"""Browser tasks with explicit semantic DOM and computed-style checks."""
from html import escape

HTML_BASES=[
 ('heading','h1','<h1>Welcome</h1>','an h1 heading reading Welcome',{}),
 ('paragraph','p','<p>Hello reader</p>','a paragraph reading Hello reader',{}),
 ('link','a','<a href="/help">Help</a>','a Help link to /help',{'href':'/help'}),
 ('button','button','<button type="button">Save</button>','a Save button with type button',{'type':'button'}),
 ('image','img','<img src="icon.png" alt="Star">','an image sourced from icon.png with alt text Star',{'src':'icon.png','alt':'Star'}),
 ('email','input','<input type="email" name="email">','an email input named email',{'type':'email','name':'email'}),
 ('checkbox','input','<input type="checkbox" name="agree">','a checkbox named agree',{'type':'checkbox','name':'agree'}),
 ('form','form','<form action="/send" method="post"><button>Send</button></form>','a POST form targeting /send containing a Send button',{'action':'/send','method':'post'}),
 ('list','ul','<ul><li>Tea</li><li>Water</li></ul>','an unordered list containing Tea then Water',{}),
 ('ordered_list','ol','<ol><li>Open</li><li>Close</li></ol>','an ordered list containing Open then Close',{}),
 ('navigation','nav','<nav><a href="/">Home</a></nav>','a navigation element with a Home link to /',{}),
 ('article','article','<article><h2>News</h2><p>Today</p></article>','an article with an h2 News and a paragraph Today',{}),
 ('footer','footer','<footer>Copyright</footer>','a footer reading Copyright',{}),
 ('quote','blockquote','<blockquote cite="/source">Be kind</blockquote>','a blockquote reading Be kind citing /source',{'cite':'/source'}),
 ('code','pre','<pre><code>x = 1</code></pre>','a preformatted code block reading x = 1',{}),
 ('details','details','<details><summary>More</summary><p>Details</p></details>','a details element with summary More and paragraph Details',{}),
 ('select','select','<select name="color"><option value="red">Red</option><option value="blue">Blue</option></select>','a select named color with Red/red and Blue/blue options',{'name':'color'}),
 ('textarea','textarea','<textarea name="note" rows="3">Note</textarea>','a textarea named note with three rows initially reading Note',{'name':'note','rows':'3'}),
 ('label','label','<label for="username">Name</label>','a Name label associated with input ID username',{'for':'username'}),
 ('progress','progress','<progress max="10" value="4">4/10</progress>','a progress element with maximum 10 and value 4',{'max':'10','value':'4'}),
]
GLOBAL=[('title','Information','a title attribute of Information'),('lang','en','English language via lang'),
 ('dir','rtl','right-to-left direction via dir'),('hidden','','the hidden attribute'),
 ('tabindex','0','keyboard focus via tabindex 0'),('contenteditable','true','contenteditable set to true')]

def html_assertions(markup,prefix=''):
    # Derive structural checks from the authored spec tree, not candidate text.
    from html.parser import HTMLParser
    class Parse(HTMLParser):
        def __init__(self):super().__init__();self.stack=[];self.counts={};self.out=[]
        def handle_starttag(self,tag,attrs):
            parent=self.stack[-1][0] if self.stack else prefix
            key=(parent,tag);self.counts[key]=self.counts.get(key,0)+1
            selector=(parent+' > ' if parent else '')+tag+f':nth-of-type({self.counts[key]})'
            self.out.append({'kind':'exists','selector':selector})
            for k,v in attrs:self.out.append({'kind':'attribute','selector':selector,'name':k,'value':v or ''})
            if tag not in ('img','input','br','hr','meta','link'):self.stack.append((selector,tag))
        def handle_endtag(self,tag):
            if self.stack and self.stack[-1][1]==tag:self.stack.pop()
        def handle_data(self,text):
            if text.strip() and self.stack:self.out.append({'kind':'text','selector':self.stack[-1][0],'value':text})
    p=Parse();p.feed(markup);return p.out

def html_tasks():
    tasks=[]
    for name,tag,code,desc,attrs in HTML_BASES:
        for attr,value,detail in GLOBAL:
            markup=code.replace('<'+tag,'<'+tag+' '+attr+'="'+value+'"',1)
            tasks.append(('easy',{'kind':'html','base':name,'feature':attr},'Create '+desc+'. On its outer element, set '+detail+'. Return an HTML fragment.',markup))
    for i,(name,tag,code,desc,attrs) in enumerate(HTML_BASES):
        for offset,wrapper in ((1,'section'),(4,'aside'),(9,'div')):
            _,_,code2,desc2,_=HTML_BASES[(i+offset)%len(HTML_BASES)]
            markup=f'<{wrapper}>{code}{code2}</{wrapper}>'
            tasks.append(('medium',{'kind':'html','pair':[i,(i+offset)%20],'wrapper':wrapper},f'Create a {wrapper} containing {desc}, followed by {desc2}. Return an HTML fragment.',markup))
    for i,(_,_,code,desc,_) in enumerate(HTML_BASES):
        _,_,code2,desc2,_=HTML_BASES[(i+7)%20]
        markup=f'<main><section>{code}</section><aside>{code2}</aside></main>'
        tasks.append(('moderate',{'kind':'html','layout':[i,(i+7)%20]},f'Create a main element. Put {desc} inside its section, and {desc2} inside its following aside. Return an HTML fragment.',markup))
    return [dict(difficulty=d,spec=s,prompt=p,reference=c,fixture='',checks=html_assertions(c)) for d,s,p,c in tasks]

