#!/usr/bin/env python3
"""echo_session.py — the session-end bundle: one call ends a session correctly. [2.1.0]

Ending a substantive session used to take four-plus separate invocations (session-log
PUT, Agent Log append, heartbeat PUT, optional scope set, optional reflect apply) —
a cost per session, and a partial failure left broken orientation state (log written
but heartbeat stale). This verb does all of it in one call, under ONE advisory-lock
acquisition, in a fixed order with the heartbeat written LAST as the commit marker:
a failure part-way leaves the previous pointer intact, never a dangling one.

Bundle shape (JSON object):
  {
    "slug":           "echo-mcp-spec",          # required, kebab-case
    "log_body":       "<full session-log markdown, frontmatter included>",  # required
    "agent_log_line": "- 2026-07-28: ...",      # optional; derived when omitted
    "scope":          "new scope text",          # optional -> scope set
    "reflect":        [ { ...PROPOSAL_SCHEMA... } ]   # optional -> routed via capture
  }

Dry-run by default (previews the whole plan, reflect included); --apply writes.
Times: the filename HHMM comes from $ECHO_NOW (HHMM) else the local clock; the date
from ECHO_TODAY via echo.today(). Offline: every step rides the offline queue, so a
session end during an outage queues durably instead of failing.

CLI: echo.py session-end <bundle.json> [--apply]
"""
from __future__ import annotations

import datetime as dt
import json
import os
import re
import sys
from pathlib import Path

sys.path.insert(0, str(Path(__file__).resolve().parent))
import echo  # noqa: E402

SESSION_RE = re.compile(r"^\d{4}-\d{2}-\d{2}-\d{4}-[a-z0-9-]+\.md$")
SLUG_RE = re.compile(r"^[a-z0-9][a-z0-9-]*$")


def _hhmm() -> str:
    v = os.environ.get("ECHO_NOW", "").strip()
    if v:
        if not re.match(r"^\d{4}$", v):
            raise echo.EchoError(f"session-end: $ECHO_NOW must be HHMM, got '{v}'", 2)
        return v
    return dt.datetime.now().strftime("%H%M")


def validate(bundle: dict) -> tuple[str, str]:
    """Return (session_path, agent_log_line) or raise EchoError(2). Validation runs
    BEFORE any write — a bad bundle writes nothing at all."""
    if not isinstance(bundle, dict):
        raise echo.EchoError("session-end: bundle must be a JSON object", 2)
    slug = str(bundle.get("slug", "")).strip()
    if not SLUG_RE.match(slug):
        raise echo.EchoError(f"session-end: slug must be kebab-case, got '{slug}'", 2)
    if not str(bundle.get("log_body", "")).strip():
        raise echo.EchoError("session-end: log_body is required (the full session-log markdown)", 2)
    reflect = bundle.get("reflect")
    if reflect is not None and not isinstance(reflect, list):
        raise echo.EchoError("session-end: reflect must be a JSON array of proposals", 2)
    fname = f"{echo.today()}-{_hhmm()}-{slug}.md"
    if not SESSION_RE.match(fname):
        raise echo.EchoError(f"session-end: derived filename '{fname}' violates the "
                             "canonical YYYY-MM-DD-HHMM-<slug>.md form", 2)
    path = f"_agent/sessions/{fname}"
    line = str(bundle.get("agent_log_line") or "").strip() \
        or f"- {echo.today()}: session logged [[{path[:-3]}]]"
    return path, line


def session_end(bundle: dict, apply: bool = False) -> int:
    import echo_reflect
    path, line = validate(bundle)
    scope = str(bundle.get("scope") or "").strip()
    proposals = bundle.get("reflect") or []

    valid, errors = echo_reflect.validate(proposals)
    for e in errors:
        print(f"skip: {e}", file=sys.stderr)

    print(f"session-end plan ({'APPLY' if apply else 'dry-run'}):")
    print(f"  1. session log -> {path}")
    print(f"  2. agent-log line: {line}")
    if valid:
        echo_reflect.classify(valid)
        print(f"  3. reflect: {len(valid)} proposal(s)")
        print(echo_reflect.preview(valid))
    else:
        print("  3. reflect: (none)")
    print(f"  4. scope set: {scope!r}" if scope else "  4. scope: (unchanged)")
    print(f"  5. heartbeat -> {path} @ <now>   (written LAST — the commit marker)")

    if not apply:
        print("\nsession-end: dry-run — re-run with --apply to write.")
        return 0

    import echo_concurrency
    import echo_ops
    steps: dict[str, str] = {}
    with echo_concurrency.vault_lock():
        # 1. The session log itself. A hard failure here aborts the whole bundle —
        #    nothing after it (including the heartbeat) runs, so orientation state
        #    can never point at a log that was never written.
        echo.cmd_put(path, echo.temp_file(str(bundle["log_body"]).encode("utf-8")))
        steps["session_log"] = "ok"
        # 2. Agent-log line (best-effort by contract; queues itself when offline).
        echo_ops.ensure_daily_log(line)
        steps["agent_log"] = "ok"
        # 3. Reflect proposals through the normal capture path (gate-aware).
        if valid:
            gated = 0
            for p in valid:
                if p.get("_action") == "error":
                    continue
                bodyfile = echo.temp_file((p.get("body") or "").encode()) if p.get("body") else None
                rc = echo_ops.capture(
                    p.get("kind"), p["title"], bodyfile,
                    aliases=p.get("aliases") or [], sources=p.get("sources") or [],
                    tags=p.get("tags") or [], date=p.get("date"),
                    domain=p.get("domain", "business"),
                    inbox=bool(p.get("inbox")) or not p.get("kind"))
                gated += 1 if rc == 76 else 0
            steps["reflect"] = f"{len(valid) - gated}/{len(valid)} applied" \
                + (f", {gated} gated (re-propose with --merge-into)" if gated else "")
        else:
            steps["reflect"] = "skipped (none)"
        # 4. Scope switch (optional).
        if scope:
            echo.cmd_scope("set", scope)
            steps["scope"] = "ok"
        else:
            steps["scope"] = "unchanged"
        # 5. Heartbeat LAST — the commit marker for the whole bundle.
        echo.cmd_put("_agent/heartbeat/last-session.md",
                     echo.temp_file(f"{path} @ {echo.now_iso()}\n".encode("utf-8")))
        steps["heartbeat"] = "ok"

    print("\nsession-end: done — "
          + "; ".join(f"{k}: {v}" for k, v in steps.items()))
    return 0