"""`wikitool review` core (Gitea #125; design in #119 D3/D8/D10/D26).

The weekly review joins the task tracker (`chemenu.tasks`, #124) against the
`kb/gtd/` project pages over the case-normalized project name
(`chemenu.tasks.protocol.normalize_project_name`, #119 D8) - a join done at
*read time* and never stored (#119 D3, the `reports/` posture: never
re-derive, always compile, but nothing here is a compiled artifact). This
module owns the five checks and their data flow; `chemenu.commands.review_cmd`
owns the CLI adapter, flags and rendering.

Every provider read is wrapped individually so a single unreachable call
degrades the affected checks rather than the whole report: `projects()`
failing skips checks 1/2/3/4 (they all need the project list), `someday_items()`
failing skips only check 5, and a single project's `open_items()` failing
skips that one project everywhere without aborting the others. A `ReviewReport`
with anything in `checks_skipped` is, by construction, never mistaken for a
quiet week - see `ReviewReport.complete` and `commands.review_cmd`'s exit code.
"""
from __future__ import annotations

from dataclasses import dataclass
from datetime import date
from pathlib import Path
from typing import Optional

from chemenu import config, kb_scan
from chemenu.errors import ValidationError
from chemenu.tasks import build_reader
from chemenu.tasks import config as tasks_config
from chemenu.tasks.protocol import OpenItems, ReadSource, normalize_project_name

CHECK_STALLED = "stalled"
CHECK_WAITING_OVERDUE = "waiting_overdue"
CHECK_UNPAGED_PROJECT = "unpaged_project"
CHECK_NO_OPEN_LOOP = "no_open_loop"
CHECK_SOMEDAY_STALE = "someday_stale"

# D3 (Gitea #139): a value a provider could not supply is reported as its own
# finding, under checks 2 and 3 respectively, rather than silently skipped -
# a real state both `superproductivity` (a task with neither `dueWithTime`
# nor `dueDay`) and `caldav` (no server in the account returns
# `DAV:creationdate`, so `created` falls back to the earliest item's own
# `CREATED`, `None` for an empty project) can produce. Not separate entries
# in `ALL_CHECKS`: each fires from within check 2's/check 3's own loop, so
# the five-checks-run count is unaffected.
CHECK_WAITING_NO_FOLLOWUP = "waiting_no_follow_up"
CHECK_PROJECT_AGE_UNKNOWN = "project_age_unknown"

# The checks that need the full tracker project list (#119 D26 checks 1/2/3/4)
# - `projects()` failing skips all four together, since none of them can be
# answered from `someday_items()` alone.
_PROJECT_LIST_CHECKS = (CHECK_STALLED, CHECK_WAITING_OVERDUE, CHECK_UNPAGED_PROJECT, CHECK_NO_OPEN_LOOP)

ALL_CHECKS = (*_PROJECT_LIST_CHECKS, CHECK_SOMEDAY_STALE)


@dataclass(frozen=True)
class Finding:
    """One reported mismatch. `project` is the display name - the kb/ page's
    title when a check is anchored on the kb/ side (checks 1 and 4, where the
    kb/ page is what the finding is about), the tracker's own project name
    otherwise (checks 2 and 3, where no kb/ page need exist).

    `item_id` (Gitea #138) is the tracker's own id for the specific item a
    finding is about - set on checks 2 (`waiting_overdue`) and 5
    (`someday_stale`), which each name one item, and `None` on checks 1, 3
    and 4, which are about a whole project rather than one item. It exists so
    `gtd-weekly-review`'s own `task close --id` proposal (option (b) on both
    checks) never has to re-look-up the item by title after the review
    already read it."""

    check: str
    project: str
    message: str
    item_id: Optional[str] = None


@dataclass(frozen=True)
class ReviewReport:
    findings: tuple[Finding, ...]
    checks_run: tuple[str, ...]
    checks_skipped: tuple[tuple[str, str], ...]  # (check, reason)
    kb_project_count: int
    source: Optional[ReadSource]

