import { findPythonVersionMatches, type VersionMatch } from '../scanning';

export interface RewriteContext {

filePath: string;

originalContent: string;

fromVersion: string;

toVersion: string;

}

export interface PatchResult {

filePath: string;

originalContent: string;

updatedContent: string;

changed: boolean;

replacements: VersionMatch[];

fromVersion: string;

toVersion: string;

}

function shareTrack(fromVersion: string, toVersion: string): boolean {

const fromParts = fromVersion.split('.');

const toParts = toVersion.split('.');

return fromParts[0] === toParts[0] && fromParts[1] === toParts[1];

}

export function computePatch(context: RewriteContext): PatchResult {

const { filePath, originalContent, fromVersion, toVersion } = context;

if (!shareTrack(fromVersion, toVersion)) {

return {

filePath,

originalContent,

updatedContent: originalContent,

changed: false,

replacements: [],

fromVersion,

toVersion,

};

}

const matches = findPythonVersionMatches(filePath, originalContent);

const replacements = matches.filter((match) => match.matched === fromVersion);

if (replacements.length === 0) {

return {

filePath,

originalContent,

updatedContent: originalContent,

changed: false,

replacements: [],

fromVersion,

toVersion,

};

}

const sortedReplacements = [...replacements].sort((a, b) => a.index - b.index);

let cursor = 0;

let updatedContent = '';

for (const replacement of sortedReplacements) {

const start = replacement.index;

const end = start + fromVersion.length;

updatedContent += originalContent.slice(cursor, start);

updatedContent += toVersion;

cursor = end;

}

updatedContent += originalContent.slice(cursor);

const changed = cursor !== 0 && updatedContent !== originalContent;

return {

filePath,

originalContent,

updatedContent,

changed,

replacements,

fromVersion,

toVersion,

};

}