from __future__ import annotations

import json

from app.services.normalize import RawRead

from app.services.parsers.base import BaseParser, ParseResult

class JsonFlockParser(BaseParser):

    """Handles a top-level list of read objects, or a wrapper like

    {"reads": [...]} / {"data": [...]} / {"results": [...]}. Nested objects are flattened

    one level (e.g. read["camera"]["id"] -> "camera_id") so the alias mapper can find them."""

    name = "json_flock"

    _WRAPPERS = ("reads", "data", "results", "records", "plate_reads", "items")

    def parse(self, data: bytes) -> ParseResult:

        errors: list[str] = []

        try:

            doc = json.loads(data.decode("utf-8-sig", errors="replace"))

        except json.JSONDecodeError as e:

            return ParseResult(headers=[], rows=[], errors=[f"invalid json: {e}"])

        records = doc

        if isinstance(doc, dict):

            for w in self._WRAPPERS:

                if isinstance(doc.get(w), list):

                    records = doc[w]

                    break

            else:

                records = [doc]

        if not isinstance(records, list):

            return ParseResult(headers=[], rows=[], errors=["json root is not a list of reads"])

        rows: list[RawRead] = []

        header_set: dict[str, None] = {}

        for i, rec in enumerate(records, start=1):

            if not isinstance(rec, dict):

                errors.append(f"row {i}: not an object")

                continue

            flat = self._flatten(rec)

            for k in flat:

                header_set.setdefault(k, None)

            rows.append(RawRead(fields=flat, source_row=i))

        return ParseResult(headers=list(header_set), rows=rows, errors=errors)

    @staticmethod

    def _flatten(rec: dict) -> dict:

        out: dict = {}

        for k, v in rec.items():

            if isinstance(v, dict):

                for k2, v2 in v.items():

                    out[f"{k}_{k2}"] = v2

            elif isinstance(v, list):

                out[k] = json.dumps(v)

            else:

                out[k] = v

        return out