package com.vincent.rsf.server.ai.service.impl;

import com.vincent.rsf.server.ai.dto.AiPromptPreviewDto;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;

import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

@Component
public class AiPromptRenderSupport {

    private static final Pattern VARIABLE_PATTERN = Pattern.compile("\\{\\{?([a-zA-Z0-9_.-]+)}}?");

    public AiPromptPreviewDto render(String systemPrompt, String userPromptTemplate, String input, Map<String, Object> metadata) {
        String finalInput = input == null ? "" : input;
        return AiPromptPreviewDto.builder()
                .renderedSystemPrompt(renderTemplate(systemPrompt, finalInput, metadata))
                .renderedUserPrompt(renderUserPrompt(userPromptTemplate, finalInput, metadata))
                .resolvedVariables(resolveVariables(systemPrompt, userPromptTemplate, metadata))
                .build();
    }

    public String renderUserPrompt(String userPromptTemplate, String input, Map<String, Object> metadata) {
        if (!StringUtils.hasText(userPromptTemplate)) {
            return input;
        }
        String rendered = replaceTemplateVariables(userPromptTemplate, input, metadata);
        if (Objects.equals(rendered, userPromptTemplate)) {
            return userPromptTemplate + "\n\n" + input;
        }
        return rendered;
    }

    private String renderTemplate(String template, String input, Map<String, Object> metadata) {
        if (!StringUtils.hasText(template)) {
            return template;
        }
        return replaceTemplateVariables(template, input, metadata);
    }

    private String replaceTemplateVariables(String template, String input, Map<String, Object> metadata) {
        String rendered = template
                .replace("{{input}}", input)
                .replace("{input}", input);
        if (metadata == null || metadata.isEmpty()) {
            return rendered;
        }
        for (Map.Entry<String, Object> entry : metadata.entrySet()) {
            String value = entry.getValue() == null ? "" : String.valueOf(entry.getValue());
            rendered = rendered.replace("{{" + entry.getKey() + "}}", value);
            rendered = rendered.replace("{" + entry.getKey() + "}", value);
        }
        return rendered;
    }

    private List<String> resolveVariables(String systemPrompt, String userPromptTemplate, Map<String, Object> metadata) {
        LinkedHashSet<String> variables = new LinkedHashSet<>();
        collectVariables(variables, systemPrompt);
        collectVariables(variables, userPromptTemplate);
        if (metadata != null && !metadata.isEmpty()) {
            variables.addAll(metadata.keySet());
        }
        return new ArrayList<>(variables);
    }

    private void collectVariables(LinkedHashSet<String> variables, String template) {
        if (!StringUtils.hasText(template)) {
            return;
        }
        Matcher matcher = VARIABLE_PATTERN.matcher(template);
        while (matcher.find()) {
            variables.add(matcher.group(1));
        }
    }
}