# Fixed values are chosen to have exact, stable computed representations.
CSS_PROPERTIES=[
 ('color','rgb(10, 20, 30)'),('background-color','rgb(240, 220, 200)'),('font-size','20px'),('font-weight','700'),
 ('font-style','italic'),('text-align','center'),('text-transform','uppercase'),('letter-spacing','2px'),
 ('word-spacing','4px'),('line-height','28px'),('text-indent','12px'),('white-space','pre'),
 ('padding-top','8px'),('padding-right','10px'),('padding-bottom','12px'),('padding-left','14px'),
 ('margin-top','6px'),('margin-right','8px'),('margin-bottom','10px'),('margin-left','12px'),
 ('border-top-width','3px'),('border-bottom-color','rgb(0, 80, 120)'),('border-radius','6px'),('opacity','0.5'),
 ('width','120px'),('height','60px'),('min-width','90px'),('max-width','180px'),('box-sizing','border-box'),
 ('display','flex'),('flex-direction','column'),('justify-content','center'),('align-items','center'),('gap','8px'),
 ('position','relative'),('top','5px'),('overflow-x','hidden'),('visibility','hidden'),('cursor','pointer'),('list-style-type','square')]
BASE_CSS='* { box-sizing: content-box; } .target,.other { border: 1px solid black; width:200px; height:80px; min-width:0; max-width:none; margin:0; padding:0; display:block; position:static; }'
FIXTURE='<div id="scope"><div id="target" class="target" data-kind="card">Alpha<span>One</span><span>Two</span></div><div class="other">Beta</div></div><div class="target" id="outside">Outside</div>'

def css_tasks():
    tasks=[]
    for prop,val in CSS_PROPERTIES:
        for sel,description,affected in [('.target','every element with class target',['#target','#outside']),('#target','only the element with ID target',['#target']),('#scope > .target','only direct children of #scope having class target',['#target'])]:
            spec={'kind':'css','selector':sel,'declarations':{prop:val}}
            checks=[{'kind':'style','selector':x,'property':prop,'value':val} for x in affected]
            extra = 'display: flex;' if prop in ('flex-direction','justify-content','align-items','gap') else ('position: relative;' if prop=='top' else '')
            if extra:
                extra_prop='display' if prop!='top' else 'position'
                extra_val='flex' if prop!='top' else 'relative'
                checks += [{'kind':'style','selector':x,'property':extra_prop,'value':extra_val} for x in affected]
                spec['declarations'][extra_prop]=extra_val
            if prop=='flex-direction':checks += [{'kind':'layout_column','selector':x} for x in affected]
            if prop=='display':checks += [{'kind':'layout_row','selector':x} for x in affected]
            checks +=[{'kind':'unchanged','selector':'.other','property':prop}]
            if len(affected)==1:checks +=[{'kind':'unchanged','selector':'#outside','property':prop}]
            extra_instruction = ' Use flex display.' if extra.startswith('display') else (' Use relative positioning.' if extra else '')
            tasks.append(dict(difficulty='easy',spec=spec,prompt=f'Style {description}: set {prop} to {val}.{extra_instruction} Leave other elements unchanged. Return CSS only.',reference=f'{sel} {{ {prop}: {val}; {extra} }}',fixture=FIXTURE,checks=checks))
    pairs=[]
    # Avoid interactions that would invalidate literal computed values.
    for i in range(20):
        for offset in (4,7,11):pairs.append((i,(i+offset)%20))
    for i,j in pairs:
        p,v=CSS_PROPERTIES[i];q,w=CSS_PROPERTIES[j]
        spec={'kind':'css','selector':'#scope > .target','declarations':{p:v,q:w}}
        checks=[{'kind':'style','selector':'#target','property':k,'value':x} for k,x in ((p,v),(q,w))]
        checks +=[{'kind':'unchanged','selector':'.other','property':k} for k in (p,q)]
        tasks.append(dict(difficulty='medium',spec=spec,prompt=f'For direct children of #scope with class target, set {p} to {v} and {q} to {w}. Leave .other unchanged. Return CSS only.',reference=f'#scope > .target {{ {p}: {v}; {q}: {w}; }}',fixture=FIXTURE,checks=checks))
    for i,(prop,val) in enumerate(CSS_PROPERTIES[:20]):
        # Baseline captured before candidate CSS; test both sides of the breakpoint.
        spec={'kind':'css','selector':'#target','declarations':{prop:val},'max_width':600}
        checks=[{'kind':'style','selector':'#target','property':prop,'value':val,'viewport':480},
                {'kind':'unchanged','selector':'#target','property':prop,'viewport':900},
                {'kind':'unchanged','selector':'.other','property':prop,'viewport':480}]
        tasks.append(dict(difficulty='moderate',spec=spec,prompt=f'At viewport widths at most 600px, set {prop} to {val} on #target. At wider widths, preserve its original style. Never change .other. Return CSS only.',reference=f'@media (max-width: 600px) {{ #target {{ {prop}: {val}; }} }}',fixture=FIXTURE,checks=checks))
    return tasks

