import { imageSource } from "./attachments";
import { renderInlineContent, renderModelOutput } from "./render";
import { describeActivity } from "./thread";
import type { Attachment, ChatTurn, ThreadMessage, ToolCallRecord } from "./types";

/**
 * Markdown rendering for the detail panel.
 *
 * Kept as pure functions so the transcript layout can be tested without
 * mounting a component.
 *
 * ## Emphasis
 *
 * Nothing here is bold except an error. The answer is what is being read, so it
 * is plain body text and carries no label. The question is a blockquote, which
 * the renderer draws dimmed, italic, and with a left rule. Putting a `**You**`
 * and a `**Lam**` header on each exchange gave both speakers the same visual
 * weight and made the reader scan past chrome to reach the answer.
 *
 * Raycast solves the same problem by aligning messages: right-aligned bubbles
 * for the user. Markdown offers no alignment control, so styling is the only
 * lever available.
 */

export const STREAMING_CURSOR = "▍";

/**
 * Renders attachments as markdown images.
 *
 * Vicinae does resolve a local file: `MdImage.qml` draws it block-level and
 * centred, uses the alt text as an italic caption underneath, and caps the
 * height at 200px no matter what is asked for. So this is a thumbnail rather
 * than something readable, which is why the action panel also offers Open
 * Screenshot for the full image.
 *
 * The alt text is short on purpose. Whatever is here is drawn centred under the
 * image, so a sentence reads as a stray line of prose floating in the middle of
 * the pane. It is also the only thing left if the file has since been deleted,
 * which is why it is not empty.
 */
export function renderAttachments(attachments: Attachment[]): string {
  return attachments.map((attachment) => `![Screenshot](${imageSource(attachment)})`).join("\n\n");
}

/** Which optional sections the transcript includes. Driven by preferences. */
export interface TranscriptOptions {
  showToolCalls: boolean;
  showReasoning: boolean;
}

const SHOW_EVERYTHING: TranscriptOptions = { showToolCalls: true, showReasoning: true };

/** Prefixes every line so a multi-line message stays one continuous quote block. */
export function quote(text: string): string {
  return text
    .split("\n")
    .map((line) => `> ${line}`.trimEnd())
    .join("\n");
}

/** How many calls failed for a reason other than being refused as a repeat. */
function countFailures(calls: ToolCallRecord[]): number {
  // A refused repeat is an `isError` too, but it did not fail: it is the loop
  // guard noticing a rut, which is a different thing and is said differently.
  return calls.filter((call) => call.isError && !call.repeated).length;
}

/** Whether the turn was cut short because a call kept repeating itself. */
function wasStopped(calls: ToolCallRecord[]): boolean {
  return calls.some((call) => call.repeated);
}

/**
 * One italic line naming the tools a turn used, each mentioned once.
 *
 * Listing every call in order said nothing a name does not, and on a research
 * turn it said it twenty times: `_Tools: web_search, web_search, web_search,
 * web_fetch (failed), web_search…_` ran to three lines of the same two words.
 * Names in order of first use, then a count of what went wrong, which is the
 * only part of that repetition that carries information.
 */
function renderTools(message: ThreadMessage): string {
  const names: string[] = [];
  for (const call of message.toolCalls) {
    if (!names.includes(call.name)) names.push(call.name);
  }

  const listed = names.map((name) => `\`${name}\``).join(", ");
  const failed = countFailures(message.toolCalls);

  const notes: string[] = [];
  if (failed > 0) notes.push(`${failed} failed`);
  if (wasStopped(message.toolCalls)) notes.push("stopped: the same call kept repeating");

  const suffix = notes.length > 0 ? ` (${notes.join(", ")})` : "";
  return `_Tools: ${listed}${suffix}_`;
}

/**
 * The one line shown when tool calls are hidden but something went wrong.
 *
 * Hiding the list is the user's choice, and a list of names is what they turned
 * off. A turn where a call failed or was refused as a repeat is different: the
 * answer alone would not account for it, so it is said in a sentence rather than
 * dropped, and the names stay hidden.
 */
function renderToolFailureNote(message: ThreadMessage): string | undefined {
  const failed = countFailures(message.toolCalls);
  const stopped = wasStopped(message.toolCalls);
  if (failed === 0 && !stopped) return undefined;

  const parts: string[] = [];
  if (failed > 0) parts.push(`${failed} tool call${failed === 1 ? "" : "s"} failed`);
  if (stopped) parts.push("a call kept repeating, so the turn was cut short");

  return `_${parts.join(" and ")}._`;
}

function renderMessage(message: ThreadMessage, options: TranscriptOptions): string {
  // The question is identified by its styling alone. It goes through the same
  // rendering pass as an answer, because a person pastes LaTeX into a question
  // as readily as a model writes it, and a question full of raw HTML should be
  // put behind the same fence.
  if (message.role === "user") {
    const images = renderAttachments(message.attachments);
    const asked = quote(renderInlineContent(message.text));

    return images ? `${asked}\n\n${images}` : asked;
  }

  const thinking = message.thinking.trim();
  /**
   * Live reasoning is shown while a turn is in flight whether or not the
   * preference is on: it is the only sign of progress when a model is thinking
   * rather than writing, and waiting on a spinner is worse than reading the
   * thought. Once the turn ends it stays only if the user asked for it, so
   * `Show Reasoning` still governs the finished transcript.
   */
  const liveThinking = message.isStreaming && thinking.length > 0;
  /** The stored trace, kept as an appendix under the answer it produced. */
  const storedThinking = !message.isStreaming && options.showReasoning && thinking.length > 0;
  const showThinking = liveThinking || storedThinking;

