app.py

import streamlit as st
import openai
import os
import re
import json

# ── Page config ────────────────────────────────────────────────────────────────
st.set_page_config(
    page_title="CodeShift · AI Code Converter",
    page_icon="⚡",
    layout="wide",
)

# ── Styling ────────────────────────────────────────────────────────────────────
st.markdown("""
<style>
@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;600&family=Syne:wght@700;800&display=swap');

html, body, [class*="css"] { font-family: 'Syne', sans-serif; }

.header {
    background: linear-gradient(135deg, #1a1040, #0d1a2a);
    padding: 24px 32px;
    border-radius: 12px;
    margin-bottom: 24px;
}
.header h1 {
    font-size: 2rem; font-weight: 800; margin: 0;
    background: linear-gradient(90deg, #7c6af7, #3ecfcf);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.header p { color: #7a7f94; margin: 4px 0 0; font-size: 0.9rem; }

.status-box { padding: 10px 16px; border-radius: 8px; font-size: 0.88rem; margin-top: 8px; }
.status-ok   { background: #0d2b1f; border-left: 3px solid #3ecf8e; color: #3ecf8e; }
.status-err  { background: #2b0d0d; border-left: 3px solid #f76464; color: #f76464; }
.status-info { background: #1a1a2e; border-left: 3px solid #7c6af7; color: #a99ff7; }

textarea { font-family: 'JetBrains Mono', monospace !important; font-size: 0.82rem !important; }
</style>
""", unsafe_allow_html=True)

# ── OpenAI client ──────────────────────────────────────────────────────────────
client = openai.OpenAI(api_key=os.environ.get("OPENAI_API_KEY"))

LANGUAGES = [
    "Python", "JavaScript", "TypeScript", "Java", "C", "C++", "C#",
    "Go", "Rust", "Ruby", "PHP", "Swift", "Kotlin", "Bash/Shell", "SQL",
]

# ── AI helpers ─────────────────────────────────────────────────────────────────

def validate_language(code: str, selected: str):
    resp = client.chat.completions.create(
        model="gpt-4o", temperature=0,
        messages=[
            {"role": "system", "content": 'Detect the programming language. Reply ONLY with JSON: {"language":"X","confidence":"high/medium/low","reason":"..."}'},
            {"role": "user",   "content": code[:3000]},
        ],
    )
    raw  = re.sub(r"```[a-z]*\n?|```", "", resp.choices[0].message.content).strip()
    data = json.loads(raw)
    detected = data.get("language", "Unknown")
    match    = detected.lower() == selected.lower()
    return detected, data.get("confidence", "?"), data.get("reason", ""), match


def convert_code(code: str, src: str, tgt: str, notes: str):
    prompt = (
        f"Convert the {src} code to idiomatic {tgt}. "
        f"Preserve all logic. Add comments for non-obvious parts. "
        f"Return ONLY raw code — no markdown fences, no preamble."
        + (f" Style notes: {notes}" if notes.strip() else "")
    )
    resp = client.chat.completions.create(
        model="gpt-4o", temperature=0.2,
        messages=[
            {"role": "system", "content": prompt},
            {"role": "user",   "content": code},
        ],
    )
    return re.sub(r"```[a-z]*\n?|```", "", resp.choices[0].message.content).strip()


def explain_code(code: str, lang: str):
    resp = client.chat.completions.create(
        model="gpt-4o", temperature=0.3,
        messages=[
            {"role": "system", "content": "Explain this code clearly in plain English using bullet points. Be concise."},
            {"role": "user",   "content": f"{lang} code:\n\n{code[:4000]}"},
        ],
    )
    return resp.choices[0].message.content.strip()

# ── Header ─────────────────────────────────────────────────────────────────────
st.markdown("""
<div class="header">
  <h1>⚡ CodeShift</h1>
  <p>AI-powered code converter &amp; analyser · GPT-4o</p>
</div>
""", unsafe_allow_html=True)

# ── Tabs ───────────────────────────────────────────────────────────────────────
tab1, tab2, tab3 = st.tabs(["🔄 Convert", "💡 Explain", "🔎 Detect"])

