// Copyright 2020 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package repo

import (
	"context"
	"math"
	"sort"
	"strings"

	"code.gitea.io/gitea/models/db"
	"code.gitea.io/gitea/modules/timeutil"

	"github.com/go-enry/go-enry/v2"
)

// LanguageStat describes language statistics of a repository
type LanguageStat struct {
	ID          int64 `xorm:"pk autoincr"`
	RepoID      int64 `xorm:"UNIQUE(s) INDEX NOT NULL"`
	CommitID    string
	IsPrimary   bool
	Language    string             `xorm:"VARCHAR(50) UNIQUE(s) INDEX NOT NULL"`
	Percentage  float32            `xorm:"-"`
	Size        int64              `xorm:"NOT NULL DEFAULT 0"`
	Color       string             `xorm:"-"`
	CreatedUnix timeutil.TimeStamp `xorm:"INDEX CREATED"`
}

func init() {
	db.RegisterModel(new(LanguageStat))
}

// LanguageStatList defines a list of language statistics
type LanguageStatList []*LanguageStat

// LoadAttributes loads attributes
func (stats LanguageStatList) LoadAttributes() {
	for i := range stats {
		stats[i].Color = enry.GetColor(stats[i].Language)
	}
}

func (stats LanguageStatList) getLanguagePercentages() map[string]float32 {
	langPerc := make(map[string]float32)
	var otherPerc float32
	var total int64

	for _, stat := range stats {
		total += stat.Size
	}
	if total > 0 {
		for _, stat := range stats {
			perc := float32(float64(stat.Size) / float64(total) * 100)
			if perc <= 0.1 {
				otherPerc += perc
				continue
			}
			langPerc[stat.Language] = perc
		}
	}
	if otherPerc > 0 {
		langPerc["other"] = otherPerc
	}
	roundByLargestRemainder(langPerc, 100)
	return langPerc
}

// Rounds to 1 decimal point, target should be the expected sum of percs
func roundByLargestRemainder(percs map[string]float32, target float32) {
	leftToDistribute := int(target * 10)

	keys := make([]string, 0, len(percs))

	for k, v := range percs {
		percs[k] = v * 10
		floored := math.Floor(float64(percs[k]))
		leftToDistribute -= int(floored)
		keys = append(keys, k)
	}

	// Sort the keys by the largest remainder
	sort.SliceStable(keys, func(i, j int) bool {
		_, remainderI := math.Modf(float64(percs[keys[i]]))
		_, remainderJ := math.Modf(float64(percs[keys[j]]))
		return remainderI > remainderJ
	})

	// Increment the values in order of largest remainder
	for _, k := range keys {
		percs[k] = float32(math.Floor(float64(percs[k])))
		if leftToDistribute > 0 {
			percs[k]++
			leftToDistribute--
		}
		percs[k] /= 10
	}
}

// GetLanguageStats returns the language statistics for a repository
func GetLanguageStats(ctx context.Context, repo *Repository) (LanguageStatList, error) {
	stats := make(LanguageStatList, 0, 6)
	if err := db.GetEngine(ctx).Where("`repo_id` = ?", repo.ID).Desc("`size`").Find(&stats); err != nil {
		return nil, err
	}
	return stats, nil
}

// GetTopLanguageStats returns the top language statistics for a repository
func GetTopLanguageStats(ctx context.Context, repo *Repository, limit int) (LanguageStatList, error) {
	stats, err := GetLanguageStats(ctx, repo)
	if err != nil {
		return nil, err
	}
	perc := stats.getLanguagePercentages()
	topstats := make(LanguageStatList, 0, limit)
	var other float32
	for i := range stats {
		if _, ok := perc[stats[i].Language]; !ok {
			continue
		}
		if stats[i].Language == "other" || len(topstats) >= limit {
			other += perc[stats[i].Language]
			continue
		}
		stats[i].Percentage = perc[stats[i].Language]
		topstats = append(topstats, stats[i])
	}
	if other > 0 {
		topstats = append(topstats, &LanguageStat{
			RepoID:     repo.ID,
			Language:   "other",
			Color:      "#cccccc",
			Percentage: float32(math.Round(float64(other)*10) / 10),
		})
	}
	topstats.LoadAttributes()
	return topstats, nil
}

// UpdateLanguageStats updates the language statistics for repository
func UpdateLanguageStats(ctx context.Context, repo *Repository, commitID string, stats map[string]int64) error {
	return db.WithTx(ctx, func(ctx context.Context) error {
		sess := db.GetEngine(ctx)

		oldstats, err := GetLanguageStats(ctx, repo)
		if err != nil {
			return err
		}
		var topLang string
		var s int64
		for lang, size := range stats {
			if size > s {
				s = size
				topLang = lang
			}
		}

		for lang, size := range stats {
			upd := false
			for _, s := range oldstats {
				// Update already existing language
				if strings.EqualFold(s.Language, lang) {
					s.CommitID = commitID
					s.IsPrimary = lang == topLang
					s.Size = size
					if _, err := sess.ID(s.ID).Cols("`commit_id`", "`size`", "`is_primary`").Update(s); err != nil {
						return err
					}
					upd = true
					break
				}
			}
			// Insert new language
			if !upd {
				if err := db.Insert(ctx, &LanguageStat{
					RepoID:    repo.ID,
					CommitID:  commitID,
					IsPrimary: lang == topLang,
					Language:  lang,
					Size:      size,
				}); err != nil {
					return err
				}
			}
		}
		// Delete old languages
		statsToDelete := make([]int64, 0, len(oldstats))
		for _, s := range oldstats {
			if s.CommitID != commitID {
				statsToDelete = append(statsToDelete, s.ID)
			}
		}
		if len(statsToDelete) > 0 {
			if _, err := sess.In("`id`", statsToDelete).Delete(&LanguageStat{}); err != nil {
				return err
			}
		}

		// Update indexer status
		return UpdateIndexerStatus(ctx, repo, RepoIndexerTypeStats, commitID)
	})
}

// CopyLanguageStat Copy originalRepo language stat information to destRepo (use for forked repo)
func CopyLanguageStat(ctx context.Context, originalRepo, destRepo *Repository) error {
	return db.WithTx(ctx, func(ctx context.Context) error {
		RepoLang := make(LanguageStatList, 0, 6)
		if err := db.GetEngine(ctx).Where("`repo_id` = ?", originalRepo.ID).Desc("`size`").Find(&RepoLang); err != nil {
			return err
		}
		if len(RepoLang) > 0 {
			for i := range RepoLang {
				RepoLang[i].ID = 0
				RepoLang[i].RepoID = destRepo.ID
				RepoLang[i].CreatedUnix = timeutil.TimeStampNow()
			}
			// update destRepo's indexer status
			tmpCommitID := RepoLang[0].CommitID
			if err := UpdateIndexerStatus(ctx, destRepo, RepoIndexerTypeStats, tmpCommitID); err != nil {
				return err
			}
			if err := db.Insert(ctx, &RepoLang); err != nil {
				return err
			}
		}
		return nil
	})
}
