import type { CodeFinding } from '../index.js';

const MAX_SNIPPET_CHARS = 500;
const MAX_PROMPT_CHARS = 30_000;

export const VERIFIER_SYSTEM_PROMPT = `You are a senior security engineer performing false-positive analysis on automated security scan findings.

Your task is to classify each finding as likely false positive or real vulnerability.

False-positive rules:
- Findings in files named *.example, *.sample, *.template, or under test/ directories are likely false positives.
- Placeholder values such as "your_key_here", "CHANGE_ME", "xxx" indicate false positives.
- Clearly public/example/demo values indicate false positives.
- YAML/JSON style or formatting issues (including wrong indentation) are always false positives.
- Auto-generated files like package-lock.json and *.min.js are likely false positives.

Return ONLY a valid JSON array.
No markdown.
No code fences.
No text outside the JSON array.`;

/**
 * Builds the user prompt for a verifier batch of code findings.
 */
export function buildVerificationPrompt(findings: CodeFinding[]): string {
	let findingsForPrompt = [...findings];
	let prompt = renderPrompt(findingsForPrompt, findings.length);

	while (prompt.length > MAX_PROMPT_CHARS && findingsForPrompt.length > 1) {
		findingsForPrompt = findingsForPrompt.slice(1);
		prompt = renderPrompt(findingsForPrompt, findings.length);
	}

	if (prompt.length > MAX_PROMPT_CHARS) {
		return prompt.slice(0, MAX_PROMPT_CHARS);
	}

	return prompt;
}

function renderPrompt(findings: CodeFinding[], originalCount: number): string {
	const droppedCount = originalCount - findings.length;
	const truncationNote = droppedCount > 0
		? ` ${droppedCount} oldest findings omitted due to prompt size limits.`
		: '';
	const header = `Analyze these ${findings.length} security findings and determine if each is real or FP.${truncationNote}`;

	const body = findings
		.map((finding, index) => {
			const rawSnippet = finding.snippet ?? '(no snippet available)';
			const snippet = truncateTextMiddle(rawSnippet, MAX_SNIPPET_CHARS, '\n...[SNIPPET TRUNCATED]...\n');
			const cwe = finding.cwe ?? 'null';
			const line = finding.line === null ? 'null' : String(finding.line);

			return [
				`=== FINDING ${index + 1} ===`,
				`Scanner: ${finding.scanner}`,
				`File: ${finding.file}`,
				`Line: ${line}`,
				`Severity: ${finding.severity}`,
				`Issue: ${finding.issue}`,
				`CWE: ${cwe}`,
				'',
				'Code snippet:',
				snippet,
				'==================',
			].join('\n');
		})
		.join('\n\n');

	const schema = [
		`Respond with JSON array of ${findings.length} objects:`,
		'[',
		'  {',
		'    "finding_index": 0,',
		'    "is_likely_fp": false,',
		'    "confidence": 97,',
		'    "reason": "one line reason",',
		'    "explanation": "detailed explanation why this is real or FP"',
		'  }',
		']',
	].join('\n');

	return `${header}\n\n${body}\n\n${schema}`;
}

function truncateTextMiddle(value: string, maxChars: number, marker: string): string {
	if (value.length <= maxChars) {
		return value;
	}

	if (maxChars <= marker.length + 2) {
		return value.slice(0, maxChars);
	}

	const budget = maxChars - marker.length;
	const startLength = Math.ceil(budget / 2);
	const endLength = Math.floor(budget / 2);
	return `${value.slice(0, startLength)}${marker}${value.slice(value.length - endLength)}`;
}