/* =======================================================================
   File: static/js/log_view.js
   Purpose:
       High-performance rolling log viewer
       - efficient delta polling
       - append-only mode (no DOM reset)
       - rolling limit (prevents memory freeze)
       - supports both global logs and per-book logs
   ======================================================================= */

console.log(">>> log_view.js LOADING…");

/* ---------------------------------------------------------
   Global log viewer state
   --------------------------------------------------------- */
let LOG_FILTER = "ALL";
let LAST_LOG_INDEX = -1; // delta offset
const MAX_LOG_LINES = 600;

/* ---------------------------------------------------------
   Apply filter on existing log lines
   --------------------------------------------------------- */
function applyLogFilter() {
  const lines = $$(".log-line");
  lines.forEach((line) => {
    const text = line.innerText;
    const show = LOG_FILTER === "ALL" || (text && text.includes(LOG_FILTER));
    line.style.display = show ? "block" : "none";
  });
}

/* ---------------------------------------------------------
   DOM Ready — bind clear/filter
   --------------------------------------------------------- */
document.addEventListener("DOMContentLoaded", () => {
  console.log(">>> log_view.js DOMContentLoaded");

  const clearBtn = $("#log-clear");
  const output = $("#log-output");

  if (!output) {
    console.log(">>> log_view.js: No #log-output → viewer disabled");
    return;
  }

  if (clearBtn) {
    clearBtn.addEventListener("click", () => {
      console.log(">>> log_view.js: Clear log viewer");
      output.innerHTML = "";
      LAST_LOG_INDEX = -1;
    });
  }
});

/* ---------------------------------------------------------
   Append ONE line
   --------------------------------------------------------- */
function rollingAppend(lineText) {
  const output = $("#log-output");
  if (!output) return;

  const div = document.createElement("div");
  div.classList.add("log-line");

  // Type detection
  if (lineText.includes("[DL]") || lineText.includes("[DOWNLOAD]"))
    div.classList.add("dl");
  else if (lineText.includes("[PARSE]")) div.classList.add("parse");
  else if (lineText.includes("[SAVE]")) div.classList.add("save");
  else if (lineText.includes("[AUDIO]")) div.classList.add("audio");
  else if (lineText.includes("[CTRL]")) div.classList.add("ctrl");
  else if (lineText.includes("[ERROR]")) div.classList.add("error");
  else div.classList.add("default");

  div.textContent = lineText;
  output.appendChild(div);

  // Rolling limit
  while (output.childNodes.length > MAX_LOG_LINES) {
    output.removeChild(output.firstChild);
  }
}

/* ---------------------------------------------------------
   Primary entry: updateLogs()
   Accepts:
     { logs:[...], last:N }
     OR legacy:
     { lines:[...], last:N }
   --------------------------------------------------------- */
function updateLogs(packet) {
  const output = $("#log-output");
  if (!output || !packet) return;

  let lines = packet.logs || packet.lines || [];
  if (!Array.isArray(lines)) return;

  lines.forEach((line) => rollingAppend(line));

  // Correct unified delta index handling
  if (packet.last !== undefined) {
    LAST_LOG_INDEX = packet.last;
  }

  applyLogFilter();
  autoScroll(output);
}

/* ---------------------------------------------------------
   Delta polling — global logs ONLY
   (dashboard.js overrides logs per-book)
   --------------------------------------------------------- */
function pollLogs() {
  fetch(`/logs?last_index=${LAST_LOG_INDEX}`)
    .then((r) => r.json())
    .then((data) => {
      const lines = data.lines || [];
      if (lines.length > 0) {
        lines.forEach((line) => rollingAppend(line));
        LAST_LOG_INDEX = data.last;
      }
    })
    .catch((err) => {
      console.warn(">>> log_view.js pollLogs() error:", err);
    });
}

setInterval(pollLogs, 2800);

console.log(">>> log_view.js LOADED");