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server-rs/crates/api-server/src/prompt/puzzle/image.rs

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+/// 拼图图片生成的默认反向提示词。
+///
+/// 这里单独收口拼图图片提示词，避免图片生成链路、候选图持久化和 DashScope 请求编排
+/// 混在同一个脚本里，后续调画风或资产约束时只需要改这一处。
+pub(crate) const PUZZLE_DEFAULT_NEGATIVE_PROMPT: &str =
+    "低清晰度，低质量，文字水印，畸形构图，过度模糊，重复肢体，画面脏污";
+
+/// wan2.2 / wan2.1 文生图旧协议的正向 prompt 上限。
+///
+/// 中文注释：DashScope 旧 text2image 接口会把超长 prompt 判成请求参数不合法，
+/// 所以这里先在拼图提示词模块内压缩，保证固定玩法约束不会被用户长描述挤掉。
+pub(crate) const PUZZLE_TEXT_TO_IMAGE_PROMPT_MAX_CHARS: usize = 500;
+
+const PUZZLE_IMAGE_LEVEL_NAME_MAX_CHARS: usize = 40;
+const PUZZLE_IMAGE_PROMPT_FALLBACK: &str = "清晰、有辨识度的拼图画面";
+
+/// 根据拼图关卡名和陶泥主输入构造最终发给图片模型的提示词。
+pub(crate) fn build_puzzle_image_prompt(level_name: &str, prompt: &str) -> String {
+    let level_name =
+        truncate_puzzle_prompt_segment(level_name.trim(), PUZZLE_IMAGE_LEVEL_NAME_MAX_CHARS);
+    let prompt = prompt.trim();
+    let prompt = if prompt.is_empty() {
+        PUZZLE_IMAGE_PROMPT_FALLBACK
+    } else {
+        prompt
+    };
+    let template_chars = build_puzzle_image_prompt_text(level_name.as_str(), "")
+        .chars()
+        .count();
+    let prompt_max_chars = PUZZLE_TEXT_TO_IMAGE_PROMPT_MAX_CHARS.saturating_sub(template_chars);
+    let prompt = truncate_puzzle_prompt_segment(prompt, prompt_max_chars);
+    let image_prompt = build_puzzle_image_prompt_text(level_name.as_str(), prompt.as_str());
+
+    debug_assert!(
+        image_prompt.chars().count() <= PUZZLE_TEXT_TO_IMAGE_PROMPT_MAX_CHARS,
+        "puzzle image prompt should fit DashScope wan2.2 limit"
+    );
+    image_prompt
+}
+
+fn build_puzzle_image_prompt_text(level_name: &str, prompt: &str) -> String {
+    format!(
+        concat!(
+            "请生成一张高清插画。",
+            "关卡名：{level_name}。",
+            "画面主体：{prompt}。",
+            "画面要求：1:1 正方形拼图关卡，适配 3x3 或 4x4 拼图切块，",
+            "主体要清晰集中，前中后景层次明确，局部细节丰富但不要杂乱，",
+            "避免文字、水印、边框和 UI 元素。"
+        ),
+        level_name = level_name,
+        prompt = prompt,
+    )
+}
+
+fn truncate_puzzle_prompt_segment(value: &str, max_chars: usize) -> String {
+    if value.chars().count() <= max_chars {
+        return value.to_string();
+    }
+
+    const MARKER: &str = "...";
+    if max_chars <= MARKER.chars().count() {
+        return value.chars().take(max_chars).collect();
+    }
+
+    let keep_chars = max_chars - MARKER.chars().count();
+    format!(
+        "{}{MARKER}",
+        value.chars().take(keep_chars).collect::<String>()
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn build_puzzle_image_prompt_keeps_puzzle_asset_constraints() {
+        let prompt = build_puzzle_image_prompt("雨夜神庙", "猫咪在发光遗迹前寻找线索");
+
+        assert!(prompt.contains("雨夜神庙"));
+        assert!(prompt.contains("猫咪在发光遗迹前寻找线索"));
+        assert!(prompt.contains("1:1 正方形拼图关卡"));
+        assert!(prompt.contains("3x3 或 4x4"));
+        assert!(prompt.contains("避免文字、水印、边框和 UI 元素"));
+    }
+
+    #[test]
+    fn build_puzzle_image_prompt_trims_long_user_description_for_wan22() {
+        let long_level_name = "雨夜神庙".repeat(20);
+        let long_description =
+            "发光遗迹、猫咪、漂浮碎片、雨水反光、远处灯塔、适合拼图切块。".repeat(50);
+        let prompt = build_puzzle_image_prompt(long_level_name.as_str(), long_description.as_str());
+
+        assert!(prompt.chars().count() <= PUZZLE_TEXT_TO_IMAGE_PROMPT_MAX_CHARS);
+        assert!(prompt.contains("1:1 正方形拼图关卡"));
+        assert!(prompt.contains("3x3 或 4x4"));
+        assert!(prompt.contains("避免文字、水印、边框和 UI 元素"));
+    }
+
+    #[test]
+    fn default_negative_prompt_blocks_text_and_low_quality_assets() {
+        assert!(PUZZLE_DEFAULT_NEGATIVE_PROMPT.contains("低清晰度"));
+        assert!(PUZZLE_DEFAULT_NEGATIVE_PROMPT.contains("文字水印"));
+    }
+}