{% extends "base.html" %}
{% block title %}Text Diff - EveryTools{% endblock %}
{% block top_title %}Text Diff{% endblock %}

{% block content %}
<div class="client-tool">
    <div class="tool-header">
        <h1>Text Diff</h1>
        <p>Compare two texts and see the differences</p>
    </div>
    <div class="split-pane">
        <div class="pane">
            <div class="pane-header"><span>Original</span></div>
            <div class="pane-body">
                <textarea id="diff-left" placeholder="Paste original text..."></textarea>
            </div>
        </div>
        <div class="pane">
            <div class="pane-header"><span>Modified</span></div>
            <div class="pane-body">
                <textarea id="diff-right" placeholder="Paste modified text..."></textarea>
            </div>
        </div>
    </div>
    <button class="btn btn-primary" style="margin-top:1rem" onclick="computeDiff()">Compare</button>
    <div id="diff-output" style="margin-top:1rem"></div>
</div>
{% endblock %}

{% block scripts %}
<style>
.diff-view { font-family: "Consolas","Monaco",monospace; font-size: .85rem; border: 1px solid var(--border); border-radius: var(--radius); overflow: auto; max-height: 500px; }
.diff-line { padding: .15rem .6rem; white-space: pre-wrap; word-break: break-word; display: flex; }
.diff-num { color: var(--text-light); min-width: 3rem; text-align: right; padding-right: .6rem; user-select: none; flex-shrink: 0; }
.diff-add { background: #d4edda; }
.diff-del { background: #f8d7da; }
.diff-ctx { background: var(--surface); }
.diff-hdr { background: var(--bg); color: var(--text-light); font-weight: 600; padding: .3rem .6rem; }
.diff-stats { font-size: .85rem; margin-bottom: .5rem; }
.diff-stats .add { color: #28a745; font-weight: 600; }
.diff-stats .del { color: var(--danger); font-weight: 600; }
[data-theme="dark"] .diff-add { background: #0d2e14; }
[data-theme="dark"] .diff-del { background: #2e0d0d; }
[data-theme="dark"] .diff-stats .add { color: #4ecdc4; }
</style>
<script>
function computeDiff() {
    const a = document.getElementById("diff-left").value.split("\n");
    const b = document.getElementById("diff-right").value.split("\n");

    // Simple LCS-based diff
    const lcs = buildLCS(a, b);
    const lines = [];
    let i = 0, j = 0, li = 0;
    let adds = 0, dels = 0;

    while (li < lcs.length || i < a.length || j < b.length) {
        if (li < lcs.length) {
            // Output removals before next common line
            while (i < lcs[li][0]) { lines.push({type:"del", num: i+1, text: a[i]}); dels++; i++; }
            while (j < lcs[li][1]) { lines.push({type:"add", num: j+1, text: b[j]}); adds++; j++; }
            lines.push({type:"ctx", num: i+1, text: a[i]});
            i++; j++; li++;
        } else {
            while (i < a.length) { lines.push({type:"del", num: i+1, text: a[i]}); dels++; i++; }
            while (j < b.length) { lines.push({type:"add", num: j+1, text: b[j]}); adds++; j++; }
        }
    }

    const out = document.getElementById("diff-output");
    let html = `<div class="diff-stats"><span class="add">+${adds} additions</span> &nbsp; <span class="del">-${dels} deletions</span></div>`;
    html += '<div class="diff-view">';
    for (const l of lines) {
        const prefix = l.type === "add" ? "+" : l.type === "del" ? "-" : " ";
        const cls = l.type === "add" ? "diff-add" : l.type === "del" ? "diff-del" : "diff-ctx";
        const escaped = l.text.replace(/&/g,"&amp;").replace(/</g,"&lt;").replace(/>/g,"&gt;");
        html += `<div class="diff-line ${cls}"><span class="diff-num">${l.num}</span>${prefix} ${escaped}</div>`;
    }
    html += '</div>';
    if (adds === 0 && dels === 0) html = '<div style="color:var(--success);font-weight:500"><i class="bi bi-check-circle"></i> Texts are identical.</div>';
    out.innerHTML = html;
}

function buildLCS(a, b) {
    const m = a.length, n = b.length;
    const dp = Array.from({length: m+1}, () => new Array(n+1).fill(0));
    for (let i = 1; i <= m; i++)
        for (let j = 1; j <= n; j++)
            dp[i][j] = a[i-1] === b[j-1] ? dp[i-1][j-1]+1 : Math.max(dp[i-1][j], dp[i][j-1]);

    const result = [];
    let i = m, j = n;
    while (i > 0 && j > 0) {
        if (a[i-1] === b[j-1]) { result.unshift([i-1, j-1]); i--; j--; }
        else if (dp[i-1][j] > dp[i][j-1]) i--;
        else j--;
    }
    return result;
}
</script>
{% endblock %}