"""Merge request tag view helpers and fast-forward merge endpoint."""

from __future__ import annotations

import json
from typing import Any
from urllib.parse import quote

import pygit2
from fastapi import APIRouter, Depends, Form, HTTPException, Query
from fastapi.responses import HTMLResponse, RedirectResponse, Response

from pygittools.merge import MergeRequest, MergeRequestStatus, get_merge_request_by_oid
from pygitweb.auth import require_active_user_if_auth_enabled
from pygitweb.config import settings
from pygitweb.git_helpers import open_repo
from pygitweb.tasks import _validate_project
from pygitweb.templates_env import POSTAMBLE, PREAMBLE, env, jinja_escape
from pygitweb.validation import is_valid_ref_format


def _branch_short_name(ref: str) -> str:
	return ref.removeprefix("refs/heads/") if ref.startswith("refs/heads/") else ref


merge_router = APIRouter(tags=["merge_requests"], dependencies=[Depends(require_active_user_if_auth_enabled)])

_STATUS_LABELS: dict[MergeRequestStatus, str] = {
	MergeRequestStatus.CAN_FAST_FORWARD: "Can fast-forward",
	MergeRequestStatus.UP_TO_DATE: "Already up to date",
	MergeRequestStatus.BLOCKED_DIVERGED: "Blocked: histories diverged (not fast-forward)",
	MergeRequestStatus.OURS_REF_MISSING: "Blocked: ours ref is missing",
	MergeRequestStatus.MR_HEAD_MISSING: "Blocked: merge request head is missing from the repository",
}


def try_merge_request_from_tag(repo: pygit2.Repository, tag: pygit2.Tag) -> MergeRequest | None:
	try:
		return get_merge_request_by_oid(repo, tag.id)
	except (ValueError, json.JSONDecodeError, TypeError, KeyError):
		return None


def resolve_merge_request_tag_to_tip(
	repo: pygit2.Repository, obj: pygit2.Tag
) -> tuple[pygit2.Tag, MergeRequest] | None:
	"""If ``obj`` is an MR tag and ``refs/tags/mr/…`` points to a newer tag object, return that tip."""
	mr = try_merge_request_from_tag(repo, obj)
	if mr is None:
		return None
	if mr.name not in repo.references:
		return obj, mr
	tip_id = repo.references[mr.name].resolve().target
	if tip_id == obj.id:
		return obj, mr
	tip_obj = repo[tip_id]
	if not isinstance(tip_obj, pygit2.Tag):
		return obj, mr
	mr_tip = try_merge_request_from_tag(repo, tip_obj)
	if mr_tip is None:
		return obj, mr
	return tip_obj, mr_tip


def merge_request_status_fields(repo: pygit2.Repository, mr: MergeRequest) -> dict[str, Any]:
	try:
		status = mr.check_status(repo)
	except ValueError as exc:
		return {
			"status_code": "error",
			"status_label": "Unable to analyze merge",
			"status_detail": str(exc),
			"show_merge_button": False,
		}
	label = _STATUS_LABELS.get(status, status.value)
	return {
		"status_code": status.value,
		"status_label": label,
		"status_detail": "",
		"show_merge_button": status == MergeRequestStatus.CAN_FAST_FORWARD,
	}


def _head_view_url(project: str, repo: pygit2.Repository, head_hex: str) -> tuple[str, str]:
	try:
		oid = pygit2.Oid(hex=head_hex)
		obj = repo[oid]
	except (KeyError, ValueError, TypeError):
		return head_hex[:7], ""
	t = getattr(obj, "type_str", "") or ""
	short = head_hex[:7]
	if t == "commit":
		return short, f"/project/{project}?a=commit&h={quote(head_hex, safe='')}"
	if t == "tag":
		return short, f"/project/{project}?a=tag&h={quote(head_hex, safe='')}"
	return short, ""


def merge_request_tag_response(
	project: str,
	repo: pygit2.Repository,
	mr: MergeRequest,
	tag_name: str,
	tag_oid: str,
	tagger: str,
	tagger_date: str,
) -> Response:
	new_oid = mr.refresh_from_theirs(repo)
	if new_oid is not None:
		return RedirectResponse(
			url=f"/project/{project}?a=tag&h={quote(str(new_oid), safe='')}",
			status_code=302,
		)

	status_fields = merge_request_status_fields(repo, mr)
	head_short, head_url = _head_view_url(project, repo, str(mr.target))
	ours_ref = mr.ours
	ours_url = f"/project/{project}?a=log&h={quote(ours_ref, safe='')}"
	theirs_ref = mr.theirs or ""
	theirs_url = f"/project/{project}?a=log&h={quote(theirs_ref, safe='')}" if mr.theirs else ""

