"""Validated per-device static CSS for pages and nested layout grids.

Uses exact IDs from validate_blocks, never user supplied CSS selectors/expressions.
Desktop structure is preserved; tablet and mobile may have distinct spans/order.
"""
import re,json,hashlib
from .blueprints import validate_blocks

_ID=re.compile(r'[a-zA-Z0-9_-]{4,50}\Z')

def editor_css(blocks,prefix=""):
    tablet=[];mobile=[]
    def walk(items):
        for b in items:
            uid=b['id']
            if not _ID.fullmatch(uid):continue
            s=b.get('style') or {}
            tp=s.get('tablet_padding',50);mp=s.get('mobile_padding',28)
            tp=max(0,min(120,int(tp)));mp=max(0,min(120,int(mp)))
            ident=prefix+f'.sf-section[data-block="{uid}"]'
            tablet.append(f'{ident}{{--sf-pad:{tp}px}}')
            mobile.append(f'{ident}{{--sf-pad:{mp}px}}')
            if s.get('hide_tablet') is True:tablet.append(f'{ident}{{display:none!important}}')
            if s.get('hide_mobile') is True:mobile.append(f'{ident}{{display:none!important}}')
            if b['type']=='layout':
                selector=prefix+f'.sf-layout-grid[data-layout="{uid}"]'
                tablet.append(f'{selector}{{grid-template-columns:repeat({b["tablet_columns"]},minmax(0,1fr))!important}}')
                mobile.append(f'{selector}{{grid-template-columns:repeat({b["mobile_columns"]},minmax(0,1fr))!important}}')
                for ci,col in enumerate(b['columns'],1):
                    target=selector+f'>.sf-layout-column[data-col="{ci}"]'
                    for dev,rules in [('tablet',tablet),('mobile',mobile)]:
                        rules.append(f'{target}{{order:{col[dev+"_order"]};grid-column:span {col[dev+"_span"]}}}')
                        if col['hide_'+dev]:rules.append(f'{target}{{display:none!important}}')
                    walk(col['blocks'])
    walk(validate_blocks(blocks))
    # Breakpoints are intentionally exclusive: phone has tablet rules plus
    # phone overrides. Phone controls are appended after tablet controls.
    return '@media(max-width:820px){'+''.join(tablet)+'}@media(max-width:540px){'+''.join(mobile)+'}'

def route_key(route):
    return hashlib.sha256(str(route).encode()).hexdigest()[:16]

def site_css(entries):
    styles=[]
    for entry in entries:
        try:meta=json.loads(entry.get('meta_json') or '{}')
        except (TypeError,ValueError):continue
        if isinstance(meta.get('blocks'),list) and meta['blocks']:
            styles.append(editor_css(meta['blocks'],prefix=f'body[data-siteforge-route="{route_key(entry.get("route","/"))}"] '))
    # Identical generated IDs may occur on different pages. Styles are scoped
    # to block IDs and remain deterministic; validate each page independently.
    return ''.join(styles)