    @property
    def complete(self) -> bool:
        """Whether every one of the five checks actually ran. `False` is the
        signal `commands.review_cmd` exits 1 on - a partial report must never
        read like a quiet week (see this module's docstring)."""
        return not self.checks_skipped


@dataclass(frozen=True)
class _KbProject:
    title: str
    state: Optional[str]


def _load_kb_projects(kb_dir: Path) -> dict[str, _KbProject]:
    """Every `kb/gtd/` project page, keyed by case-normalized title (#119 D8).
    `page.kind` resolves through the type-spec's own `name:` field
    (`Page.kind`), so this finds a `project` page regardless of which
    `responsibility:` area it lives under."""
    pages = kb_scan.load_kb_pages(kb_dir)
    result: dict[str, _KbProject] = {}
    for page in pages.values():
        if page.kind != "project":
            continue
        result[normalize_project_name(page.title)] = _KbProject(
            title=page.title, state=page.frontmatter.get("state")
        )
    return result


def _weeks_between(start: date, end: date) -> float:
    return (end - start).days / 7


def _months_between(start: date, end: date) -> int:
    """Whole calendar months between two dates, floored - `age_months` for
    check 5. Deliberately calendar-based rather than `days / 30`: an
    approximation would drift a fixed-days threshold away from what "N months"
    actually means at the boundary."""
    months = (end.year - start.year) * 12 + (end.month - start.month)
    if end.day < start.day:
        months -= 1
    return months


def run_review(root: Path, *, today: Optional[date] = None) -> ReviewReport:
    """Run the five weekly-review checks (#119 D10/D26) against the instance
    rooted at `root` and return their findings. Stores nothing (#119 D3): every
    provider read is a fresh call, and no file under `root` is touched.

    Raises `ValidationError` for anything that is not "the provider is
    unreachable right now" - no `.wikitool-tasks.json` at all, or a
    malformed one. Those are configuration problems a retry cannot fix, so
    `commands.review_cmd` reports them as an ordinary exit-1 error rather than
    a partial report.
    """
    today = today if today is not None else date.today()
    cfg = tasks_config.read_config(root)
    if cfg is None:
        raise ValidationError(
            f"No {config.TASKS_CONFIG_FILENAME} - no task tracker is configured, so there is "
            "nothing to join the weekly review against. Configure one first."
        )
    reader = build_reader(cfg)
    kb_projects = _load_kb_projects(Path(root) / "kb")

    try:
        source: Optional[ReadSource] = reader.source()
    except ValidationError:
        # The same read that would answer this has already failed, or is
        # about to below - `source` degrading to `None` here is no worse
        # than the check it would have described also being skipped.
        source = None

    findings: list[Finding] = []
    checks_run: list[str] = []
    checks_skipped: list[tuple[str, str]] = []

    try:
        tracker_projects = reader.projects()
    except ValidationError as exc:
        reason = str(exc)
        checks_skipped.extend((check, reason) for check in _PROJECT_LIST_CHECKS)
        tracker_projects = None

    if tracker_projects is not None:
        open_items_by_key: dict[str, tuple[str, OpenItems]] = {}
        broken_keys: set[str] = set()
        for project in tracker_projects:
            key = normalize_project_name(project.name)
            try:
                open_items_by_key[key] = (project.name, reader.open_items(project.name))
            except ValidationError:
                broken_keys.add(key)

        # Check 1 - stalled: a tracker project with zero open items whose kb/
        # page is `state: active` (#119 D27's anti-noise core: dormant,
        # completed and abandoned never reach here).
        for project in tracker_projects:
            key = normalize_project_name(project.name)
            if key in broken_keys:
                continue
            _, items = open_items_by_key[key]
            if items.count != 0:
                continue
            kb = kb_projects.get(key)
            if kb is not None and kb.state == "active":
                findings.append(Finding(
                    CHECK_STALLED, kb.title,
                    f"Tracker project '{project.name}' has zero open items and the kb/ page "
                    "is state: active.",
                ))
        checks_run.append(CHECK_STALLED)

