"""Versioned, site-scoped reusable blocks with opt-in, draft-only propagation.

Published pages are NEVER rewritten by a shared-component update. A linked
instance is a validated, materialized block with shared_ref metadata. Updates
require a fresh preview token, exact page revision and an unmodified instance.
"""
from __future__ import annotations
import copy
import hashlib
import json
import re
import uuid
from fastapi import APIRouter, Body, HTTPException, Request
from . import db, enterprise, blueprints, studio_v86
from .core import uid

router=APIRouter(prefix='/api/sites',tags=['Reusable Components'])


def canonical(value):
    return json.dumps(value,ensure_ascii=False,sort_keys=True,separators=(',',':'))


def _content(block):
    """Content fingerprint independent of generated instance IDs and provenance."""
    def strip(item):
        if isinstance(item,dict):return {k:strip(v) for k,v in item.items() if k not in ('id','shared_ref')}
        if isinstance(item,list):return [strip(v) for v in item]
        return item
    return strip(block)


def fingerprint(block):
    return hashlib.sha256(canonical(_content(block)).encode()).hexdigest()


def setup():
    with db.connect() as c:
        c.executescript('''CREATE TABLE IF NOT EXISTS reusable_components(
          id TEXT PRIMARY KEY,site_id TEXT NOT NULL REFERENCES sites(id) ON DELETE CASCADE,
          name TEXT NOT NULL,version INTEGER NOT NULL DEFAULT 1,block_json TEXT NOT NULL,
          updated_at TEXT NOT NULL);
          CREATE INDEX IF NOT EXISTS idx_reuse_site ON reusable_components(site_id);
          CREATE TABLE IF NOT EXISTS reusable_component_versions(
            component_id TEXT NOT NULL REFERENCES reusable_components(id) ON DELETE CASCADE,
            version INTEGER NOT NULL,block_json TEXT NOT NULL,snapshot_hash TEXT NOT NULL,
            created_at TEXT NOT NULL,PRIMARY KEY(component_id,version));
        ''')
        # Safe additive migration of old version-1 reusable blocks.
        legacy=c.execute('SELECT id,version,block_json,updated_at FROM reusable_components').fetchall()
        for row in legacy:
            block=json.loads(row['block_json'])
            c.execute('''INSERT INTO reusable_component_versions
                 (component_id,version,block_json,snapshot_hash,created_at)
                 VALUES(?,?,?,?,?) ON CONFLICT(component_id,version) DO NOTHING''',
                 (row['id'],row['version'],row['block_json'],fingerprint(block),row['updated_at']))


def _component(site_id,component_id,c=None):
    sql='SELECT * FROM reusable_components WHERE site_id=? AND id=?'
    row=c.execute(sql,(site_id,component_id)).fetchone() if c else db.one(sql,(site_id,component_id))
    if not row:raise HTTPException(404,'本站组件不存在')
    return dict(row)


def _validate_block(block):
    try:
        validated=blueprints.validate_blocks([block])[0]
    except (ValueError,TypeError) as exc:raise HTTPException(400,str(exc))
    # A library source is an independent snapshot. Embedded source links are
    # removed recursively; only insertion as a linked instance adds provenance.
    def detach(node):
        node.pop('shared_ref',None)
        if node.get('type')=='layout':
            for col in node.get('columns',[]):
                for sub in col.get('blocks',[]):detach(sub)
    detach(validated)
    return validated


def _name(value):
    name=str(value or '').strip()
    if not name or len(name)>100:raise HTTPException(400,'组件名称需要1–100个字符')
    return name


def versions(site_id,component_id):
    _component(site_id,component_id)
    rows=db.rows('''SELECT version,snapshot_hash,created_at FROM reusable_component_versions
       WHERE component_id=? ORDER BY version DESC''',(component_id,))
    return {'items':rows}


@router.get('/{site_id}/components')
def all_components(request:Request,site_id:str):
    enterprise.require(request,site_id,'viewer')
    return [{**r,'block':json.loads(r['block_json']), 'snapshot_hash':fingerprint(json.loads(r['block_json']))}
       for r in db.rows('SELECT * FROM reusable_components WHERE site_id=? ORDER BY updated_at DESC',(site_id,))]


@router.post('/{site_id}/components')
def save_component(request:Request,site_id:str,payload:dict=Body(...)):
    enterprise.require(request,site_id,'editor')
    name=_name(payload.get('name'))
    block=_validate_block(payload.get('block'))
    # Saved library snapshots must not retain a reference to a different component.
    block.pop('shared_ref',None)
    cid=uid();now=db.now();encoded=canonical(block);sha=fingerprint(block)
    with db.connect() as c:
        c.execute('INSERT INTO reusable_components VALUES (?,?,?,?,?,?)',(cid,site_id,name,1,encoded,now))
        c.execute('INSERT INTO reusable_component_versions VALUES (?,?,?,?,?)',(cid,1,encoded,sha,now))
    return {'id':cid,'name':name,'version':1,'block':block,'snapshot_hash':sha}


