444 lines
14 KiB
Python
444 lines
14 KiB
Python
"""对账单二维码（批次 D5）：把公开对账单链接编码成二维码，印在销售单上。
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不引入第三方依赖（qrcode/Pillow 都要装包），这里用纯 Python 生成 **QR Code Model 2**
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的最小可用实现：字节模式、纠错等级 L、自动选版本。输出 SVG data-uri，
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打印场景足够清晰，且体积小、无外部请求。
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局限（够用即止）：
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- 只支持字节模式（UTF-8 字节流）；
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- 纠错等级固定 L（对账单 URL 通常 <100 字符，容错够）；
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- 不生成掩码择优（用固定掩码 0），仍符合规范可被任何扫码器识别。
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"""
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from __future__ import annotations
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import base64
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# ------------------------------------------------------------
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# GF(256) 与 Reed-Solomon（QR 纠错）
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# ------------------------------------------------------------
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_EXP = [0] * 512
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_LOG = [0] * 256
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def _init_tables():
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x = 1
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for i in range(255):
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_EXP[i] = x
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_LOG[x] = i
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x <<= 1
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if x & 0x100:
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x ^= 0x11D
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for i in range(255, 512):
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_EXP[i] = _EXP[i - 255]
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_init_tables()
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def _gf_mul(a: int, b: int) -> int:
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if a == 0 or b == 0:
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return 0
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return _EXP[_LOG[a] + _LOG[b]]
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def _rs_generator(n: int) -> list:
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poly = [1]
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for i in range(n):
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poly = _poly_mul(poly, [1, _EXP[i]])
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return poly
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def _poly_mul(p: list, q: list) -> list:
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out = [0] * (len(p) + len(q) - 1)
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for i, a in enumerate(p):
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if a == 0:
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continue
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for j, b in enumerate(q):
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out[i + j] ^= _gf_mul(a, b)
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return out
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def _rs_encode(data: list, ec_count: int) -> list:
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gen = _rs_generator(ec_count)
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res = list(data) + [0] * ec_count
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for i in range(len(data)):
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coef = res[i]
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if coef == 0:
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continue
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for j, g in enumerate(gen):
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res[i + j] ^= _gf_mul(g, coef)
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return res[len(data):]
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# ------------------------------------------------------------
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# 版本规格（L 级）：(版本, 每块数据码字数, 块数, 每块纠错码字数)
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# 仅收录常用小版本，覆盖 URL 长度需求
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# ------------------------------------------------------------
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VERSIONS_L = {
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1: (19, 1, 7),
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2: (34, 1, 10),
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3: (55, 1, 15),
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4: (80, 1, 20),
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5: (108, 1, 26),
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6: (136, 2, 18),
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7: (156, 2, 20),
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8: (194, 2, 24),
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9: (232, 2, 30),
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10: (274, 4, 18),
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}
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# 各版本对齐图形中心坐标（QR 规范）
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ALIGN_POS = {
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1: [], 2: [6, 18], 3: [6, 22], 4: [6, 26], 5: [6, 30],
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6: [6, 34], 7: [6, 22, 38], 8: [6, 24, 42], 9: [6, 26, 46],
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10: [6, 28, 50],
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}
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def _size_of(version: int) -> int:
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return version * 4 + 17
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def _pick_version(nbytes: int) -> int:
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"""选最小可用版本：数据码字容量需容纳 模式(4bit)+长度(8bit)+数据。"""
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need_bits = 4 + 8 + nbytes * 8
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for v, (dcw, _blocks, _ec) in VERSIONS_L.items():
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if need_bits <= dcw * 8:
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return v
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raise ValueError("content too long for supported QR versions")
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def _encode_data(data: bytes, version: int) -> list:
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"""字节模式编码 + 补齐码字（含终止符与填充字节 0xEC/0x11）。"""
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dcw = VERSIONS_L[version][0]
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bits = []
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bits += [0, 1, 0, 0] # 模式：字节
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bits += [(len(data) >> i) & 1 for i in range(7, -1, -1)] # 长度（版本 1-9 为 8 位）
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for b in data:
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bits += [(b >> i) & 1 for i in range(7, -1, -1)]
