodeConfig, StructuredScript } from "../types";

const FORMAT_GUIDANCE: Record<EpisodeConfig["format"], string> = {
  SOLO: "A single host speaking directly to the listener. Use only the host speaker.",
  INTERVIEW:
    "A host interviewing a guest. Alternate naturally between host questions and guest answers.",
  MULTI_HOST:
    "A panel of co-hosts in lively conversation. Distribute lines across all speakers and let them react to each other.",
};

/** Roughly 150 spoken words per minute → target word budget for the whole episode. */
function wordBudget(minutes: number): number {
  return Math.round(minutes * 150);
}

export function buildScriptMessages(config: EpisodeConfig) {
  const speakerList = config.speakers
    .map((s) => `- key "${s.speakerKey}" = ${s.displayName}`)
    .join("\n");

  const system = [
    "You are an expert podcast scriptwriter and showrunner.",
    "You write natural, engaging, spoken-word scripts that sound great when read aloud by AI voices.",
    "Avoid stage directions, sound-effect notes, and parentheticals — output only spoken dialogue.",
    "Return STRICT JSON only, matching the requested schema. Do not include markdown fences.",
  ].join(" ");

  const user = [
    `Write a complete podcast episode script in ${config.language}.`,
    "",
    `Topic: ${config.topic}`,
    `Tone: ${config.tone}`,
    `Format: ${config.format} — ${FORMAT_GUIDANCE[config.format]}`,
    config.audience ? `Target audience: ${config.audience}` : "",
    `Approximate length: ${config.targetLengthMin} minutes (~${wordBudget(
      config.targetLengthMin
    )} words total).`,
    "",
    "Speakers (use ONLY these keys in `speakerKey`):",
    speakerList,
    "",
    "Structure the episode into 3–6 sections (e.g. intro, main segments, outro).",
    "Each section has a short title and a list of turns. Each turn is one speaker's spoken line.",
    "",
    "Return JSON with this exact shape:",
    `{
  "title": "string — a catchy episode title",
  "sections": [
    {
      "id": "kebab-case-id",
      "title": "string",
      "turns": [
        { "speakerKey": "host", "text": "spoken line..." }
      ]
    }
  ]
}`,
  ]
    .filter(Boolean)
    .join("\n");

  return [
    { role: "system" as const, content: system },
    { role: "user" as const, content: user },
  ];
}

export function buildSectionMessages(
  config: EpisodeConfig,
  script: StructuredScript,
  sectionId: string
) {
  const section = script.sections.find((s) => s.id === sectionId);
  const speakerList = config.speakers.map((s) => `"${s.speakerKey}"=${s.displayName}`).join(", ");

  const system =
    "You are an expert podcast scriptwriter. Rewrite a single section of an existing episode, keeping the same speakers, tone, and language. Return STRICT JSON for just that one section.";

  const user = [
    `Episode title: ${script.title}`,
    `Tone: ${config.tone}. Language: ${config.language}. Speakers: ${speakerList}.`,
    "",
    `Rewrite the section titled "${section?.title ?? sectionId}" (id "${sectionId}") to be fresh and engaging while serving the same purpose in the episode.`,
    "",
    "Return JSON with this exact shape:",
    `{ "id": "${sectionId}", "title": "string", "turns": [ { "speakerKey": "host", "text": "..." } ] }`,
  ].join("\n");

  return [
    { role: "system" as const, content: system },
    { role: "user" as const, content: user },
  ];
}