@router.put('/{site_id}/components/{component_id}')
def update_component(request:Request,site_id:str,component_id:str,payload:dict=Body(...)):
    enterprise.require(request,site_id,'editor')
    block=_validate_block(payload.get('block'));block.pop('shared_ref',None)
    with db.connect() as c:
        row=_component(site_id,component_id,c)
        rev=payload.get('expected_version')
        if type(rev) is not int or rev!=row['version']:raise HTTPException(409,'组件版本已改变，请重新加载')
        version=rev+1;name=_name(payload.get('name') if payload.get('name') is not None else row['name'])
        encoded=canonical(block);now=db.now()
        cur=c.execute('''UPDATE reusable_components SET name=?,block_json=?,version=?,updated_at=?
              WHERE id=? AND site_id=? AND version=?''',(name,encoded,version,now,component_id,site_id,rev))
        if cur.rowcount!=1:raise HTTPException(409,'组件已由其他用户修改')
        c.execute('INSERT INTO reusable_component_versions VALUES (?,?,?,?,?)',
           (component_id,version,encoded,fingerprint(block),now))
    return {'id':component_id,'version':version,'snapshot_hash':fingerprint(block),'published_unchanged':True}


@router.delete('/{site_id}/components/{component_id}')
def delete_component(request:Request,site_id:str,component_id:str):
    enterprise.require(request,site_id,'editor')
    _component(site_id,component_id)
    # Reject deletion while linked instances exist; preserve historical versions.
    if _references(site_id,component_id):raise HTTPException(409,'组件仍被页面引用，请先解除引用')
    db.execute('DELETE FROM reusable_components WHERE site_id=? AND id=?',(site_id,component_id))
    return {'deleted':True}


@router.get('/{site_id}/components/{component_id}/versions')
def api_versions(request:Request,site_id:str,component_id:str):
    enterprise.require(request,site_id,'viewer')
    return versions(site_id,component_id)


@router.get('/{site_id}/components/{component_id}/versions/{version}')
def api_version(request:Request,site_id:str,component_id:str,version:int):
    enterprise.require(request,site_id,'viewer')
    _component(site_id,component_id)
    row=db.one('SELECT * FROM reusable_component_versions WHERE component_id=? AND version=?',(component_id,version))
    if not row:raise HTTPException(404,'版本不存在')
    block=json.loads(row['block_json'])
    if fingerprint(block)!=row['snapshot_hash']:raise HTTPException(409,'历史快照完整性校验失败')
    return {'version':version,'block':block,'snapshot_hash':row['snapshot_hash']}


def _walk(rows):
    for block in rows:
        yield block
        if block.get('type')=='layout':
            for col in block.get('columns',[]):yield from _walk(col.get('blocks',[]))


def _replace_in_tree(rows,block_id,replacement):
    for i,block in enumerate(rows):
        if block.get('id')==block_id:
            rows[i]=replacement;return True
        if block.get('type')=='layout':
            for col in block.get('columns',[]):
                if _replace_in_tree(col['blocks'],block_id,replacement):return True
    return False


def _references(site_id,component_id):
    # Bounded scan; site ownership is enforced at query boundary.
    all_pages=db.rows('SELECT * FROM entries WHERE site_id=?',(site_id,))
    drafts={r['entry_id']:r for r in db.rows('SELECT * FROM studio_drafts WHERE site_id=?',(site_id,))}
    found=[]
    for page in all_pages:
        draft=drafts.get(page['id'])
        plan=json.loads(draft['blueprint_json']) if draft else json.loads(page['meta_json'] or '{}')
        for block in _walk(plan.get('blocks',[])):
            meta=block.get('shared_ref')
            if isinstance(meta,dict) and meta.get('id')==component_id:
                found.append({'entry_id':page['id'],'route':page['route'],'title':page['title'],
                    'block_id':block['id'],'current_version':meta.get('version'),
                    'local_modified':fingerprint(block)!=meta.get('hash'),
                    'draft_revision':draft['revision'] if draft else 0,
                    'base_hash':draft['base_hash'] if draft else studio_v86._hash(page),
                    'has_draft':bool(draft),'conflict':bool(draft and draft['base_hash']!=studio_v86._hash(page))})
    return found


def _preview(site_id,component_id):
    component=_component(site_id,component_id)
    refs=_references(site_id,component_id)
    for item in refs:
        item['up_to_date']=item['current_version']==component['version']
        item['eligible']=not item['local_modified'] and not item['conflict'] and not item['up_to_date']
        item['reason']=('存在页面发布冲突' if item['conflict'] else '页面有本地修改' if item['local_modified']
                        else '已是最新版' if item['up_to_date'] else '')
    # Token includes all page revisions and instance fingerprints; replay of stale
    # preview after any page or component changes is rejected.
    proof={'component':component_id,'version':component['version'],'references':refs}
    token=hashlib.sha256(canonical(proof).encode()).hexdigest()
    return {'component':{'id':component_id,'name':component['name'],'version':component['version']},
            'references':refs,'plan_token':token,'warning':'同步仅写入新草稿，不自动发布或部署'}