	comments_rows: list[tuple[str, str]] = []
	for c in mr.comments:
		ch = str(c)
		comments_rows.append((ch[:7], f"/project/{project}?a=tag&h={quote(ch, safe='')}"))

	current_tag_oid = str(repo.references[mr.name].resolve().target)

	ctx = {
		"project": project,
		"project_url": f"/project/{project}",
		"tag_name": tag_name,
		"tag_oid": current_tag_oid,
		"tag_view_url": f"/project/{project}?a=tag&h={quote(current_tag_oid, safe='')}",
		"mr_title": mr.title,
		"mr_description": mr.description or "",
		"ours_ref": ours_ref,
		"ours_url": ours_url,
		"theirs_ref": theirs_ref,
		"theirs_url": theirs_url,
		"head_short": head_short,
		"head_url": head_url,
		"head_full": str(mr.target),
		"tagger": tagger,
		"tagger_date": tagger_date,
		"opener": str(mr.opener),
		"created_at": mr.created_at.isoformat() if mr.created_at else "",
		"updated_at": mr.updated_at.isoformat() if mr.updated_at else "",
		"comments": comments_rows,
		"merge_action_url": f"/mr/ff?project={quote(project, safe='')}&h={quote(current_tag_oid, safe='')}",
		**status_fields,
	}
	title = f"Merge request: {jinja_escape(mr.title) or ''} — {jinja_escape(project) or ''}"
	pre = PREAMBLE.render(title=title, site_name=settings.SITE_NAME)
	body = env.get_template("merge_request_tag.html").render(**ctx)
	return HTMLResponse(f"{pre}{body}{POSTAMBLE}")


@merge_router.post("/create")
def merge_request_create(
	project: str = Form(...),
	theirs: str = Form(...),
	ours: str = Form(...),
	title: str = Form(""),
) -> RedirectResponse:
	_validate_project(project)
	theirs_ref = theirs.strip()
	ours_ref = ours.strip()
	if not theirs_ref or not ours_ref:
		raise HTTPException(status_code=400, detail="theirs and ours are required")
	if not is_valid_ref_format(theirs_ref) or not is_valid_ref_format(ours_ref):
		raise HTTPException(status_code=400, detail="Invalid ref format")
	repo = open_repo(project)
	try:
		theirs_tip = repo.revparse_single(theirs_ref).peel(pygit2.Commit).id
	except (KeyError, ValueError, pygit2.GitError) as exc:
		raise HTTPException(status_code=404, detail=f"Cannot resolve theirs ref {theirs_ref!r}") from exc
	try:
		repo.revparse_single(ours_ref)
	except (KeyError, ValueError, pygit2.GitError) as exc:
		raise HTTPException(status_code=404, detail=f"Cannot resolve ours ref {ours_ref!r}") from exc
	opener = repo.default_signature
	t = title.strip()
	if not t:
		t = f"Merge {_branch_short_name(theirs_ref)} into {_branch_short_name(ours_ref)}"
	mr = MergeRequest(
		target=theirs_tip,
		opener=opener,
		ours=ours_ref,
		theirs=theirs_ref,
		title=t,
		description="",
	)
	oid = mr.write(repo)
	dest = f"/project/{project}?a=tag&h={quote(str(oid), safe='')}"
	return RedirectResponse(url=dest, status_code=303)


@merge_router.post("/ff")
def merge_fast_forward(
	project: str = Query(..., description="Project path"),
	h: str = Query(..., description="Annotated tag object id (hex)"),
) -> RedirectResponse:
	_validate_project(project)
	if not h or not is_valid_ref_format(h):
		raise HTTPException(status_code=400, detail="Invalid tag hash (h)")
	repo = open_repo(project)
	try:
		obj = repo.revparse_single(h)
	except (KeyError, pygit2.GitError, OSError) as exc:
		raise HTTPException(status_code=404, detail="Tag not found") from exc
	if not isinstance(obj, pygit2.Tag):
		raise HTTPException(status_code=400, detail="Not an annotated tag")
	resolved = resolve_merge_request_tag_to_tip(repo, obj)
	if resolved is None:
		raise HTTPException(status_code=400, detail="Not a merge request tag")
	obj, mr = resolved
	mr.refresh_from_theirs(repo)
	try:
		mr.merge(repo)
	except ValueError as exc:
		raise HTTPException(status_code=400, detail=str(exc)) from exc
	tag_oid = str(repo.references[mr.name].resolve().target)
	dest = f"/project/{project}?a=tag&h={quote(tag_oid, safe='')}"
	return RedirectResponse(url=dest, status_code=303)