package server

import (
	"context"
	"log/slog"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"git.wntrmute.dev/mc/mcdoc/internal/cache"
	"git.wntrmute.dev/mc/mcdoc/internal/gitea"
	"git.wntrmute.dev/mc/mcdoc/internal/render"
)

// Fetcher coordinates fetching content from Gitea and populating the cache.
type Fetcher struct {
	client       *gitea.Client
	renderer     *render.Renderer
	excludePaths []string
	excludeRepos map[string]bool
	concurrency  int
	log          *slog.Logger
}

// FetcherConfig holds fetcher configuration.
type FetcherConfig struct {
	Client       *gitea.Client
	Renderer     *render.Renderer
	ExcludePaths []string
	ExcludeRepos []string
	Concurrency  int
	Log          *slog.Logger
}

// NewFetcher creates a Fetcher.
func NewFetcher(cfg FetcherConfig) *Fetcher {
	excludeRepos := make(map[string]bool, len(cfg.ExcludeRepos))
	for _, name := range cfg.ExcludeRepos {
		excludeRepos[name] = true
	}

	if cfg.Concurrency < 1 {
		cfg.Concurrency = 4
	}
	if cfg.Log == nil {
		cfg.Log = slog.Default()
	}

	return &Fetcher{
		client:       cfg.Client,
		renderer:     cfg.Renderer,
		excludePaths: cfg.ExcludePaths,
		excludeRepos: excludeRepos,
		concurrency:  cfg.Concurrency,
		log:          cfg.Log,
	}
}

// FetchRepo fetches and renders all markdown files for a single repo.
func (f *Fetcher) FetchRepo(ctx context.Context, repo gitea.Repo) (*cache.RepoInfo, error) {
	files, err := f.client.ListMarkdownFiles(ctx, repo.Name, repo.DefaultBranch)
	if err != nil {
		return nil, err
	}

	sha, commitDate, err := f.client.LatestCommitSHA(ctx, repo.Name, repo.DefaultBranch)
	if err != nil {
		f.log.Warn("could not get latest commit", "repo", repo.Name, "error", err)
	}

	var docs []*cache.Document
	for _, filePath := range files {
		if f.isExcluded(filePath) {
			continue
		}

		content, err := f.client.FetchFileContent(ctx, repo.Name, repo.DefaultBranch, filePath)
		if err != nil {
			f.log.Warn("skip file", "repo", repo.Name, "file", filePath, "error", err)
			continue
		}

		result, err := f.renderer.Render(content)
		if err != nil {
			f.log.Warn("render failed", "repo", repo.Name, "file", filePath, "error", err)
			continue
		}

		urlPath := strings.TrimSuffix(filePath, filepath.Ext(filePath))
		title := titleFromHeadings(result.Headings)
		if title == "" {
			title = titleFromPath(filePath)
		}

		docs = append(docs, &cache.Document{
			Repo:        repo.Name,
			FilePath:    filePath,
			URLPath:     urlPath,
			Title:       title,
			HTML:        result.HTML,
			Headings:    result.Headings,
			LastUpdated: commitDate,
		})
	}

	return &cache.RepoInfo{
		Name:        repo.Name,
		Description: repo.Description,
		Docs:        docs,
		CommitSHA:   sha,
		FetchedAt:   time.Now(),
	}, nil
}

func (f *Fetcher) isExcluded(filePath string) bool {
	for _, pattern := range f.excludePaths {
		if strings.Contains(filePath, pattern) {
			return true
		}
	}
	return false
}

func titleFromHeadings(headings []render.Heading) string {
	for _, h := range headings {
		if h.Level == 1 {
			return h.Text
		}
	}
	if len(headings) > 0 {
		return headings[0].Text
	}
	return ""
}

func titleFromPath(filePath string) string {
	base := filepath.Base(filePath)
	return strings.TrimSuffix(base, filepath.Ext(base))
}

func fetchAllRepos(ctx context.Context, cfg BackgroundConfig) error {
	repos, err := cfg.Fetcher.client.ListRepos(ctx)
	if err != nil {
		return err
	}

	sem := make(chan struct{}, cfg.Fetcher.concurrency)
	var wg sync.WaitGroup
	var mu sync.Mutex
	var firstErr error

	for _, repo := range repos {
		if cfg.Fetcher.excludeRepos[repo.Name] {
			continue
		}

		wg.Add(1)
		go func(r gitea.Repo) {
			defer wg.Done()
			sem <- struct{}{}
			defer func() { <-sem }()

			info, err := cfg.Fetcher.FetchRepo(ctx, r)
			if err != nil {
				cfg.Log.Warn("fetch repo failed", "repo", r.Name, "error", err)
				mu.Lock()
				if firstErr == nil {
					firstErr = err
				}
				mu.Unlock()
				return
			}

			if len(info.Docs) > 0 {
				cfg.Cache.SetRepo(info)
			}
			cfg.Log.Info("fetched repo", "repo", r.Name, "docs", len(info.Docs))
		}(repo)
	}

	wg.Wait()
	return nil
}

func pollForChanges(ctx context.Context, cfg BackgroundConfig) error {
	repos, err := cfg.Fetcher.client.ListRepos(ctx)
	if err != nil {
		return err
	}

	for _, repo := range repos {
		if cfg.Fetcher.excludeRepos[repo.Name] {
			continue
		}

		sha, _, err := cfg.Fetcher.client.LatestCommitSHA(ctx, repo.Name, repo.DefaultBranch)
		if err != nil {
			cfg.Log.Warn("poll: could not check commit", "repo", repo.Name, "error", err)
			continue
		}

		cached := cfg.Cache.GetCommitSHA(repo.Name)
		if sha == cached {
			continue
		}

		cfg.Log.Info("repo changed, re-fetching", "repo", repo.Name, "old_sha", cached, "new_sha", sha)
		info, err := cfg.Fetcher.FetchRepo(ctx, repo)
		if err != nil {
			cfg.Log.Warn("poll: re-fetch failed", "repo", repo.Name, "error", err)
			continue
		}
		cfg.Cache.SetRepo(info)
	}

	return nil
}