// 状态栏渲染器
// 忠实移植 CCometixLine StatusLineGenerator：段渲染 + Powerline 箭头分隔符颜色过渡

import { truncateToWidth } from "@earendil-works/pi-tui";
import type { AnsiColor, Config, SegmentConfig, SegmentData } from "./types.ts";
import { bgSeq, colorText, fgSeq } from "./ansi.ts";

/** 取段图标（dynamic_icon 优先，否则按 style.mode 选择） */
function getIcon(config: Config, seg: SegmentConfig, data: SegmentData): string {
  if (data.metadata["dynamic_icon"]) return data.metadata["dynamic_icon"];
  return config.style.mode === "plain" ? seg.icon.plain : seg.icon.nerdFont;
}

/**
 * 渲染单个段（忠实移植 CCometixLine render_segment）
 * - 有背景色：去中间 reset，整体包背景，末尾恢复默认背景
 * - 无背景色：图标 + 文本各自包裹并 reset
 */
function renderSegment(config: Config, seg: SegmentConfig, data: SegmentData): string {
  const icon = getIcon(config, seg, data);
  const bold = seg.styles.textBold;

  if (seg.colors.background) {
    const bg = bgSeq(seg.colors.background);
    // 去除中间 reset，保留颜色序列，避免破坏背景连续性
    const iconColored = colorText(icon, seg.colors.icon, false).replace(/\x1b\[0m/g, "");
    const textStyled = colorText(data.primary, seg.colors.text, bold).replace(/\x1b\[0m/g, "");
    let content = ` ${iconColored} ${textStyled} `;
    if (data.secondary) {
      const sec = colorText(data.secondary, seg.colors.text, bold).replace(/\x1b\[0m/g, "");
      content += `${sec} `;
    }
    return `${bg}${content}\x1b[49m`; // \x1b[49m = 默认背景
  }

  // 无背景色
  const iconColored = colorText(icon, seg.colors.icon, false);
  const textStyled = colorText(data.primary, seg.colors.text, bold);
  let s = `${iconColored} ${textStyled}`;
  if (data.secondary) {
    s += ` ${colorText(data.secondary, seg.colors.text, bold)}`;
  }
  return s;
}

/** Powerline 箭头分隔符（前景=上一段背景，背景=下一段背景，实现颜色过渡） */
function powerlineArrow(prevBg?: AnsiColor, currBg?: AnsiColor): string {
  const arrow = "\ue0b0";
  if (prevBg && currBg) return `${bgSeq(currBg)}${fgSeq(prevBg)}${arrow}\x1b[0m`;
  if (prevBg) return `${fgSeq(prevBg)}${arrow}\x1b[0m`;
  if (currBg) return `${bgSeq(currBg)}${arrow}\x1b[0m`;
  return arrow;
}

/**
 * 生成完整状态栏单行（移植 CCometixLine generate）
 * - separator 为 powerline 箭头 \ue0b0 时，使用颜色过渡箭头
 * - 否则使用白色分隔符
 */
export function generateStatusLine(
  config: Config,
  segments: { seg: SegmentConfig; data: SegmentData }[],
): string {
  const enabled = segments.filter((s) => s.seg.enabled);
  const rendered = enabled
    .map((s) => renderSegment(config, s.seg, s.data))
    .filter((s) => s.length > 0);
  if (rendered.length === 0) return "";

  let joined: string;
  if (config.style.separator === "\ue0b0") {
    // Powerline 箭头：按相邻段背景色过渡
    let result = rendered[0]!;
    for (let i = 1; i < rendered.length; i++) {
      const prevBg = enabled[i - 1]?.seg.colors.background;
      const currBg = enabled[i]?.seg.colors.background;
      result += powerlineArrow(prevBg, currBg) + rendered[i]!;
    }
    result += "\x1b[0m";
    joined = result;
  } else {
    const sep = `\x1b[37m${config.style.separator}\x1b[0m`; // 白色分隔符
    joined = rendered.join(sep);
  }
  return joined;
}

/** 渲染 footer 单行：生成状态栏并按宽度截断 */
export function renderFooterLine(
  config: Config,
  segments: { seg: SegmentConfig; data: SegmentData }[],
  width: number,
): string[] {
  const line = generateStatusLine(config, segments);
  if (!line) return [];
  return [truncateToWidth(line, width)];
}