  // While a tool is running there is no answer text yet, so the activity line
  // stands in and the user can see what Lam is actually doing. It is shown
  // whether or not tokens have arrived, because a tool that starts after the
  // answer has begun would otherwise be invisible for the rest of the turn.
  const activityLine =
    message.isStreaming && message.activity ? `_${describeActivity(message.activity)}…_` : undefined;

  /** The answer, or whatever stands in for it while there is none. */
  const answered = message.text.trim();
  const body = answered
    ? // One pass, in one place: fences get their languages and links recovered,
      // then TeX becomes something drawable and the HTML around it is filtered to
      // the subset the renderer acts on. See `render.ts` for the order and why.
      renderModelOutput(answered).text
    : !message.isStreaming
      ? "_No response._"
      : activityLine
        ? // The activity line above is already saying what is being waited on, so
          // printing the placeholder as well put the same sentence on screen
          // twice: once as a note above the transcript and once as the stand-in.
          undefined
        : liveThinking
          ? // The reasoning below is already saying the model is working, so
            // "Thinking…" on top of it would only repeat it.
            undefined
          : message.status
            ? `_${message.status}…_`
            : "_Thinking…_";

  const sections: string[] = [];
  const activityIndex = activityLine ? sections.push(activityLine) - 1 : -1;
  const bodyIndex = body ? sections.push(body) - 1 : -1;

  // The one thing allowed to break the plain-text rule, because it means
  // something went wrong and should not be skimmed past.
  if (message.error) sections.push("", `**Error:** ${message.error}`);

  /**
   * Tool calls are a display preference. When they are on, every tool is named
   * once. When they are off, nothing is listed; a failure or a refused repeat
   * still gets one quiet sentence, because those are the cases where hiding the
   * line would leave the user with an answer they cannot account for.
   */
  if (options.showToolCalls && message.toolCalls.length > 0) {
    sections.push("", renderTools(message));
  } else if (!options.showToolCalls) {
    const note = renderToolFailureNote(message);
    if (note) sections.push("", note);
  }

  if (showThinking) {
    // Only live reasoning can be the first thing in a message, so the blank
    // separator is conditional: otherwise the transcript opens on an empty line.
    if (sections.length > 0) sections.push("");
    sections.push("_Reasoning_", "", quote(thinking));
  }

  /**
   * The cursor marks what is arriving. The answer wins when there is one, then
   * the live reasoning, and only then the activity line: reasoning on screen
   * means the model is thinking, which is newer than the tool it called to get
   * there. It is placed before the quiet sections so it never lands on a tool
   * list or an appendix.
   */
  if (message.isStreaming) {
    const reasoningIndex = showThinking && liveThinking ? sections.length - 1 : -1;
    const target = bodyIndex >= 0 ? bodyIndex : reasoningIndex >= 0 ? reasoningIndex : activityIndex;
    if (target >= 0) sections[target] = `${sections[target]} ${STREAMING_CURSOR}`;
  }

  return sections.join("\n");
}

/**
 * Renders the whole conversation, newest message first.
 *
 * The detail panel shows the entire thread rather than just one message on
 * purpose. Vicinae's list resets its selection to the first row whenever the
 * model changes, and streaming changes it on every flush, so the selected row
 * is not something the extension can rely on staying put while an answer
 * arrives. Showing the whole thread means the live answer is always on screen.
 *
 * Messages are grouped back into exchanges for layout: an answer and the
 * question it responds to belong to the same block, so the horizontal rule only
 * separates one exchange from the next rather than dividing every single
 * message. That rule earns its place with newest-first ordering, where the
 * boundary between two answers would otherwise be easy to miss.
 */
export function buildThreadMarkdown(
  messages: ThreadMessage[],
  options: TranscriptOptions = SHOW_EVERYTHING,
): string {
  if (messages.length === 0) return "";

  const blocks: string[] = [];
  let currentTurn = "";
  let buffer: string[] = [];

  const flush = () => {
    if (buffer.length > 0) blocks.push(buffer.join("\n\n"));
    buffer = [];
  };

  for (const message of messages) {
    // `turnId:role`, so the turn is the id without its role suffix.
    const turnId = message.id.replace(/:(assistant|user)$/, "");
    if (turnId !== currentTurn) {
      flush();
      currentTurn = turnId;
    }
    buffer.push(renderMessage(message, options));
  }

  flush();
  return blocks.join("\n\n---\n\n");
}

/**
 * Flattens a whole conversation into plain text for the clipboard.
 *
 * Unlike the transcript this reads oldest-first: as a standalone document, a
 * conversation is easier to read in the order it happened.
 *
 * This needs labels because the transcript's styling (blockquotes and dimmed
 * text) is gone by the time it reaches a clipboard.
 */
export function sessionToPlainText(turns: ChatTurn[]): string {
  if (turns.length === 0) return "";

  return turns
    .map((turn) => {
      const question = `**You**\n\n${turn.prompt}`;
      const attached = turn.attachments.length > 0 ? "\n\n_(screenshot attached)_" : "";
      const answer = turn.response.trim() || (turn.error ? "" : "_(no response)_");
      const failure = turn.error ? `\n\n**[error]** ${turn.error}` : "";
      return `${question}${attached}\n\n**Lam**\n\n${answer}${failure}`;
    })
    .join("\n\n---\n\n");
}