# ════════════════════════
# TAB 1 — CONVERT
# ════════════════════════
with tab1:
    col_l, col_r = st.columns(2, gap="medium")

    with col_l:
        st.markdown("### Source Code")
        src_lang    = st.selectbox("Source Language", LANGUAGES, index=0, key="src_lang")
        src_code    = st.text_area("", height=380, placeholder="# Paste your source code here…", key="src_code")
        style_notes = st.text_input("Style notes (optional)", placeholder="e.g. 'use async/await', 'add type hints'…")

        c1, c2, c3 = st.columns(3)
        validate_btn = c1.button("🔍 Validate",  use_container_width=True)
        convert_btn  = c2.button("⚡ Convert",   use_container_width=True, type="primary")
        clear_btn    = c3.button("🗑 Clear",      use_container_width=True)

        if validate_btn:
            if not src_code.strip():
                st.markdown('<div class="status-box status-info">⚪ Paste some code first.</div>', unsafe_allow_html=True)
            else:
                with st.spinner("Detecting language…"):
                    detected, conf, reason, match = validate_language(src_code, src_lang)
                if match:
                    st.markdown(f'<div class="status-box status-ok">✅ Detected <b>{detected}</b> — matches your selection! (Confidence: {conf})<br><small>{reason}</small></div>', unsafe_allow_html=True)
                else:
                    st.markdown(f'<div class="status-box status-err">❌ Detected <b>{detected}</b> but you selected <b>{src_lang}</b> (Confidence: {conf})<br><small>{reason}</small></div>', unsafe_allow_html=True)

        if clear_btn:
            st.session_state["src_code"] = ""
            st.session_state["converted"] = ""
            st.rerun()

    with col_r:
        st.markdown("### Converted Code")
        tgt_lang = st.selectbox("Target Language", LANGUAGES, index=1, key="tgt_lang")

        if convert_btn:
            if not src_code.strip():
                st.warning("Paste some source code first.")
            elif src_lang == tgt_lang:
                st.info("Source and target languages are the same.")
            else:
                with st.spinner(f"Converting {src_lang} → {tgt_lang}…"):
                    result = convert_code(src_code, src_lang, tgt_lang, style_notes)
                st.session_state["converted"]  = result
                st.session_state["conv_langs"] = (src_lang, tgt_lang)

        converted = st.session_state.get("converted", "")
        langs     = st.session_state.get("conv_langs", ("", ""))

        if converted:
            st.success(f"✅ Converted {langs[0]} → {langs[1]}")

        st.text_area("", value=converted, height=380,
                     placeholder="# Converted code appears here…",
                     key="tgt_code")

# ════════════════════════
# TAB 2 — EXPLAIN
# ════════════════════════
with tab2:
    col_l, col_r = st.columns(2, gap="medium")

    with col_l:
        st.markdown("### Paste Code to Explain")
        exp_lang = st.selectbox("Language", LANGUAGES, key="exp_lang")
        exp_code = st.text_area("", height=380, placeholder="# Paste code here…", key="exp_code")
        exp_btn  = st.button("💡 Explain", type="primary", use_container_width=True)

    with col_r:
        st.markdown("### AI Explanation")
        if exp_btn:
            if not exp_code.strip():
                st.warning("Paste some code first.")
            else:
                with st.spinner("Explaining…"):
                    st.session_state["explanation"] = explain_code(exp_code, exp_lang)

        if st.session_state.get("explanation"):
            st.markdown(st.session_state["explanation"])
        else:
            st.caption("Explanation will appear here after you click Explain.")

# ════════════════════════
# TAB 3 — DETECT
# ════════════════════════
with tab3:
    col_l, col_r = st.columns(2, gap="medium")

    with col_l:
        st.markdown("### Mystery Code")
        det_code = st.text_area("", height=380, placeholder="# Paste any code here…", key="det_code")
        det_btn  = st.button("🔎 Detect Language", type="primary", use_container_width=True)

    with col_r:
        st.markdown("### Detection Result")
        if det_btn:
            if not det_code.strip():
                st.warning("Paste some code first.")
            else:
                with st.spinner("Analysing…"):
                    detected, conf, reason, _ = validate_language(det_code, "")
                st.metric("Detected Language", detected)
                st.metric("Confidence", conf.capitalize())
                st.info(reason)
        else:
            st.caption("Results will appear here after detection.")

st.markdown("---")
st.markdown("<center style='color:#4a5068;font-size:0.78rem'>CodeShift · GPT-4o · Built with Streamlit</center>", unsafe_allow_html=True)