"""Email templates for job notifications."""

from __future__ import annotations

from datetime import datetime, UTC
from typing import Iterable, Mapping, Dict, Any

DEFAULT_DATETIME_FORMAT = "%Y-%m-%d %H:%M"
DEFAULT_JOB_ALERT_SUBJECT = "{count_label}{scope}"
DEFAULT_JOB_ALERT_BODY = (
    "Hi,\n\n{intro_line}{jobs_section}\n\nGenerated at {timestamp} UTC.\n"
    "You are receiving this message because job alerts are enabled.\n"
)


class _SafeDict(dict):
    def __missing__(self, key: str) -> str:
        return ""


def _format_template(template: str, context: Dict[str, Any]) -> str:
    safe_context = _SafeDict(
        {k: ("\n".join(str(v) for v in context[k]) if isinstance(
            context[k], list) else context[k]) for k in context}
    )
    return template.format_map(safe_context)


def render_job_alert_email(
    jobs: Iterable[Mapping[str, object]],
    *,
    region: str | None = None,
    keyword: str | None = None,
    generated_at: datetime | None = None,
    template_override: Mapping[str, str] | None = None,
) -> dict[str, Any]:
    """Render the subject/body for a job alert email.

    Returns a dict with subject/body strings and the context used to render them.
    """

    job_list = list(jobs)
    generated_at = generated_at or datetime.now(UTC)
    timestamp = generated_at.strftime(DEFAULT_DATETIME_FORMAT)

    scope_parts = []
    if region:
        scope_parts.append(f"region: {region}")
    if keyword:
        scope_parts.append(f"keyword: {keyword}")
    scope = " (" + ", ".join(scope_parts) + ")" if scope_parts else ""

    job_lines: list[str] = []
    for index, job in enumerate(job_list, start=1):
        title = str(job.get("title", "Untitled"))
        company = str(job.get("company", "Unknown company"))
        location = str(job.get("location", "N/A"))
        url = str(job.get("url", ""))
        line = f"{index}. {title} — {company} ({location})"
        job_lines.append(line)
        if url:
            job_lines.append(f"   {url}")

    if job_lines:
        jobs_section = "\n" + "\n".join(job_lines)
    else:
        jobs_section = "\nNo jobs matched this alert."
    jobs_message = jobs_section.strip()
    context: Dict[str, Any] = {
        "count": len(job_list),
        "count_label": "No new jobs" if not job_list else f"{len(job_list)} new jobs",
        "scope": scope,
        "region": region or "",
        "keyword": keyword or "",
        "timestamp": timestamp,
        "generated_at": generated_at,
        "intro_line": "Here are the latest jobs discovered by the scraper:",
        "jobs_message": jobs_message,
        "jobs_section": jobs_section,
        "jobs_lines": job_lines,
        "has_jobs": bool(job_list),
    }

    template = template_override
    if template is None:
        try:
            from web.db import get_email_template_by_slug

            template = get_email_template_by_slug("job-alert")
        except Exception:
            template = None

    template_subject = (template or {}).get(
        "subject") or DEFAULT_JOB_ALERT_SUBJECT
    template_body = (template or {}).get("body") or DEFAULT_JOB_ALERT_BODY

    subject = _format_template(template_subject, context)
    body = _format_template(template_body, context)

    result = {
        "subject": subject,
        "body": body,
        "context": context,
        "template_slug": (template or {}).get("slug", "job-alert"),
    }
    return result