"""Stage-2 of the OCR pipeline: parse raw OCR text into structured invoice
fields via the configured LLM provider.

Mirrors the pattern in fusion_accounting_followup/services/followup_text_generator.py:
look up an adapter by ir.config_parameter, fall back gracefully when no
provider is configured, and never let an LLM hiccup nuke the OCR result.
"""

import json
import logging

_logger = logging.getLogger(__name__)


SYSTEM_PROMPT = (
    "You are an invoice field extraction assistant. You read raw OCR text "
    "from vendor bills and return a strict JSON object with the requested "
    "fields. You never include commentary or markdown fences. When a field "
    "cannot be determined from the text you return null for that field."
)

USER_PROMPT = """Given the raw OCR text of a vendor bill, return a JSON object
with these fields (use null when unclear):

{{
  "vendor_name": <string, the seller/vendor company name>,
  "invoice_number": <string, the bill or invoice reference number>,
  "invoice_date": <string, ISO format YYYY-MM-DD>,
  "due_date": <string or null, ISO format YYYY-MM-DD>,
  "currency": <string, ISO 4217 code like CAD/USD/EUR>,
  "subtotal": <number or null>,
  "tax_total": <number or null>,
  "total": <number, the grand total amount due>,
  "line_items": [
    {{"description": <string>, "quantity": <number or null>,
      "unit_price": <number or null>, "amount": <number or null>}}
  ]
}}

Return ONLY valid JSON, no commentary, no markdown fences.

Raw OCR text:
---
{text}
---
"""


def parse_invoice_fields(env, raw_text: str, *, provider=None) -> dict:
    """Use the configured LLM provider to extract structured invoice fields.

    Returns a dict with the schema above. On any failure (no provider, bad
    JSON, network error, etc.) returns an all-null result so the OCR raw
    text is still preserved for the AP user.
    """
    if not raw_text or not raw_text.strip():
        return _empty_result()

    if provider is None:
        provider = _get_provider(env)
    if provider is None:
        _logger.info(
            "No LLM provider configured for OCR field parsing; "
            "raw OCR text preserved, fields left empty."
        )
        return _empty_result()

    try:
        truncated = raw_text[:12000]
        user = USER_PROMPT.format(text=truncated)
        response = provider.complete(
            system=SYSTEM_PROMPT,
            messages=[{'role': 'user', 'content': user}],
            max_tokens=1000,
            temperature=0.1,
        )
        content = response.get('content') if isinstance(response, dict) else response
        if not content:
            return _empty_result()

        # LLMs sometimes wrap JSON in ```json ... ``` despite instructions.
        content = content.strip()
        if content.startswith('```'):
            content = content.split('```', 2)[1]
            if content.startswith('json'):
                content = content[4:]
            content = content.rsplit('```', 1)[0]

        parsed = json.loads(content.strip())
        return {
            'vendor_name': parsed.get('vendor_name'),
            'invoice_number': parsed.get('invoice_number'),
            'invoice_date': parsed.get('invoice_date'),
            'due_date': parsed.get('due_date'),
            'currency': parsed.get('currency'),
            'subtotal': parsed.get('subtotal'),
            'tax_total': parsed.get('tax_total'),
            'total': parsed.get('total'),
            'line_items': parsed.get('line_items') or [],
        }
    except json.JSONDecodeError as e:
        _logger.warning("LLM returned non-JSON for OCR field parsing: %s", e)
        return _empty_result()
    except Exception as e:
        _logger.warning("OCR field parsing failed: %s", e)
        return _empty_result()


def _empty_result():
    return {
        'vendor_name': None,
        'invoice_number': None,
        'invoice_date': None,
        'due_date': None,
        'currency': None,
        'subtotal': None,
        'tax_total': None,
        'total': None,
        'line_items': [],
    }


def _get_provider(env):
    """Look up the LLM adapter via ir.config_parameter.

    Honours a feature-specific override
    (``fusion_accounting.provider.ocr_field_parsing``) before falling back
    to the suite-wide default (``fusion_accounting.provider.default``).
    Returns None when no adapter is configured/importable.
    """
    param = env['ir.config_parameter'].sudo()
    name = param.get_param('fusion_accounting.provider.ocr_field_parsing')
    if not name:
        name = param.get_param('fusion_accounting.provider.default')
    if not name:
        return None
    try:
        from odoo.addons.fusion_accounting_ai.services.adapters.openai_adapter import OpenAIAdapter
        from odoo.addons.fusion_accounting_ai.services.adapters.claude import ClaudeAdapter
    except ImportError:
        return None
    try:
        if name.startswith('openai'):
            return OpenAIAdapter(env)
        if name.startswith('claude'):
            return ClaudeAdapter(env)
    except Exception as e:
        _logger.warning("OCR field parser could not instantiate %s: %s", name, e)
        return None
    return None