package main

import (
	"context"
	"fmt"
	"log"
	"sort"
	"teafolio/gitea"
	"time"
)

// rearrangeOrder applies rearrangements from the OverrideOrder configuration.
func (this *Application) rearrangeOrder(repos []gitea.Repo) ([]gitea.Repo, error) {

	if len(this.cfg.OverrideOrder) == 0 {
		return repos, nil // nothing to do
	}

	// Collect pre-existing positions for repos
	reposByName := make(map[string]gitea.Repo, len(repos))
	for _, repo := range repos {
		reposByName[repo.Name] = repo
	}

	// Sort target insertion positions by lowest-first
	type insertionPosition struct {
		pos      int
		repoName string
	}
	insertAt := make([]insertionPosition, 0, len(this.cfg.OverrideOrder))

	for rn, rpos := range this.cfg.OverrideOrder {
		insertAt = append(insertAt, insertionPosition{len(repos) - rpos - 1, rn})
	}
	sort.Slice(insertAt, func(i, j int) bool {
		return insertAt[i].pos < insertAt[j].pos
	})

	// Walking-insertion loop
	ret := make([]gitea.Repo, 0, len(repos))
	nextRepo := 0
	nextOverride := 0
	for {
		if nextOverride < len(insertAt) && insertAt[nextOverride].pos == len(ret) {
			// We have an override to insert at this position
			ret = append(ret, reposByName[insertAt[nextOverride].repoName])
			nextOverride++

		} else if nextRepo < len(repos) {
			// There are still other repos to insert generally
			if _, ok := this.cfg.OverrideOrder[repos[nextRepo].Name]; ok {
				// This repo has an overridden position. Don't insert it generally here
				nextRepo++

			} else {
				// This repo does not have an overriden position. Here is fine
				ret = append(ret, repos[nextRepo])
				nextRepo++
			}

		} else {
			// There are no more overrides to insert and there are no remaining
			// non-override repos
			// That means we're done
			break
		}
	}

	if len(ret) != len(repos) {
		return nil, fmt.Errorf("Failed to apply OverrideOrder (got %d of %d repositories)", len(ret), len(repos))
	}

	return ret, nil
}

func (this *Application) sync(ctx context.Context) (bool, error) {

	// List repositories on Gitea
	repos, err := this.gitea.Repos(ctx)
	if err != nil {
		return false, err
	}

	// Compare this list of repositories to our existing one
	// If the repository is new, or if it's update-time has changed since we last
	// saw it, then re-refresh its real git commit timestamps
	// Otherwise copy them from the previous version

	this.reposMut.RLock() // readonly

	anyChanges := false
	if len(repos) != len(this.reposCache) {
		anyChanges = true
	}

	for i, rr := range repos {
		if idx, ok := this.reposAlphabeticalOrder[rr.Name]; ok && this.reposCache[idx].GiteaUpdated == rr.GiteaUpdated {
			// Already exists in cache with same Gitea update time
			// Copy timestamps
			repos[i] = this.reposCache[idx]

		} else {

			// New repo, or Gitea has updated timestamp
			anyChanges = true

			// Refresh timestamps
			err := this.gitea.PopulateCommitInfo(ctx, &rr)
			if err != nil {
				log.Printf("loading branches for '%s': %s", rr.Name, err)
				rr.NewestCommit = rr.GiteaUpdated // best guess
			}

			// Refresh topics
			err = this.gitea.PopulateTopics(ctx, &rr)
			if err != nil {
				log.Printf("loading topics for '%s': %s", rr.Name, err)
			}

			// Save
			repos[i] = rr
		}
	}

	this.reposMut.RUnlock()

	//
	if !anyChanges {
		return false, nil // nothing to do
	}

	// We have a final updated repos array

	// Sort repos once alphabetically, to get alphabetical indexes...
	sort.Slice(repos, func(i, j int) bool {
		return repos[i].Name < repos[j].Name
	})
	alphabeticalOrderIndexes := make(map[string]int, len(repos))
	for idx, repo := range repos {
		alphabeticalOrderIndexes[repo.Name] = idx
	}

	// But then make sure the final sort is by most-recently-created
	sort.Slice(repos, func(i, j int) bool {
		return repos[i].GiteaCreated.After(repos[j].GiteaCreated)
	})
	reordered, err := this.rearrangeOrder(repos)
	if err != nil {
		log.Printf("Reorder failure: %s", err.Error())
	} else {
		repos = reordered
	}

	// Commit our changes for the other threads to look at
	this.reposMut.Lock()
	this.reposCache = repos
	this.reposAlphabeticalOrder = alphabeticalOrderIndexes
	this.reposMut.Unlock()

	// Done
	return true, nil
}

func (this *Application) syncWorker(ctx context.Context) {

	t := time.NewTicker(30 * time.Minute)
	defer t.Stop()

	for {
		anyChanges, err := this.sync(ctx)
		if err != nil {
			// log and continue
			log.Printf("Refreshing repositories: %s", err.Error())
		}
		if anyChanges {
			log.Printf("Repositories updated")
		}

		select {
		case <-t.C:
			continue

		case <-ctx.Done():
			return
		}
	}
}