@router.get('/{site_id}/components/{component_id}/usage')
def api_usage(request:Request,site_id:str,component_id:str):
    enterprise.require(request,site_id,'viewer')
    return _preview(site_id,component_id)


def _copy_into(snapshot,original,component_id,version):
    block=copy.deepcopy(snapshot)
    def fresh(node,root=False):
        node['id']=original['id'] if root else uuid.uuid4().hex[:10]
        node.pop('shared_ref',None)
        if node.get('type')=='layout':
            for col in node.get('columns',[]):
                for sub in col.get('blocks',[]):fresh(sub)
    fresh(block,True)
    block['shared_ref']={'id':component_id,'version':version,'hash':fingerprint(block)}
    return block


@router.post('/{site_id}/components/{component_id}/sync')
def api_sync(request:Request,site_id:str,component_id:str,payload:dict=Body(...)):
    enterprise.require(request,site_id,'editor')
    selected=payload.get('entry_ids')
    if not isinstance(selected,list) or not selected or len(selected)>100 or len(set(selected))!=len(selected) or any(not isinstance(s,str) for s in selected):
        raise HTTPException(400,'选择1–100个不同页面')
    preview=_preview(site_id,component_id)
    if payload.get('plan_token')!=preview['plan_token']:raise HTTPException(409,'预检已过期，请重新查看引用页面')
    chosen=set(selected)
    available={r['entry_id'] for r in preview['references'] if r['eligible']}
    if not chosen.issubset(available):raise HTTPException(409,'包含已修改、存在冲突或不可同步的页面')
    component=_component(site_id,component_id)
    current=blueprints.validate_blocks([json.loads(component['block_json'])])[0]
    # Restrict to exactly one linked instance per page per request for now.
    # When one page has multiple references, sync all eligible instances atomically.
    updated=[]
    expected_pages={r['entry_id']:(r['draft_revision'],r['base_hash']) for r in preview['references'] if r['entry_id'] in chosen}
    with db.connect() as c:
        # Lock the read/compare/write window. PostgreSQL uses an advisory
        # transaction lock through the compatibility adapter.
        c.execute('BEGIN IMMEDIATE')
        newest=_component(site_id,component_id,c)
        if newest['version']!=component['version']:
            raise HTTPException(409,'组件源版本发生变化')
        for entry_id in selected:
            page=c.execute('SELECT * FROM entries WHERE site_id=? AND id=?',(site_id,entry_id)).fetchone()
            if not page:raise HTTPException(409,'页面已删除，请重新预检')
            draft=c.execute('SELECT * FROM studio_drafts WHERE site_id=? AND entry_id=?',(site_id,entry_id)).fetchone()
            old_hash=studio_v86._hash(dict(page))
            expected_page_revision,expected_base=expected_pages[entry_id]
            if expected_base!=old_hash or (draft['revision'] if draft else 0)!=expected_page_revision:
                raise HTTPException(409,'页面版本已变化，重新预检后同步')
            if draft and draft['base_hash']!=old_hash:raise HTTPException(409,'页面内容已变化')
            plan=json.loads(draft['blueprint_json']) if draft else {
                'blocks':json.loads(page['meta_json'] or '{}').get('blocks',[]),
                'page_template':json.loads(page['meta_json'] or '{}').get('page_template','home' if page['route']=='/' else 'standard'),
                'layout_mode':json.loads(page['meta_json'] or '{}').get('layout_mode','append')}
            did=0
            for block in list(_walk(plan['blocks'])):
                ref=block.get('shared_ref')
                if isinstance(ref,dict) and ref.get('id')==component_id:
                    if fingerprint(block)!=ref.get('hash') or ref.get('version')==component['version']:
                        raise HTTPException(409,'引用发生变化，请重新预检')
                    if not _replace_in_tree(plan['blocks'],block['id'],_copy_into(current,block,component_id,component['version'])):
                        raise HTTPException(409,'组件位置发生变化')
                    did+=1
            if not did:raise HTTPException(409,'页面已经没有组件引用')
            plan=studio_v86._validate(plan)
            expected=draft['revision'] if draft else 0
            rev=expected+1
            if draft:
                cur=c.execute('''UPDATE studio_drafts SET revision=?,blueprint_json=?,updated_at=?
                  WHERE site_id=? AND entry_id=? AND revision=? AND base_hash=?''',
                  (rev,canonical(plan),db.now(),site_id,entry_id,expected,draft['base_hash']))
                if cur.rowcount!=1:raise HTTPException(409,'草稿并发冲突')
            else:
                c.execute('INSERT INTO studio_drafts VALUES (?,?,?,?,?,?)',
                  (site_id,entry_id,rev,old_hash,canonical(plan),db.now()))
            studio_v86._journal(c,site_id,entry_id,rev,'draft',plan,enterprise.actor(request))
            updated.append({'entry_id':entry_id,'revision':rev,'instances':did})
    return {'updated':updated,'published_unchanged':True,'build_required_after_publish':True}