package service

import (
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"strings"
	"unicode/utf8"
)

const (
	maxAdapterRegexLen = 512
	maxAdapterSources  = 20
)

// TimelineGitAdapter 声明式提交导入配置（内置，不可在站点设置中编辑）
type TimelineGitAdapter struct {
	MaxPages   int                    `json:"max_pages"`
	MaxCommits int                    `json:"max_commits"`
	Sources    []TimelineGitSourceCfg `json:"sources"`
}

// TimelineGitSourceCfg 单个 Git 源
type TimelineGitSourceCfg struct {
	ID         string             `json:"id"`
	Host       string             `json:"host"` // 精确主机或 "*"
	ListPath   string             `json:"list_path"`
	CommitPath string             `json:"commit_path,omitempty"` // 单条 commit 页
	APIURL     string             `json:"api_url"`
	CommitAPI  string             `json:"commit_api,omitempty"`
	Query      map[string]string  `json:"query"`
	Headers    map[string]string  `json:"headers"`
	Pagination string             `json:"pagination"` // link_header | query_page
	Item       TimelineGitItemMap `json:"item"`
}

// TimelineGitItemMap JSON 点路径映射
type TimelineGitItemMap struct {
	SHA       string `json:"sha"`
	Date      string `json:"date"`
	Message   string `json:"message"`
	SourceURL string `json:"source_url"`
}

var allowedAdapterHeaders = map[string]bool{
	"user-agent":      true,
	"accept":          true,
	"accept-language": true,
}

// DefaultTimelineGitAdapterJSON 内置 GitHub + Gitea 模板
func DefaultTimelineGitAdapterJSON() string {
	return `{
  "max_pages": 10,
  "max_commits": 100,
  "sources": [
    {
      "id": "github",
      "host": "github.com",
      "list_path": "^/(?P<owner>[^/]+)/(?P<repo>[^/]+)/commits/(?P<ref>[^/]+)/?$",
      "commit_path": "^/(?P<owner>[^/]+)/(?P<repo>[^/]+)/commit/(?P<sha>[0-9a-fA-F]{7,64})/?$",
      "api_url": "https://api.github.com/repos/{owner}/{repo}/commits",
      "commit_api": "https://api.github.com/repos/{owner}/{repo}/commits/{sha}",
      "query": { "sha": "{ref}", "per_page": "100", "page": "{page}" },
      "headers": { "User-Agent": "jiang13-bbs", "Accept": "application/vnd.github+json" },
      "pagination": "link_header",
      "item": {
        "sha": "sha",
        "date": "commit.committer.date",
        "message": "commit.message",
        "source_url": "html_url"
      }
    },
    {
      "id": "gitea",
      "host": "*",
      "list_path": "^/(?P<owner>[^/]+)/(?P<repo>[^/]+)/commits/branch/(?P<ref>.+)/?$",
      "commit_path": "^/(?P<owner>[^/]+)/(?P<repo>[^/]+)/commit/(?P<sha>[0-9a-fA-F]{7,64})/?$",
      "api_url": "https://{host}/api/v1/repos/{owner}/{repo}/commits",
      "commit_api": "https://{host}/api/v1/repos/{owner}/{repo}/git/commits/{sha}",
      "query": { "sha": "{ref}", "limit": "50", "page": "{page}" },
      "headers": { "User-Agent": "jiang13-bbs", "Accept": "application/json" },
      "pagination": "query_page",
      "item": {
        "sha": "sha",
        "date": "created",
        "message": "commit.message",
        "source_url": "html_url"
      }
    }
  ]
}`
}

func validateTimelineGitAdapter(cfg *TimelineGitAdapter) error {
	if cfg.MaxPages < 1 || cfg.MaxPages > 50 {
		return errors.New("max_pages 须在 1–50")
	}
	if cfg.MaxCommits < 1 || cfg.MaxCommits > 500 {
		return errors.New("max_commits 须在 1–500")
	}
	if len(cfg.Sources) == 0 {
		return errors.New("至少配置一个 source")
	}
	if len(cfg.Sources) > maxAdapterSources {
		return errors.New("sources 过多")
	}
	seen := map[string]bool{}
	for i := range cfg.Sources {
		src := &cfg.Sources[i]
		src.ID = strings.TrimSpace(src.ID)
		if src.ID == "" {
			return fmt.Errorf("sources[%d].id 不能为空", i)
		}
		if seen[src.ID] {
			return fmt.Errorf("重复的 source id: %s", src.ID)
		}
		seen[src.ID] = true
		src.Host = strings.ToLower(strings.TrimSpace(src.Host))
		if src.Host == "" {
			return fmt.Errorf("%s.host 不能为空", src.ID)
		}
		if utf8.RuneCountInString(src.ListPath) > maxAdapterRegexLen {
			return fmt.Errorf("%s.list_path 过长", src.ID)
		}
		if _, err := regexp.Compile(src.ListPath); err != nil {
			return fmt.Errorf("%s.list_path 正则无效: %w", src.ID, err)
		}
		if src.CommitPath != "" {
			if _, err := regexp.Compile(src.CommitPath); err != nil {
				return fmt.Errorf("%s.commit_path 正则无效: %w", src.ID, err)
			}
		}
		if strings.TrimSpace(src.APIURL) == "" {
			return fmt.Errorf("%s.api_url 不能为空", src.ID)
		}
		if src.Pagination != "link_header" && src.Pagination != "query_page" {
			return fmt.Errorf("%s.pagination 须为 link_header 或 query_page", src.ID)
		}
		for k := range src.Headers {
			if !allowedAdapterHeaders[strings.ToLower(k)] {
				return fmt.Errorf("%s.headers 不允许字段 %s", src.ID, k)
			}
		}
		if src.Item.SHA == "" || src.Item.Date == "" || src.Item.Message == "" || src.Item.SourceURL == "" {
			return fmt.Errorf("%s.item 须包含 sha/date/message/source_url", src.ID)
		}
	}
	return nil
}

func (s *SettingService) loadTimelineGitAdapter() (*TimelineGitAdapter, error) {
	raw := DefaultTimelineGitAdapterJSON()
	var cfg TimelineGitAdapter
	if err := json.Unmarshal([]byte(raw), &cfg); err != nil {
		return nil, errors.New("内置提交导入规则无效")
	}
	if err := validateTimelineGitAdapter(&cfg); err != nil {
		return nil, errors.New("内置提交导入规则无效")
	}
	return &cfg, nil
}