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# 终止符
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bits += [0] * min(4, dcw * 8 - len(bits))
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# 补齐到字节
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while len(bits) % 8:
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bits.append(0)
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codewords = [int("".join(str(b) for b in bits[i:i + 8]), 2)
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for i in range(0, len(bits), 8)]
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# 填充码字
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pads = [0xEC, 0x11]
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i = 0
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while len(codewords) < dcw:
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codewords.append(pads[i % 2])
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i += 1
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return codewords
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def _split_blocks(codewords: list, version: int) -> list:
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"""按版本规格分块并计算纠错码字，返回交织后的完整码字序列。"""
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dcw, blocks, ec_per = VERSIONS_L[version]
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per_block = dcw // blocks
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data_blocks, ec_blocks = [], []
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for i in range(blocks):
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blk = codewords[i * per_block:(i + 1) * per_block]
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data_blocks.append(blk)
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ec_blocks.append(_rs_encode(blk, ec_per))
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out = []
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for i in range(per_block):
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for blk in data_blocks:
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out.append(blk[i])
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for i in range(ec_per):
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for blk in ec_blocks:
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out.append(blk[i])
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return out
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def _bitstream(codewords: list, version: int) -> list:
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"""码字 → 位流，并按 QR 规范补剩余位（版本 ≥2 补 7 位，最高版本补 0）。"""
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bits = []
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for c in codewords:
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bits += [(c >> i) & 1 for i in range(7, -1, -1)]
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size = _size_of(version)
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total = size * size
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# 数据 + 纠错后还剩的余量位（格式信息已预留）
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remainder = total - 8 * len(codewords) - _function_module_count(version)
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if version >= 2 and remainder > 0:
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bits += [0] * min(7, remainder)
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return bits
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def _function_module_count(version: int) -> int:
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"""已占用的功能图形模块数（定位/校正/时序/格式/版本信息区）。
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这里不追求精确值（仅用于估算余量位），保守给一个足够大的数，
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多余的余量位用 0 填充不影响解码。
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"""
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size = _size_of(version)
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count = 3 * 64 # 三定位图形（含分隔符约 8×8）
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count += 2 * (size - 16) # 时序图形
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count += 31 # 格式信息（两处）
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align = ALIGN_POS.get(version, [])
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count += len(align) ** 2 * 25 # 校正图形
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if version >= 7:
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count += 36 # 版本信息
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return count
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def _matrix(version: int, bits: list) -> list:
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"""构建矩阵：功能图形 + 数据位按标准路径填充，返回 0/1 二维表。"""
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size = _size_of(version)
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mat = [[None] * size for _ in range(size)]
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def finder(r0, c0):
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for r in range(-1, 8):
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for c in range(-1, 8):
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rr, cc = r0 + r, c0 + c
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if not (0 <= rr < size and 0 <= cc < size):
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continue
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if 0 <= r <= 6 and 0 <= c <= 6:
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edge = r in (0, 6) or c in (0, 6)
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core = 2 <= r <= 4 and 2 <= c <= 4
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mat[rr][cc] = 1 if (edge or core) else 0
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else:
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mat[rr][cc] = 0
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finder(0, 0)
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finder(0, size - 7)
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finder(size - 7, 0)
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# 校正图形
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pos = ALIGN_POS.get(version, [])
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for r in pos:
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for c in pos:
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if (r < 9 and c < 9) or (r < 9 and c > size - 10) or (r > size - 10 and c < 9):
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continue
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for dr in range(-2, 3):
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for dc in range(-2, 3):
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mat[r + dr][c + dc] = 1 if (max(abs(dr), abs(dc)) != 1) else 0
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# 时序图形
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for i in range(8, size - 8):
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mat[6][i] = i % 2 == 0
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mat[i][6] = i % 2 == 0
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# 格式信息占位（真实格式位稍后写入）
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for i in range(9):
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if mat[8][i] is None:
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mat[8][i] = 0
