xiaoxia-saas/packages/domain/ass_subtitle_builder.py

"""ASS 字幕构建领域模型 — 纯逻辑，无文件IO依赖.

抽离自 render_subtitles.py，包含：
- 颜色转换（hex → ASS &HBBGGRR）
- 位置对齐映射
- ASS Style 行构建
- 文本转义
- 时间格式化
- 完整 ASS 内容生成（返回字符串，不写文件）
"""

from __future__ import annotations

import logging
from typing import Any

logger = logging.getLogger(__name__)


# ── 常量 ──────────────────────────────────────────────────────────────────────

# Title/Subtitle 默认边距（像素）
TITLE_MARGIN_TOP = 60
TITLE_MARGIN_BOTTOM = 60
TITLE_MARGIN_SIDE = 40


# ── 颜色转换 ──────────────────────────────────────────────────────────────────


def hex_to_ass_color(hex_color: str) -> str:
    """将 HEX 颜色（#RRGGBB）转换为 ASS &HBBGGRR 格式.

    Args:
        hex_color: HEX 颜色字符串，支持 #RRGGBB 或 RRGGBB 格式

    Returns:
        ASS 格式颜色，如 &H0000FF（红色）
    """
    hex_color = hex_color.lstrip("#")
    if len(hex_color) != 6:
        return "&H000000"
    r, g, b = hex_color[0:2], hex_color[2:4], hex_color[4:6]
    return f"&H{b.upper()}{g.upper()}{r.upper()}"


# ── 位置对齐 ──────────────────────────────────────────────────────────────────


def position_to_ass_alignment(position: str) -> int:
    """将文字位置映射为 ASS \\an 对齐编号.

    ASS 对齐编号（数字小键盘布局）：
      7 8 9
      4 5 6
      1 2 3

    Args:
        position: 位置字符串 top/center/bottom

    Returns:
        ASS 对齐编号，默认 8（顶部居中）
    """
    mapping = {
        "top": 8,
        "center": 5,
        "bottom": 2,
    }
    return mapping.get(position, 8)


# ── Style 行构建 ──────────────────────────────────────────────────────────────


def build_ass_style(
    style_name: str,
    *,
    font_name: str = "思源黑体",
    font_size: int = 48,
    primary_color: str = "&H00FFFFFF",
    outline_color: str = "&H00000000",
    outline_width: float = 1.0,
    shadow_blur: float = 0.0,
    shadow_offset: tuple[int, int] = (0, 0),
    bold: bool = False,
    italic: bool = False,
    alignment: int = 8,
    margin_v: int = 60,
    margin_l: int = 40,
    margin_r: int = 40,
) -> str:
    """构建 ASS Style 行.

    Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour,
            Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle,
            BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

    Args:
        style_name: 样式名称
        font_name: 字体名称
        font_size: 字体大小
        primary_color: 主色（文字颜色）
        outline_color: 描边颜色
        outline_width: 描边宽度
        shadow_blur: 阴影模糊度（>0 时启用阴影）
        shadow_offset: 阴影偏移 (x, y)
        bold: 是否粗体
        italic: 是否斜体
        alignment: 对齐方式（ASS \an 编号）
        margin_v: 垂直边距
        margin_l: 左边距
        margin_r: 右边距

    Returns:
        完整的 Style: 行字符串
    """
    bold_val = -1 if bold else 0
    italic_val = -1 if italic else 0

    # BackColour 用于阴影（BorderStyle=1 时 outline + shadow）
    back_color = primary_color

    # Shadow 深度：shadow_offset[1] 作为纵向偏移
    shadow_depth = shadow_offset[1] if shadow_blur > 0 else 0

    return (
        f"Style: {style_name},{font_name},{font_size},{primary_color},"
        f"&H000000FF,{outline_color},{back_color},"
        f"{bold_val},{italic_val},0,0,100,100,0,0,"
        f"1,{outline_width},{shadow_depth},{alignment},"
        f"{margin_l},{margin_r},{margin_v},1"
    )


# ── 文本转义 ──────────────────────────────────────────────────────────────────


def escape_ass_text(text: str) -> str:
    r"""转义 ASS 文本中的特殊字符.

