#!/usr/bin/env python3
"""daybook-ensure — the day's work-log note exists before anyone remembers to want it.

Two previous attempts at this log died inside four weeks (`daily-log/` 4 entries, `sessions/`
3, both Mar-Apr 2026). Neither had a trigger; both depended on someone remembering. This hook
removes the remembering: at every session start the day's note exists, skeleton in place, so
writing into it is an append rather than a decision to begin.

Deliberately narrow:
  - CREATES only. An existing note is never opened for writing, never rewritten, never
    reordered. The prose is the executor's and the hook must not be able to damage it.
  - Says so when it fails. The job this replaces died silently for five months behind a
    `> /dev/null 2>&1` (see the 2026-08-23 daily note). A hook that cannot write must
    announce that, not shrug. Constitutional Constraint #4, at hook scale.
  - Always exits 0. Honest reporting must never cost the steward a session.
"""
import datetime, os, sys

VAULT = os.path.expanduser(
    "~/Library/Mobile Documents/iCloud~md~obsidian/Documents/David, root-and-branch")
DAILY = os.path.join(VAULT, "01. Daily")

SKELETON = """---
title: "{date} — {dayname}"
type: daily
date: {date}
status: active
tags:
  - daily
  - worklog
---

# {date} — {dayname}

*A plain-language record of the day's work, so the history is readable without reading `git log`.
Project work sits under its own heading; decisions, insights and open threads are collected at the end.*

## The day in short

## Decisions taken

## Insights and exchanges worth keeping

## Open / next
"""


def note_path(day, daily_dir=DAILY):
    return os.path.join(daily_dir, f"{day.isoformat()}.md")


def ensure(day=None, daily_dir=DAILY):
    """-> (status, path). status in {'exists','created','no-dir','error:<msg>'}.

    'exists' is not a failure and 'created' is not a success worth announcing loudly —
    the caller decides what is worth a line of the steward's attention.
    """
    day = day or datetime.date.today()
    p = note_path(day, daily_dir)
    try:
        if not os.path.isdir(daily_dir):
            return "no-dir", p
        if os.path.exists(p):
            return "exists", p
        body = SKELETON.format(date=day.isoformat(), dayname=day.strftime("%A"))
        # x-mode: refuse to clobber if something raced us between the check and the write.
        with open(p, "x", encoding="utf-8") as fh:
            fh.write(body)
        return "created", p
    except FileExistsError:
        return "exists", p
    except OSError as e:
        return f"error:{e.__class__.__name__}", p


def selftest():
    import tempfile, shutil
    ok = fail = 0

    def chk(label, cond):
        nonlocal ok, fail
        print(f"  [{'ok  ' if cond else 'FAIL'}] {label}")
        ok, fail = (ok + (1 if cond else 0), fail + (0 if cond else 1))

    d = tempfile.mkdtemp()
    try:
        day = datetime.date(2026, 8, 23)
        st, p = ensure(day, d)
        chk("creates the note when absent", st == "created" and os.path.exists(p))
        txt = open(p, encoding="utf-8").read()
        chk("skeleton carries the ISO date and weekday", "2026-08-23" in txt and "Sunday" in txt)
        chk("skeleton is spec-conformant (type/status/tags present)",
            "type: daily" in txt and "status: active" in txt and "worklog" in txt)

        # THE control that matters: an existing note must survive untouched.
        open(p, "w", encoding="utf-8").write("PROSE THE EXECUTOR WROTE\n")
        st2, _ = ensure(day, d)
        chk("does NOT overwrite an existing note  [the whole point]",
            st2 == "exists" and open(p, encoding="utf-8").read() == "PROSE THE EXECUTOR WROTE\n")
        chk("reports 'exists' rather than 'created' on the second run", st2 == "exists")

        missing = os.path.join(d, "nope")
        st3, _ = ensure(day, missing)
        chk("reports a missing directory instead of creating one  [no silent mkdir]",
            st3 == "no-dir" and not os.path.exists(missing))

        # positive control: the failure path must be reachable, or 'no-dir' proves nothing.
        st4, _ = ensure(day, d)
        chk("the same call succeeds where the directory exists  [positive control — proves"
            " 'no-dir' reports the directory, not a broken function]", st4 == "exists")
    finally:
        shutil.rmtree(d, ignore_errors=True)

    print(f"\n{'SELFTEST PASS' if not fail else 'SELFTEST FAIL'} — {ok} ok, {fail} failed")
    return 0 if not fail else 1


if __name__ == "__main__":
    if "--selftest" in sys.argv:
        sys.exit(selftest())
    status, path = ensure()
    if status == "created":
        print(f"DAYBOOK — created {os.path.basename(path)}")
    elif status.startswith("error") or status == "no-dir":
        # Loud on purpose. The predecessor's silence cost five months.
        print(f"DAYBOOK — COULD NOT WRITE the day's note ({status}). "
              f"Expected at: {path}")
    sys.exit(0)