"""Daily Brief HTML rendering.

Pure-stdlib module — has no dependencies on the rest of the app, so it can
be imported by preview scripts, tests, and the scheduler alike. The shape
of the items list matches a SELECT * from the `daily_brief` table.
"""
from __future__ import annotations

import json


def build_brief_html(items: list[dict]) -> str:
    """Render the Daily Brief email body from `daily_brief` rows.

    Sections rendered (in order, only if non-empty):
        1. Ambiguous Routings — `reason == "ambiguous"`
        2. MTRs Missing Heat Code — `reason == "mtr_no_heat_code"`
        3. Processing Errors — `reason == "error"`

    If all sections are empty, returns a short "nothing to report" body.
    """
    ambiguous = [i for i in items if i["reason"] == "ambiguous"]
    no_heat   = [i for i in items if i["reason"] == "mtr_no_heat_code"]
    unmatched = [i for i in items if i["reason"] == "client_unmatched"]
    errors    = [i for i in items if i["reason"] == "error"]

    sections: list[str] = []

    # One-line summary at top so ops doesn't need to count rows.
    summary_bits = []
    if ambiguous: summary_bits.append(f"{len(ambiguous)} ambiguous routing(s)")
    if no_heat:   summary_bits.append(f"{len(no_heat)} MTR(s) without a heat code")
    if unmatched: summary_bits.append(f"{len(unmatched)} unmatched sender domain(s)")
    if errors:    summary_bits.append(f"{len(errors)} processing error(s)")
    if summary_bits:
        sections.append(
            f"<p>Today's automation summary: {'; '.join(summary_bits)}.</p>"
        )

    if ambiguous:
        rows = ""
        for item in ambiguous:
            scores: dict = (
                json.loads(item["confidence_scores"])
                if item.get("confidence_scores") else {}
            )
            score_cols = "".join(
                f"<td>{doc_type}: {score:.2%}</td>"
                for doc_type, score in sorted(scores.items())
            )
            rows += (
                f"<tr>"
                f"<td>{item.get('sender_email', '')}</td>"
                f"<td>{item.get('subject', '')}</td>"
                f"<td>{item.get('attachment_filename', '')}</td>"
                f"{score_cols}"
                f"</tr>"
            )
        first_scores = (
            json.loads(ambiguous[0]["confidence_scores"])
            if ambiguous[0].get("confidence_scores") else {}
        )
        score_headers = "".join(
            f"<th>{doc_type}</th>" for doc_type in sorted(first_scores.keys())
        )
        sections.append(
            "<h2>Ambiguous Routings</h2>"
            "<p>These attachments scored above the confidence threshold for "
            "more than one document type and were not auto-routed. Review and "
            "file manually.</p>"
            "<table border='1' cellpadding='4' cellspacing='0'>"
            f"<tr><th>Sender</th><th>Subject</th><th>Attachment</th>{score_headers}</tr>"
            f"{rows}"
            "</table>"
        )

    if no_heat:
        rows = ""
        for item in no_heat:
            rows += (
                f"<tr>"
                f"<td>{item.get('sender_email', '')}</td>"
                f"<td>{item.get('subject', '')}</td>"
                f"<td>{item.get('attachment_filename', '')}</td>"
                f"</tr>"
            )
        sections.append(
            "<h2>MTRs Missing Heat Code</h2>"
            "<p>These MTRs were uploaded to <code>MTR/_no_heat_code/</code> "
            "because no heat code could be extracted from the document. "
            "Please review the file in Dropbox, identify the heat code(s), "
            "and move/copy under the correct <code>MTR/&lt;heat_code&gt;/</code> "
            "folder.</p>"
            "<table border='1' cellpadding='4' cellspacing='0'>"
            "<tr><th>Sender</th><th>Subject</th><th>Attachment</th></tr>"
            f"{rows}"
            "</table>"
        )

    if unmatched:
        rows = ""
        for item in unmatched:
            rows += (
                f"<tr>"
                f"<td>{item.get('sender_email', '')}</td>"
                f"<td>{item.get('subject', '')}</td>"
                f"<td>{item.get('attachment_filename', '')}</td>"
                f"</tr>"
            )
        sections.append(
            "<h2>Unmatched Sender Domains</h2>"
            "<p>These POs/Invoices were uploaded to "
            "<code>POs/_unmatched/</code> or <code>Invoices/_unmatched/</code> "
            "because the sender's email domain isn't in the client mapping. "
            "Move the file under the right client folder in Dropbox, then "
            "add the domain → client mapping to "
            "<code>scripts/seed_client_domains.json</code> and re-run the "
            "seeder so future emails route correctly.</p>"
            "<table border='1' cellpadding='4' cellspacing='0'>"
            "<tr><th>Sender</th><th>Subject</th><th>Attachment</th></tr>"
            f"{rows}"
            "</table>"
        )

    if errors:
        rows = ""
        for item in errors:
            rows += (
                f"<tr>"
                f"<td>{item.get('sender_email', '')}</td>"
                f"<td>{item.get('subject', '')}</td>"
                f"<td>{item.get('attachment_filename', '')}</td>"
                f"<td>{item.get('error_message', '')}</td>"
                f"</tr>"
            )
        sections.append(
            "<h2>Processing Errors</h2>"
            "<p>These attachments raised an exception during processing. "
            "Stack traces are in the processor log files.</p>"
            "<table border='1' cellpadding='4' cellspacing='0'>"
            "<tr><th>Sender</th><th>Subject</th><th>Attachment</th><th>Error</th></tr>"
            f"{rows}"
            "</table>"
        )

    if not sections:
        return (
            "<html><body>"
            "<p>No items to report today — all attachments routed cleanly.</p>"
            "</body></html>"
        )

    return f"<html><body>{''.join(sections)}</body></html>"