"""Early duplicate-work detection for author work-issue sessions (#400)."""

from __future__ import annotations

from typing import Any, Mapping

import issue_claim_heartbeat as claim_hb

PHASE_LOCK = "lock_issue"
PHASE_COMMIT = "commit"
PHASE_PUSH = "push"
PHASE_CREATE_PR = "create_pr"

OUTCOME_DUPLICATE_PR_PREVENTED = "duplicate_pr_prevented"
OUTCOME_DUPLICATE_BRANCH_PREVENTED = "duplicate_branch_prevented"
OUTCOME_DUPLICATE_COMMIT_PREVENTED = "duplicate_commit_prevented"
OUTCOME_DUPLICATE_WORK_NOT_PREVENTED = "duplicate_work_not_prevented"

_ACTIVE_CLAIM_STATUSES = frozenset({"active", "awaiting_review"})


def _issue_pattern(issue_number: int) -> str:
    return f"issue-{int(issue_number)}"


def _linked_open_pr(issue_number: int, open_prs: list[dict]) -> dict | None:
    return claim_hb._linked_open_pr(issue_number, open_prs)


def _pr_links_issue(issue_number: int, pr: Mapping[str, Any]) -> bool:
    """Same linkage rule ``claim_hb._linked_open_pr`` applies, per PR.

    ``_linked_open_pr`` only yields the *first* match, which cannot answer
    "is there exactly one linked PR?" — a question the owning-PR exemption
    below must answer before it can trust any of them.
    """
    pattern = _issue_pattern(issue_number)
    head = (pr.get("head") or {}).get("ref") or ""
    text = f"{pr.get('title', '')} {pr.get('body', '')}".lower()
    if pattern in head.lower():
        return True
    return (
        f"closes #{int(issue_number)}" in text
        or f"fixes #{int(issue_number)}" in text
    )


def _all_linked_open_prs(
    issue_number: int, open_prs: list[dict]
) -> list[Mapping[str, Any]]:
    return [pr for pr in (open_prs or []) if _pr_links_issue(issue_number, pr)]


def _assess_owning_pr_exemption(
    issue_number: int,
    *,
    linked_open_prs: list[Mapping[str, Any]],
    locked_branch: str | None,
    recovered_owning_pr: Mapping[str, Any] | None,
) -> tuple[bool, list[str]]:
    """Is the linked open PR provably the one a sanctioned recovery owns (#755)?

    ``recovered_owning_pr`` is produced by
    ``issue_lock_recovery.owning_pr_recovery_evidence`` from a completed
    server-side recovery assessment — it is never a caller-supplied field.
    Every element is re-checked here against the live PR list this gate was
    given, so a stale or partial token cannot widen the exemption.

    Returns ``(exempt, diagnostic_reasons)``. Diagnostics are only emitted when
    a token was offered and rejected, so a blocked caller can see which element
    of ownership disagreed.
    """
    if not recovered_owning_pr:
        return False, []

    notes: list[str] = []
    token_issue = recovered_owning_pr.get("issue_number")
    token_pr = recovered_owning_pr.get("pr_number")
    token_branch = str(recovered_owning_pr.get("branch_name") or "").strip()
    token_head = str(recovered_owning_pr.get("head_sha") or "").strip()
    locked = (locked_branch or "").strip()

    if token_issue is not None and int(token_issue) != int(issue_number):
        notes.append(
            f"recovery evidence is for issue #{token_issue}, not "
            f"#{issue_number} (no owning-PR exemption)"
        )
        return False, notes
    if not locked or not token_branch or locked != token_branch:
        notes.append(
            f"recovery evidence branch '{token_branch or 'unknown'}' does not "
            f"match the branch being locked '{locked or 'unknown'}' "
            "(no owning-PR exemption)"
        )
        return False, notes
    if len(linked_open_prs) != 1:
        numbers = ", ".join(
            f"#{pr.get('number')}" for pr in linked_open_prs
        ) or "none"
        notes.append(
            f"{len(linked_open_prs)} open PRs link issue #{issue_number} "
            f"({numbers}); recovery may only own exactly one "
            "(no owning-PR exemption)"
        )
        return False, notes