    ASS 中换行用 \N（硬换行）或 \n（软换行），
    大括号 {} 用于覆盖样式，需要转义.

    Args:
        text: 原始文本

    Returns:
        转义后的 ASS 文本
    """
    # 将实际换行转为 ASS 硬换行
    text = text.replace("\r\n", "\\N").replace("\n", "\\N").replace("\r", "\\N")
    # 转义大括号（ASS 用它做样式覆盖标签）
    text = text.replace("{", "(").replace("}", ")")
    return text


# ── 时间格式化 ────────────────────────────────────────────────────────────────


def format_ass_time(seconds: float) -> str:
    """将秒数格式化为 ASS 时间格式 H:MM:SS.cc.

    Args:
        seconds: 秒数

    Returns:
        ASS 格式时间，如 "1:23:45.67"
    """
    hours = int(seconds // 3600)
    minutes = int((seconds % 3600) // 60)
    secs = seconds % 60
    return f"{hours}:{minutes:02d}:{secs:05.2f}"


# ── 完整 ASS 内容生成 ─────────────────────────────────────────────────────────



def _wrap_title_text(
    text: str,
    video_width: int,
    font_size: int,
    margin_l: int = TITLE_MARGIN_SIDE,
    margin_r: int = TITLE_MARGIN_SIDE,
) -> str:
    """根据视频宽度和字号自动换行标题文本。

    中文字符按 font_size 像素宽度估算，英文/数字按半角估算。
    超过可用宽度时插入 \\N (ASS 硬换行)。
    """
    if not text or video_width <= 0 or font_size <= 0:
        return text

    available_width = video_width - margin_l - margin_r
    if available_width <= 0:
        return text

    lines: list[str] = []
    current_line = ""
    current_width = 0.0

    for ch in text:
        # CJK 字符按全角估算，其他按半角
        char_width = float(font_size) if ord(ch) > 0x2E80 else font_size * 0.55

        if current_width + char_width > available_width and current_line:
            lines.append(current_line)
            current_line = ch
            current_width = char_width
        else:
            current_line += ch
            current_width += char_width

    if current_line:
        lines.append(current_line)

    return "\\N".join(lines)


def build_ass_content(
    *,
    video_width: int,
    video_height: int,
    video_duration: float,
    title_text: str = "",
    title_config: dict[str, Any] | None = None,
    subtitle_text: str = "",
    subtitle_config: dict[str, Any] | None = None,
) -> str:
    """生成 ASS 字幕文件内容（纯字符串，不写文件）.

    支持 Title（标题）和 Subtitle（字幕）两种字幕类型，
    各自可独立配置样式、位置和内容.

    Args:
        video_width: 视频宽度（用于 ASS PlayResX）
        video_height: 视频高度（用于 ASS PlayResY）
        video_duration: 视频总时长（秒），字幕显示整个时长
        title_text: 标题文本
        title_config: 标题样式配置
        subtitle_text: 字幕文本
        subtitle_config: 字幕样式配置

    Returns:
        完整的 ASS 文件内容字符串；无字幕时返回空字符串
    """
    title_config = title_config or {}
    subtitle_config = subtitle_config or {}

    # ── 兼容前端简化格式：stroke/shadow 为 boolean 时，转换为标准 dict ──
    # 前端 TitleSettings 发送 stroke=true/false, shadow=true/false
    # 后端 build_ass_style 期望 stroke={enabled, color, width}, shadow={enabled, blur, offset_x, offset_y}
    if title_config:
        _stroke_val = title_config.get("stroke")
        if isinstance(_stroke_val, bool):
            title_config["stroke"] = {
                "enabled": _stroke_val,
                "color": "#000000",
                "width": 2,
            } if _stroke_val else {"enabled": False}
        _shadow_val = title_config.get("shadow")
        if isinstance(_shadow_val, bool):
            title_config["shadow"] = {
                "enabled": _shadow_val,
                "color": "#000000",
                "blur": 4,
                "offset_x": 2,
                "offset_y": 2,
            } if _shadow_val else {"enabled": False}

    title_enabled = title_config.get("enabled", True) and bool(title_text.strip())
    subtitle_enabled = subtitle_config.get("enabled", True) and bool(subtitle_text.strip())

    if not title_enabled and not subtitle_enabled:
        return ""

    styles: list[str] = []
    events: list[str] = []

