import type { ScopeTextTemplateDiffLine } from '../types';

const buildLcsTable = (a: string[], b: string[]) => {
    const table = Array.from({ length: a.length + 1 }, () => Array(b.length + 1).fill(0));

    for (let i = a.length - 1; i >= 0; i--) {
        for (let j = b.length - 1; j >= 0; j--) {
            if (a[i] === b[j]) {
                table[i][j] = table[i + 1][j + 1] + 1;
            } else {
                table[i][j] = Math.max(table[i + 1][j], table[i][j + 1]);
            }
        }
    }

    return table;
};

export const createScopeTextDiff = (previousContent: string, nextContent: string): ScopeTextTemplateDiffLine[] => {
    const previousLines = previousContent.split('\n');
    const nextLines = nextContent.split('\n');
    const table = buildLcsTable(previousLines, nextLines);
    const diff: ScopeTextTemplateDiffLine[] = [];

    let i = 0;
    let j = 0;

    while (i < previousLines.length && j < nextLines.length) {
        if (previousLines[i] === nextLines[j]) {
            diff.push({ op: 'equal', text: previousLines[i] });
            i++;
            j++;
            continue;
        }

        if (table[i + 1][j] >= table[i][j + 1]) {
            diff.push({ op: 'remove', text: previousLines[i] });
            i++;
        } else {
            diff.push({ op: 'add', text: nextLines[j] });
            j++;
        }
    }

    while (i < previousLines.length) {
        diff.push({ op: 'remove', text: previousLines[i] });
        i++;
    }

    while (j < nextLines.length) {
        diff.push({ op: 'add', text: nextLines[j] });
        j++;
    }

    return diff;
};