"""Generate Sieve scripts from app rules and deploy to user's Dovecot.

Rule semantics → Sieve mapping:
  field: from/to/cc/subject/body/forwarded_from/forwarded_to/size
  op:    contains, not_contains, equals, starts, ends, matches, gt
  action: move, star, important, mark_read, delete, forward_copy, autoreply

Resulting script lives at /var/mail/sieve/<user>/managesieve.sieve inside DMS.
"""
from __future__ import annotations

import re
import subprocess
import os
from io import StringIO
from typing import Iterable

from .store import RuleDTO


_FIELD_TO_HEADER = {
    "from": "From", "to": "To", "cc": "Cc",
    "subject": "Subject",
    "forwarded_from": "X-Forwarded-From",
    "forwarded_to": "X-Forwarded-To",
}


def _q(s: str) -> str:
    return '"' + str(s).replace("\\", "\\\\").replace('"', '\\"') + '"'


def _condition(rule: RuleDTO) -> str | None:
    """Return Sieve test expression (without `if `) or None if unsupported."""
    f, op, v = rule.field, rule.op, rule.value
    if f == "body":
        match = {"contains": ":contains", "matches": ":matches"}.get(op, ":contains")
        return f'body :text {match} {_q(v)}'
    if f == "size":
        try:
            kb = int(v)
        except ValueError:
            kb = 0
        if op == "gt":
            return f"size :over {kb}K"
        return f"size :under {kb}K"
    header = _FIELD_TO_HEADER.get(f)
    if not header:
        return None
    if op == "equals":
        return f'header :is {_q(header)} {_q(v)}'
    if op == "starts":
        return f'header :matches {_q(header)} {_q(v + "*")}'
    if op == "ends":
        return f'header :matches {_q(header)} {_q("*" + v)}'
    if op == "matches":
        return f'header :matches {_q(header)} {_q(v)}'
    if op == "not_contains":
        return f'not header :contains {_q(header)} {_q(v)}'
    # default — contains
    return f'header :contains {_q(header)} {_q(v)}'


def _action(rule: RuleDTO) -> list[str]:
    a, p = rule.action, rule.action_param
    if a == "move":
        return [f"fileinto {_q(p or 'INBOX')};"]
    if a == "delete":
        return ["discard;", "stop;"]
    if a == "mark_read":
        return ["addflag \"\\\\Seen\";"]
    if a == "star":
        return ["addflag \"\\\\Flagged\";"]
    if a == "important":
        return ["addflag \"$Important\";"]
    if a == "forward_copy" and p:
        return [f"redirect :copy {_q(p)};"]
    if a == "autoreply" and p:
        return [
            'vacation :days 1 :subject "Re: ${subject}" '
            f'{_q(p)};'
        ]
    return []


def render(rules: Iterable[RuleDTO]) -> str:
    """Produce a complete sieve script for the given rules."""
    out = StringIO()
    out.write('require ["fileinto","imap4flags","copy","body","vacation","envelope"];\n\n')
    for r in rules:
        if not r.enabled:
            continue
        cond = _condition(r)
        if not cond:
            continue
        actions = _action(r)
        if not actions:
            continue
        out.write(f"# rule {r.id}: {r.name}\n")
        if not r.apply_to_spam:
            cond = f'allof(not header :contains "X-Spam-Flag" "YES", {cond})'
        out.write(f"if {cond} {{\n")
        for a in actions:
            out.write(f"    {a}\n")
        if not r.continue_chain:
            out.write("    stop;\n")
        out.write("}\n\n")
    return out.getvalue()


# ── Deploy to Dovecot ─────────────────────────────────────────────────────

def _container() -> str:
    return os.getenv("DMS_CONTAINER", "docker-mailserver-1")


def deploy(user_email: str, script: str) -> tuple[bool, str]:
    """Write the script to the user's Sieve dir inside the DMS container."""
    safe = re.sub(r"[^a-zA-Z0-9._@-]", "", user_email)
    if safe != user_email:
        return False, "invalid user_email"
    domain, local = "", user_email
    if "@" in user_email:
        local, domain = user_email.split("@", 1)
    target = f"/var/mail/{domain}/{local}/sieve/managesieve.sieve" if domain else f"/var/mail/{local}/sieve/managesieve.sieve"
    cmd = [
        "docker", "exec", "-i", _container(),
        "bash", "-c",
        f"mkdir -p $(dirname {target}) && cat > {target} && "
        f"chown -R 5000:5000 $(dirname {target}) && "
        f"sievec {target}",
    ]
    try:
        p = subprocess.run(cmd, input=script, text=True, capture_output=True, timeout=20)
    except Exception as exc:
        return False, str(exc)
    if p.returncode != 0:
        return False, (p.stderr or p.stdout).strip() or "error"
    return True, target