    only = linked_open_prs[0]
    head_obj = only.get("head") or {}
    only_number = only.get("number")
    only_ref = str(head_obj.get("ref") or "").strip()
    only_sha = str(head_obj.get("sha") or "").strip()

    if token_pr is None or only_number is None or int(only_number) != int(token_pr):
        notes.append(
            f"linked open PR #{only_number} is not the recovered owning PR "
            f"#{token_pr} (no owning-PR exemption)"
        )
        return False, notes
    if only_ref != token_branch:
        notes.append(
            f"open PR #{only_number} head branch '{only_ref}' does not match "
            f"the recovered branch '{token_branch}' (no owning-PR exemption)"
        )
        return False, notes
    if not token_head or not only_sha or only_sha != token_head:
        notes.append(
            f"open PR #{only_number} head {only_sha or 'unknown'} does not "
            f"match the recovered head {token_head or 'unknown'} "
            "(no owning-PR exemption)"
        )
        return False, notes

    return True, [
        f"open PR #{only_number} is the exact PR already owned by the "
        f"recovering lock for issue #{issue_number} (branch '{token_branch}', "
        f"head {token_head}); not duplicate work"
    ]


def _matching_branches(
    issue_number: int,
    branch_names: list[str],
    *,
    locked_branch: str | None = None,
) -> list[str]:
    pattern = _issue_pattern(issue_number)
    matches = [
        name for name in (branch_names or [])
        if pattern in (name or "").lower()
    ]
    if locked_branch:
        locked = locked_branch.strip()
        matches = [name for name in matches if name != locked]
    return matches


def assess_work_issue_duplicate_gate(
    issue_number: int,
    *,
    open_prs: list[dict] | None = None,
    branch_names: list[str] | None = None,
    claim_entry: dict | None = None,
    locked_branch: str | None = None,
    phase: str = PHASE_LOCK,
    recovered_owning_pr: Mapping[str, Any] | None = None,
) -> dict[str, Any]:
    """Fail closed when duplicate work is already in flight for an issue.

    ``recovered_owning_pr`` (#755) is server-derived evidence that a sanctioned
    dead-session lock recovery already owns one specific open PR. It exempts
    *only* that exact PR from the linked-open-PR blocker; every other duplicate
    signal, and every mismatch, keeps failing closed.
    """
    reasons: list[str] = []
    outcome = OUTCOME_DUPLICATE_WORK_NOT_PREVENTED
    prs = list(open_prs or [])
    branches = list(branch_names or [])
    pattern = _issue_pattern(issue_number)

    linked = _linked_open_pr(issue_number, prs)
    linked_open_prs = _all_linked_open_prs(issue_number, prs)
    owning_pr_exempted = False
    exemption_notes: list[str] = []
    if linked:
        owning_pr_exempted, exemption_notes = _assess_owning_pr_exemption(
            issue_number,
            linked_open_prs=linked_open_prs,
            locked_branch=locked_branch,
            recovered_owning_pr=recovered_owning_pr,
        )
        if not owning_pr_exempted:
            reasons.append(
                f"open PR #{linked.get('number')} already covers issue "
                f"#{issue_number} (fail closed)"
            )
            reasons.extend(exemption_notes)
            outcome = OUTCOME_DUPLICATE_PR_PREVENTED

    conflicting_branches = _matching_branches(
        issue_number, branches, locked_branch=locked_branch
    )
    if conflicting_branches:
        names = ", ".join(conflicting_branches[:5])
        reasons.append(
            f"remote branch(es) already match issue pattern '{pattern}': "
            f"{names} (fail closed)"
        )
        if outcome == OUTCOME_DUPLICATE_WORK_NOT_PREVENTED:
            outcome = OUTCOME_DUPLICATE_BRANCH_PREVENTED

