package com.mydreamjob.skill;

import com.mydreamjob.skill.domain.SkillCategory;
import com.mydreamjob.skill.dto.SkillCloudItem;
import com.mydreamjob.skill.dto.SkillLearningPathItem;
import com.mydreamjob.skill.dto.SkillLearningPathResponse;
import com.mydreamjob.skill.dto.SkillMatchResponse;
import com.mydreamjob.skill.repository.SkillCategoryRepository;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;
import java.util.Locale;
import java.util.stream.IntStream;

@Service
@Transactional(readOnly = true)
public class SkillLearningPathService {

    private final SkillMatchService skillMatchService;
    private final SkillCategoryRepository skillCategoryRepository;

    public SkillLearningPathService(SkillMatchService skillMatchService,
                                    SkillCategoryRepository skillCategoryRepository) {
        this.skillMatchService = skillMatchService;
        this.skillCategoryRepository = skillCategoryRepository;
    }

    public SkillLearningPathResponse generate(Long studentUserId,
                                              Long industryId,
                                              Long occupationId,
                                              Long categoryId) {
        SkillMatchResponse matchResponse = skillMatchService.match(
                studentUserId, industryId, occupationId, categoryId);
        List<SkillCloudItem> missingSkills = matchResponse.missingSkills();
        List<SkillLearningPathItem> items = IntStream.range(0, missingSkills.size())
                .mapToObj(index -> toItem(missingSkills.get(index), index + 1, occupationId))
                .toList();

        return new SkillLearningPathResponse(items.size(), items);
    }

    private SkillLearningPathItem toItem(SkillCloudItem skill, int priority, Long occupationId) {
        SuggestionTemplate template = resolveTemplate(skill, occupationId);
        String skillName = skill.nameZh();
        return new SkillLearningPathItem(
                priority,
                skill.skillId(),
                skillName,
                skill.categoryId(),
                skill.categoryName(),
                template.render(skillName)
        );
    }

    private SuggestionTemplate resolveTemplate(SkillCloudItem skill, Long occupationId) {
        if (skill.categoryId() == null) {
            return SuggestionTemplate.GENERAL;
        }

        String templateCode = skillCategoryRepository
                .findByIdAndOccupationId(skill.categoryId(), occupationId)
                .map(SkillCategory::getSuggestionTemplateCode)
                .orElse(null);
        return SuggestionTemplate.fromCode(templateCode);
    }

    private enum SuggestionTemplate {
        PROGRAMMING_LANGUAGE("先掌握{skill}的基础语法和常见数据结构，再完成至少一个编码练习。"),
        FRAMEWORK("先理解{skill}的核心概念与生命周期，再通过一个小型项目练习集成。"),
        TOOL("先完成{skill}的安装与基础配置，再结合现有工程完成一次实际操作。"),
        GENERAL("先了解{skill}的核心概念和常见应用场景，再通过一个简短实践巩固。");

        private final String template;

        SuggestionTemplate(String template) {
            this.template = template;
        }

        String render(String skillName) {
            return template.replace("{skill}", skillName);
        }

        static SuggestionTemplate fromCode(String code) {
            if (code == null || code.isBlank()) {
                return GENERAL;
            }
            try {
                return valueOf(code.trim().toUpperCase(Locale.ROOT));
            } catch (IllegalArgumentException exception) {
                return GENERAL;
            }
        }
    }
}