DOM_FIXTURE='<button id="action">Go</button><input id="input" value=""><p id="output">0</p><ul id="items"></ul><input id="check" type="checkbox">'
DOM_ACTIONS=[
 ('greeting','make #output read Hello',"o.textContent='Hello'",[{'kind':'text','selector':'#output','value':'Hello'}]),
 ('increment','increase the integer in #output by one',"o.textContent=String(Number(o.textContent)+1)",[{'kind':'text','selector':'#output','value':'2'}]),
 ('decrement','decrease the integer in #output by one',"o.textContent=String(Number(o.textContent)-1)",[{'kind':'text','selector':'#output','value':'-2'}]),
 ('mirror','copy the input value into #output',"o.textContent=i.value",[{'kind':'text','selector':'#output','value':'Ab 9'}]),
 ('uppercase','copy the uppercased input into #output',"o.textContent=i.value.toUpperCase()",[{'kind':'text','selector':'#output','value':'AB 9'}]),
 ('length','put the input character count in #output',"o.textContent=String(i.value.length)",[{'kind':'text','selector':'#output','value':'4'}]),
 ('clear_input','clear the input value',"i.value=''",[{'kind':'value','selector':'#input','value':''}]),
 ('disable_input','disable the input',"i.disabled=true",[{'kind':'property','selector':'#input','name':'disabled','value':True}]),
 ('hide_output','hide #output using its hidden property',"o.hidden=true",[{'kind':'property','selector':'#output','name':'hidden','value':True}]),
 ('toggle_class','toggle class active on #output',"o.classList.toggle('active')",[{'kind':'attribute','selector':'#output','name':'class','value':''}]),
 ('append_item','append a list item containing the input to #items',"const li=document.createElement('li'); li.textContent=i.value; document.querySelector('#items').appendChild(li)",[{'kind':'count','selector':'#items > li','value':2},{'kind':'text','selector':'#items > li:first-child','value':'Ab 9'}]),
 ('check','check the checkbox',"document.querySelector('#check').checked=true",[{'kind':'property','selector':'#check','name':'checked','value':True}]),
 ('title','set #output title to the input value',"o.title=i.value",[{'kind':'attribute','selector':'#output','name':'title','value':'Ab 9'}]),
 ('reverse','copy the reversed input into #output',"o.textContent=i.value.split('').reverse().join('')",[{'kind':'text','selector':'#output','value':'9 bA'}]),
 ('mark_empty','set #output to Empty if input is empty, otherwise Filled',"o.textContent=i.value.length ? 'Filled':'Empty'",[{'kind':'text','selector':'#output','value':'Filled'}]),
]

def dom_tasks():
    tasks=[]
    for name,desc,body,checks in DOM_ACTIONS:
        spec={'kind':'dom','event':'click','action':name}
        code="function setup() {\n  const i=document.querySelector('#input'), o=document.querySelector('#output');\n  document.querySelector('#action').addEventListener('click', () => { "+body+"; });\n}\n"
        tasks.append(dict(difficulty='medium',spec=spec,prompt=f'Implement setup(). When #action is clicked, {desc}. Attach an event listener; do not perform the action before a click.',reference=code,fixture=DOM_FIXTURE,checks=checks,steps=[{'action':'fill','selector':'#input','value':'Ab 9'},{'action':'click','selector':'#action'},{'action':'click','selector':'#action'}]))
    for name,desc,body,checks in DOM_ACTIONS[3:8]:
        code="function setup() {\n  const i=document.querySelector('#input'), o=document.querySelector('#output');\n  i.addEventListener('input', () => { "+body+"; });\n}\n"
        tasks.append(dict(difficulty='moderate',spec={'kind':'dom','event':'input','action':name},prompt=f'Implement setup(). On an input event from #input, {desc}. Use a listener, leave the initial page unchanged, and handle repeated events.',reference=code,fixture=DOM_FIXTURE,checks=checks,steps=[{'action':'set_value','selector':'#input','value':'Ab 9'},{'action':'event','selector':'#input','value':'input'}]))
    return tasks