    entry = claim_entry or {}
    if entry.get("linked_open_pr") and not linked:
        reasons.append(
            f"claim inventory reports open PR #{entry['linked_open_pr']} "
            f"for issue #{issue_number} (fail closed)"
        )
        outcome = OUTCOME_DUPLICATE_PR_PREVENTED

    status = (entry.get("status") or "").strip().lower()
    if status in _ACTIVE_CLAIM_STATUSES and not linked:
        heartbeat = entry.get("latest_heartbeat") or {}
        claim_branch = (heartbeat.get("branch") or "").strip()
        if locked_branch and claim_branch and claim_branch != locked_branch:
            reasons.append(
                f"active claim lease on branch '{claim_branch}' blocks "
                f"work on '{locked_branch}' for issue #{issue_number} "
                "(fail closed)"
            )
            if outcome == OUTCOME_DUPLICATE_WORK_NOT_PREVENTED:
                outcome = OUTCOME_DUPLICATE_BRANCH_PREVENTED
        elif not locked_branch and status == "active":
            reasons.append(
                f"issue #{issue_number} has an active claim lease "
                "(fail closed)"
            )
            if outcome == OUTCOME_DUPLICATE_WORK_NOT_PREVENTED:
                outcome = OUTCOME_DUPLICATE_BRANCH_PREVENTED

    if phase in {PHASE_COMMIT, PHASE_PUSH} and reasons:
        if outcome == OUTCOME_DUPLICATE_PR_PREVENTED:
            outcome = OUTCOME_DUPLICATE_COMMIT_PREVENTED
        elif outcome == OUTCOME_DUPLICATE_BRANCH_PREVENTED:
            outcome = OUTCOME_DUPLICATE_COMMIT_PREVENTED

    block = bool(reasons)
    return {
        "block": block,
        "performed": not block,
        "issue_number": issue_number,
        "phase": phase,
        "outcome": outcome,
        "linked_open_pr": linked.get("number") if linked else entry.get("linked_open_pr"),
        "linked_open_pr_count": len(linked_open_prs),
        "owning_pr_recovery_exempted": owning_pr_exempted,
        "owning_pr_recovery_notes": list(exemption_notes),
        "conflicting_branches": conflicting_branches,
        "claim_status": status or None,
        "reasons": reasons,
        "safe_next_action": (
            "stop before mutating; preserve local work and produce a "
            "reconciliation handoff if a concurrent PR appeared after push"
            if block and phase == PHASE_CREATE_PR
            else "stop before mutating; do not commit or push duplicate work"
            if block
            else "proceed"
        ),
    }


def assess_work_issue_duplicate_report(report_text: str) -> dict[str, Any]:
    """Require explicit duplicate-work outcome wording in work-issue reports."""
    text = (report_text or "").lower()
    markers = {
        OUTCOME_DUPLICATE_PR_PREVENTED: (
            "duplicate pr prevented",
            "duplicate_pr_prevented",
        ),
        OUTCOME_DUPLICATE_BRANCH_PREVENTED: (
            "duplicate branch prevented",
            "duplicate_branch_prevented",
        ),
        OUTCOME_DUPLICATE_COMMIT_PREVENTED: (
            "duplicate commit prevented",
            "duplicate_commit_prevented",
        ),
        OUTCOME_DUPLICATE_WORK_NOT_PREVENTED: (
            "duplicate work not prevented",
            "duplicate_work_not_prevented",
            "no duplicate work",
        ),
    }
    matched = [
        key for key, phrases in markers.items()
        if any(phrase in text for phrase in phrases)
    ]
    if len(matched) != 1:
        return {
            "complete": False,
            "downgraded": True,
            "reasons": [
                "work-issue report must state exactly one duplicate-work "
                "outcome (duplicate PR/branch/commit prevented, or "
                "duplicate work not prevented)"
            ],
        }
    return {
        "complete": True,
        "downgraded": False,
        "outcome": matched[0],
        "reasons": [],
    }