const DEFAULT_TASKS = [
  {
    id: "task-fit-summary",
    name: "Fit Summary",
    text:
      "Summarize the role, highlight key requirements, and assess my fit using the resume. Note any gaps and what to emphasize."
  }
];

const DEFAULT_SETTINGS = {
  apiKey: "",
  model: "gpt-4o-mini",
  systemPrompt:
    "You are a precise, honest assistant. Be concise, highlight uncertainties, and avoid inventing details.",
  resume: "",
  tasks: DEFAULT_TASKS
};

chrome.runtime.onInstalled.addListener(async () => {
  const stored = await chrome.storage.local.get(Object.keys(DEFAULT_SETTINGS));
  const updates = {};

  for (const [key, value] of Object.entries(DEFAULT_SETTINGS)) {
    const existing = stored[key];
    const missing =
      existing === undefined ||
      existing === null ||
      (key === "tasks" && !Array.isArray(existing));

    if (missing) updates[key] = value;
  }

  if (Object.keys(updates).length) {
    await chrome.storage.local.set(updates);
  }
});

chrome.runtime.onConnect.addListener((port) => {
  if (port.name !== "analysis") return;

  let abortController = null;

  const resetAbort = () => {
    if (abortController) abortController.abort();
    abortController = null;
  };

  port.onMessage.addListener((message) => {
    if (message?.type === "START_ANALYSIS") {
      resetAbort();
      abortController = new AbortController();
      void handleAnalysisRequest(port, message.payload, abortController.signal).catch(
        (error) => {
          if (error?.name === "AbortError") {
            port.postMessage({ type: "ABORTED" });
            return;
          }
          port.postMessage({
            type: "ERROR",
            message: error?.message || "Unknown error during analysis."
          });
        }
      );
      return;
    }

    if (message?.type === "ABORT_ANALYSIS") {
      resetAbort();
    }
  });

  port.onDisconnect.addListener(() => {
    resetAbort();
  });
});

function buildUserMessage(resume, task, posting) {
  return [
    "=== RESUME ===",
    resume || "",
    "",
    "=== TASK ===",
    task || "",
    "",
    "=== JOB POSTING ===",
    posting || ""
  ].join("\n");
}

async function handleAnalysisRequest(port, payload, signal) {
  const { apiKey, model, systemPrompt, resume, taskText, postingText } = payload || {};

  if (!apiKey) {
    port.postMessage({ type: "ERROR", message: "Missing OpenAI API key." });
    return;
  }

  if (!model) {
    port.postMessage({ type: "ERROR", message: "Missing model name." });
    return;
  }

  if (!postingText) {
    port.postMessage({ type: "ERROR", message: "No job posting text provided." });
    return;
  }

  if (!taskText) {
    port.postMessage({ type: "ERROR", message: "No task prompt selected." });
    return;
  }

  const userMessage = buildUserMessage(resume, taskText, postingText);

  await streamChatCompletion({
    apiKey,
    model,
    systemPrompt: systemPrompt || "",
    userMessage,
    signal,
    onDelta: (text) => port.postMessage({ type: "DELTA", text })
  });

  port.postMessage({ type: "DONE" });
}

async function streamChatCompletion({
  apiKey,
  model,
  systemPrompt,
  userMessage,
  signal,
  onDelta
}) {
  const response = await fetch("https://api.openai.com/v1/chat/completions", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${apiKey}`
    },
    body: JSON.stringify({
      model,
      stream: true,
      messages: [
        { role: "system", content: systemPrompt },
        { role: "user", content: userMessage }
      ]
    }),
    signal
  });

  if (!response.ok) {
    const errorText = await response.text();
    throw new Error(`OpenAI API error ${response.status}: ${errorText}`);
  }

  const reader = response.body.getReader();
  const decoder = new TextDecoder();
  let buffer = "";

  // OpenAI streams Server-Sent Events; parse incremental deltas from data lines.
  while (true) {
    const { value, done } = await reader.read();
    if (done) break;

    buffer += decoder.decode(value, { stream: true });
    const lines = buffer.split("\n");
    buffer = lines.pop() || "";

    for (const line of lines) {
      const trimmed = line.trim();
      if (!trimmed.startsWith("data:")) continue;

      const data = trimmed.slice(5).trim();
      if (!data) continue;
      if (data === "[DONE]") return;

      let parsed;
      try {
        parsed = JSON.parse(data);
      } catch {
        continue;
      }

      const delta = parsed?.choices?.[0]?.delta?.content;
      if (delta) onDelta(delta);
    }
  }
}