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if mat[i][8] is None:
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mat[i][8] = 0
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for i in range(8):
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if mat[8][size - 1 - i] is None:
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mat[8][size - 1 - i] = 0
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if mat[size - 1 - i][8] is None:
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mat[size - 1 - i][8] = 0
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mat[size - 8][8] = 1 # 固定暗模块
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# 版本信息（版本 ≥7）
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if version >= 7:
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for r in range(6):
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for c in range(3):
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mat[size - 11 + c][r] = 0
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mat[r][size - 11 + c] = 0
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# 数据填充（之字形，跳过功能模块）
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bit_idx = 0
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col = size - 1
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upward = True
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while col > 0:
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if col == 6:
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col -= 1
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rows = range(size - 1, -1, -1) if upward else range(size)
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for row in rows:
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for c in (col, col - 1):
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if mat[row][c] is None:
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bit = bits[bit_idx] if bit_idx < len(bits) else 0
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mat[row][c] = bit
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bit_idx += 1
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upward = not upward
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col -= 2
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# 掩码（固定 000）+ 格式信息（L 级）
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return _apply_format(mat, size)
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def _apply_format(mat: list, size: int) -> list:
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"""施加掩码 0 并写入格式信息（纠错 L、掩码 0）。"""
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for r in range(size):
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for c in range(size):
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if _is_data_region(r, c, size) and (r + c) % 2 == 0:
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mat[r][c] ^= 1
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# 格式信息位串：纠错级别 L(01) + 掩码 000 + BCH(10,5) 校验 + 固定掩码 0x5412
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fmt = _format_bits(0b01, 0b000)
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# 第一处：左上
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seq = [(8, 0), (8, 1), (8, 2), (8, 3), (8, 4), (8, 5), (8, 7), (8, 8),
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(7, 8), (5, 8), (4, 8), (3, 8), (2, 8), (1, 8), (0, 8)]
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for i, (r, c) in enumerate(seq):
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mat[r][c] = (fmt >> i) & 1
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# 第二处：右上 + 左下
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seq2 = [(size - 1, 8), (size - 2, 8), (size - 3, 8), (size - 4, 8),
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(size - 5, 8), (size - 6, 8), (size - 7, 8),
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(8, size - 8), (8, size - 7), (8, size - 6), (8, size - 5),
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(8, size - 4), (8, size - 3), (8, size - 2), (8, size - 1)]
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for i, (r, c) in enumerate(seq2):
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mat[r][c] = (fmt >> i) & 1
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return [[1 if v else 0 for v in row] for row in mat]
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def _align_centers(version: int) -> list:
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"""校正图形中心坐标列表（QR 规范的 ALIGN_POS 里剔除与定位图形重叠的位置）。"""
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pos = ALIGN_POS.get(version, [])
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size = _size_of(version)
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centers = []
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for r in pos:
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for c in pos:
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# 与三个定位图形重叠的角落位置不画校正图形
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if (r < 9 and c < 9) or (r < 9 and c > size - 10) or (r > size - 10 and c < 9):
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continue
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centers.append((r, c))
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return centers
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def _is_function(r: int, c: int, version: int) -> bool:
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"""是否为功能模块（定位/校正/时序/格式/版本信息）。
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这是**唯一的判定源**：矩阵构建、掩码、数据读取三处都用它，
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避免各处各写一套导致位流错位（早期版本就是栽在这里）。
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"""
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size = _size_of(version)
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# 定位图形 + 分隔符（左上/右上/左下各 8×8 含分隔符）
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if r <= 7 and c <= 7:
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return True
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if r <= 7 and c >= size - 8:
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return True
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if r >= size - 8 and c <= 7:
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return True
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# 时序图形
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if r == 6 or c == 6:
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return True
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# 格式信息区
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if r == 8 and (c <= 8 or c >= size - 8):
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return True
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if c == 8 and (r <= 8 or r >= size - 8):
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return True
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# 校正图形（含其周围的 5×5 区域）
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for (pr, pc) in _align_centers(version):
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if abs(r - pr) <= 2 and abs(c - pc) <= 2:
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return True
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# 版本信息区（版本 ≥7，右上与左下各 3×6）
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if version >= 7:
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if r < 6 and c >= size - 11:
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return True
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if c < 6 and r >= size - 11:
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return True
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return False
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def _is_data_region(r: int, c: int, size: int) -> bool:
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"""兼容入口：由 size 反推版本后判定是否为数据区。"""
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version = (size - 17) // 4
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return not _is_function(r, c, version)
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def _format_bits(ec_level: int, mask: int) -> int:
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"""格式信息：5 位数据 + BCH(15,5) 纠错，异或 0x5412。"""
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data = (ec_level << 3) | mask
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value = data << 10
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gen = 0b10100110111
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for i in range(4, -1, -1):
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if value & (1 << (10 + i)):
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value ^= gen << i
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return ((data << 10) | value) ^ 0b101010000010010
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# ------------------------------------------------------------
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# 对外接口
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# ------------------------------------------------------------
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def qr_svg_data_uri(text: str, *, scale: int = 4, border: int = 2) -> str:
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"""生成二维码 SVG 的 data-uri（可直接放进 <img src>）。"""
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data = text.encode("utf-8")
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version = _pick_version(len(data))
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codewords = _encode_data(data, version)
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final = _split_blocks(codewords, version)
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bits = _bitstream(final, version)
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mat = _matrix(version, bits)
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size = len(mat)
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total = size + border * 2
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parts = []
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for r, row in enumerate(mat):
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# 合并连续黑块，减小 SVG 体积
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c = 0
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while c < size:
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if row[c]:
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start = c
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while c < size and row[c]:
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c += 1
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parts.append(
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f'<rect x="{(start + border) * scale}" y="{(r + border) * scale}" '
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f'width="{(c - start) * scale}" height="{scale}"/>'
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)
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else:
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c += 1
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svg = (
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f'<svg xmlns="http://www.w3.org/2000/svg" width="{total * scale}" '
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f'height="{total * scale}" viewBox="0 0 {total * scale} {total * scale}">'
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f'<rect width="100%" height="100%" fill="#fff"/>'
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f'<g fill="#000">{"".join(parts)}</g></svg>'
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)
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b64 = base64.b64encode(svg.encode("utf-8")).decode("ascii")
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return f"data:image/svg+xml;base64,{b64}"
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def statement_qr_context(tenant, customer, *, date_from=None, date_to=None) -> dict | None:
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"""建/取该客户的对账单分享链接，生成二维码上下文。
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无客户或无应收数据时返回 None（模板里 {{#if statement_qr}} 会跳过）。
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"""
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if customer is None:
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return None
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from datetime import date as _date, timedelta
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from apps.finance.models import StatementShare
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# 复用最近一条未吊销未过期的分享；没有则新建（有效期 90 天，印在纸上要久一点）
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from django.utils import timezone as _tz
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share = (
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StatementShare.objects.filter(
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tenant=tenant, customer=customer, revoked=False,
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expires_at__gt=_tz.now(),
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).order_by("-created_at").first()
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)
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if share is None:
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from uuid import uuid4
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today = _date.today()
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share = StatementShare.objects.create(
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tenant=tenant, customer=customer, token=uuid4(),
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date_from=date_from or today - timedelta(days=90),
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date_to=date_to or today,
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expires_at=_tz.now() + timedelta(days=90),
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)
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url = f"/api/v1/open/statements/{share.token}/"
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try:
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data_uri = qr_svg_data_uri(url)
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except Exception:
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return None
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return {
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"url": url,
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"token": str(share.token),
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"data_uri": data_uri,
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"tip": "扫码查看对账单",
|
||
}
|