#!/usr/bin/env python3
"""yaml_patch.py — 对 sources/*.yaml 做**行级**字段回填，保留注释与原有格式。

为什么需要它：
`yaml.safe_load` + `yaml.safe_dump` 会把整个文件重写，**注释全部丢失**。
sources/*.yaml 里的注释承载了关键信息（下载模板、许可解释、未纳入原因、运维提示），
必须保住。因此所有自动回填（fetch_source.py / oss_sync.py）统一走本模块的行级替换。

约定的缩进层级（与 sources/*.yaml 一致）：
    sources:
      - id: <source_id>        # 2 空格 + "- "
        status: planned        # 4 空格
        items:
          - id: <item_id>      # 6 空格 + "- "
            oss_key: ...       # 8 空格
"""
import re


def _yaml_scalar(v):
    """把 Python 值渲染成 YAML 标量。"""
    if v is None:
        return "null"
    if isinstance(v, bool):
        return "true" if v else "false"
    if isinstance(v, (int, float)):
        return str(v)
    s = str(v)
    # 需要引号的情况：空串、含特殊起始字符、含冒号空格、纯数字样式
    if s == "" or s[0] in "&*?|-<>=!%@`{[\"'" or ": " in s or s.endswith(":"):
        return '"' + s.replace('\\', '\\\\').replace('"', '\\"') + '"'
    return s


def patch_item_fields(path, source_id, item_id, fields):
    """回填某 source 下某 item 的字段。返回 True 表示有改动。

    fields: dict，如 {"sha256": "ab..", "size": 123, "status": "fetched"}
    已存在的键 → 原地替换；不存在的键 → 追加到该 item 块末尾。
    """
    with open(path, encoding="utf-8") as f:
        lines = f.read().split("\n")

    src_re = re.compile(r"^  - id: (\S+)\s*$")
    item_re = re.compile(r"^      - id: (\S+)\s*$")

    # 1) 定位 source 块范围
    s_start = s_end = None
    for i, ln in enumerate(lines):
        m = src_re.match(ln)
        if m:
            if m.group(1) == source_id and s_start is None:
                s_start = i
            elif s_start is not None and s_end is None:
                s_end = i
                break
    if s_start is None:
        return False
    if s_end is None:
        s_end = len(lines)

    # 2) 在 source 块内定位 item 块范围
    i_start = i_end = None
    for i in range(s_start, s_end):
        m = item_re.match(lines[i])
        if m:
            if m.group(1) == item_id and i_start is None:
                i_start = i
            elif i_start is not None and i_end is None:
                i_end = i
                break
    if i_start is None:
        return False
    if i_end is None:
        # item 块延伸到 source 块末尾；剔除尾部空行与注释行
        j = s_end - 1
        while j > i_start and (lines[j].strip() == "" or lines[j].lstrip().startswith("#")):
            j -= 1
        i_end = j + 1

    # 3) 逐字段替换或追加
    changed = False
    for key, val in fields.items():
        new_line = f"        {key}: {_yaml_scalar(val)}"
        hit = None
        for i in range(i_start, i_end):
            if re.match(rf"^        {re.escape(key)}:", lines[i]):
                hit = i
                break
        if hit is not None:
            if lines[hit] != new_line:
                lines[hit] = new_line
                changed = True
        else:
            lines.insert(i_end, new_line)
            i_end += 1
            changed = True

    if changed:
        with open(path, "w", encoding="utf-8") as f:
            f.write("\n".join(lines))
    return changed


def patch_source_fields(path, source_id, fields):
    """回填 source 级字段（如 status / fetched_at）。返回 True 表示有改动。"""
    with open(path, encoding="utf-8") as f:
        lines = f.read().split("\n")

    src_re = re.compile(r"^  - id: (\S+)\s*$")
    s_start = s_end = None
    for i, ln in enumerate(lines):
        m = src_re.match(ln)
        if m:
            if m.group(1) == source_id and s_start is None:
                s_start = i
            elif s_start is not None and s_end is None:
                s_end = i
                break
    if s_start is None:
        return False
    if s_end is None:
        s_end = len(lines)

    # items: 之前才是 source 级字段区
    limit = s_end
    for i in range(s_start, s_end):
        if re.match(r"^    items:", lines[i]):
            limit = i
            break

    changed = False
    for key, val in fields.items():
        new_line = f"    {key}: {_yaml_scalar(val)}"
        hit = None
        for i in range(s_start, limit):
            if re.match(rf"^    {re.escape(key)}:", lines[i]):
                hit = i
                break
        if hit is not None:
            if lines[hit] != new_line:
                lines[hit] = new_line
                changed = True
        else:
            lines.insert(limit, new_line)
            limit += 1
            changed = True

    if changed:
        with open(path, "w", encoding="utf-8") as f:
            f.write("\n".join(lines))
    return changed