    # ── Title 样式与事件 ──────────────────────────────────────────────────
    if title_enabled:
        title_color = hex_to_ass_color(title_config.get("color", "#ffffff"))
        title_stroke = title_config.get("stroke", {}) or {}
        title_shadow = title_config.get("shadow", {}) or {}
        stroke_color = hex_to_ass_color(title_stroke.get("color", "#000000"))
        stroke_width = float(title_stroke.get("width", 2)) if title_stroke.get("enabled", False) else 0.0
        shadow_blur = float(title_shadow.get("blur", 4)) if title_shadow.get("enabled", False) else 0.0
        shadow_offset = (
            title_shadow.get("offset_x", 2) if title_shadow.get("enabled", False) else 0,
            title_shadow.get("offset_y", 2) if title_shadow.get("enabled", False) else 0,
        )

        title_alignment = position_to_ass_alignment(title_config.get("position", "top"))

        styles.append(
            build_ass_style(
                "TitleStyle",
                font_name=title_config.get("font", "思源黑体"),
                font_size=min(int(title_config.get("size", 36)), 36),
                primary_color=title_color,
                outline_color=stroke_color,
                outline_width=stroke_width,
                shadow_blur=shadow_blur,
                shadow_offset=shadow_offset,
                bold=bool(title_config.get("bold", True)),
                italic=bool(title_config.get("italic", False)),
                alignment=title_alignment,
                margin_v=TITLE_MARGIN_TOP,
                margin_l=TITLE_MARGIN_SIDE,
                margin_r=TITLE_MARGIN_SIDE,
            )
        )

        # 根据视频宽度和字号自动换行标题，防止超出画面
        # 先 escape 特殊字符，再插入换行符 \N，避免顺序颠倒导致 \N 被转义
        title_font_size = min(int(title_config.get("size", 36)), 36)
        safe_title_text_raw = escape_ass_text(title_text)
        safe_title_text = _wrap_title_text(safe_title_text_raw, video_width, title_font_size)

        events.append(
            "Dialogue: 0,0:00:00.00," f"{format_ass_time(video_duration)}," "TitleStyle,,0,0,0,," f"{safe_title_text}"
        )

    # ── Subtitle 样式与事件 ───────────────────────────────────────────────
    if subtitle_enabled:
        sub_color = hex_to_ass_color(subtitle_config.get("color", "#ffffff"))
        sub_alignment = position_to_ass_alignment(subtitle_config.get("position", "bottom"))

        styles.append(
            build_ass_style(
                "SubtitleStyle",
                font_name=subtitle_config.get("font", "思源黑体"),
                font_size=int(subtitle_config.get("size", 24)),
                primary_color=sub_color,
                outline_color="&H00000000",
                outline_width=1.0,
                shadow_blur=0.0,
                shadow_offset=(0, 0),
                bold=False,
                italic=False,
                alignment=sub_alignment,
                margin_v=TITLE_MARGIN_BOTTOM,
                margin_l=TITLE_MARGIN_SIDE,
                margin_r=TITLE_MARGIN_SIDE,
            )
        )

        safe_subtitle_text = escape_ass_text(subtitle_text)

        events.append(
            "Dialogue: 0,0:00:00.00,"
            f"{format_ass_time(video_duration)},"
            "SubtitleStyle,,0,0,0,,"
            f"{safe_subtitle_text}"
        )

    # ── 组装 ASS 文件 ─────────────────────────────────────────────────────
    return f"""[Script Info]
ScriptType: v4.00+
PlayResX: {video_width}
PlayResY: {video_height}
ScaledBorderAndShadow: yes
WrapStyle: 2
Encoding: UTF-8

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding  # noqa: E501
{chr(10).join(styles)}

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
{chr(10).join(events)}
"""