        # Check 2 - waiting-for overdue: any WAITING item whose follow_up_at
        # is older than the threshold (#119 D9/D30 - never the due date). A
        # WAITING item with no follow_up_at at all is its own finding (D3),
        # not a silent skip - the provider genuinely has nothing to judge
        # staleness against.
        for _key, (name, items) in open_items_by_key.items():
            for item in items.waiting:
                if item.follow_up_at is None:
                    findings.append(Finding(
                        CHECK_WAITING_NO_FOLLOWUP, name,
                        f"'{item.title}' is WAITING but has no follow_up_at - cannot judge "
                        "whether it is overdue.",
                        item_id=item.id,
                    ))
                    continue
                age_days = (today - item.follow_up_at).days
                if age_days > cfg.thresholds.stalled_waiting_days:
                    findings.append(Finding(
                        CHECK_WAITING_OVERDUE, name,
                        f"'{item.title}' is {age_days} day(s) past its follow_up_at "
                        f"({item.follow_up_at.isoformat()}).",
                        item_id=item.id,
                    ))
        checks_run.append(CHECK_WAITING_OVERDUE)

        # Check 3 - tracker project with no kb/ page, older than the
        # threshold (#119 D26's noise brake: an age threshold, not a marker).
        # A project with no determinable creation date is its own finding
        # (D3), not a silent skip - check 3 cannot judge its age either way.
        for project in tracker_projects:
            key = normalize_project_name(project.name)
            if key in kb_projects:
                continue
            if project.created is None:
                findings.append(Finding(
                    CHECK_PROJECT_AGE_UNKNOWN, project.name,
                    "No creation date available for this tracker project - cannot judge "
                    "whether it needs a kb/ page yet.",
                ))
                continue
            age_weeks = _weeks_between(project.created, today)
            if age_weeks > cfg.thresholds.unpaged_project_weeks:
                findings.append(Finding(
                    CHECK_UNPAGED_PROJECT, project.name,
                    f"No kb/ page for this tracker project after {age_weeks:.1f} week(s) "
                    f"(created {project.created.isoformat()}).",
                ))
        checks_run.append(CHECK_UNPAGED_PROJECT)

        # Check 4 - kb/ page with no open loop: `state: active` but either no
        # tracker project of this name exists, or it has zero open items. This
        # is the reverse direction of check 3's join (#119 D8's beidseitig
        # unmatched report - a rename on either side must surface somewhere).
        tracker_by_key = {normalize_project_name(p.name): p for p in tracker_projects}
        for key, kb in kb_projects.items():
            if kb.state != "active":
                continue
            project = tracker_by_key.get(key)
            if project is None:
                findings.append(Finding(
                    CHECK_NO_OPEN_LOOP, kb.title,
                    "state: active, but no tracker project of this name exists.",
                ))
                continue
            if key in broken_keys:
                continue
            _, items = open_items_by_key[key]
            if items.count == 0:
                findings.append(Finding(
                    CHECK_NO_OPEN_LOOP, kb.title,
                    f"state: active, but tracker project '{project.name}' has zero open items.",
                ))
        checks_run.append(CHECK_NO_OPEN_LOOP)

    # Check 5 - someday/maybe items untouched for longer than the threshold.
    # Independent of the tracker project list, so it still runs when
    # `projects()` above failed but `someday_items()` does not.
    try:
        someday = reader.someday_items()
    except ValidationError as exc:
        checks_skipped.append((CHECK_SOMEDAY_STALE, str(exc)))
    else:
        for item in someday:
            if item.modified is None:
                continue
            age_months = _months_between(item.modified, today)
            if age_months > cfg.thresholds.someday_stale_months:
                findings.append(Finding(
                    CHECK_SOMEDAY_STALE, item.title,
                    f"Untouched for {age_months} month(s) (last modified "
                    f"{item.modified.isoformat()}).",
                    item_id=item.id,
                ))
        checks_run.append(CHECK_SOMEDAY_STALE)

    return ReviewReport(
        findings=tuple(findings),
        checks_run=tuple(checks_run),
        checks_skipped=tuple(checks_skipped),
        kb_project_count=len(kb_projects),
        source=source,
    )