package coreindex

import (
	"errors"
	"fmt"
	"io/ioutil"
	"path/filepath"
	"sort"
	"strconv"
	"time"

	util "gitlab.dms3.io/dms3/go-dms3-util"
	idxconfig "gitlab.dms3.io/is/go-idx-config"
)

//
// local filesystem repository file folder hierarchy.
//
// index <repo root>, cfg parameter Indexer.Path, must be a relative path
// 	  - <index>
// reposet root
// 	  - <index>/reposet
// reposet kind root
//	  - <index>/reposet/<kind>
// 	  - <index>/reposet/<kind>/params, not a cfg parameter
//      common params file for all repos of a kind
// 	  - <index>/reposet/<kind>/stopword, optional, not in cfg, nor cli option
// reposet root folder
// 	  - <index>/reposet/<kind>/<name>
//      store name is prefixed with "infostore-" or "metastore-"
// repo root folder and sub-folders, not a cfg parameter
// 	  - <index>/reposet/<kind>/<name>/<number>
//	  - <index>/reposet/<kind>/<name>/<number>/corpus, cfg parameter Indexer.Corpus.Path
//	  - <index>/reposet/<kind>/<name>/<number>/metadata, cfg parameter Indexer.Corpus.Metadata
//    - repo name, composed as:
//	    - window: uint64,    // creation time (Unix, seconds), sharding tag
//	    - area: uint8,       // area number, sharding tag
//	    - cat: uint8,        // category number, sharding tag
//	    - offset: int64,     // time since creation (seconds), recovery tag
//

func ReposetExists(kind, name string) (found bool, path string, err error) {
	if kind == "" {
		err = errors.New("reposet kind must not be null.")
		return
	}
	if name == "" {
		err = errors.New("reposet name must not be null.")
		return
	}
	if path, err = ReposetLocalPath(kind, name); err != nil {
		return
	}
	found = PathExists(path)
	return
}

func PathExists(p string) bool {
	if !util.FileExists(p) {
		return false
	}
	return true
}

func ReposetLocalPath(kind, name string) (path string, err error) {
	var rootpath string
	if rootpath, err = idxconfig.PathRoot(); err != nil {
		return
	}
	path = filepath.Join(rootpath, "reposet", kind, name)
	return
}

func ParamsLocalFile(kind string) (path string, err error) {
	var rootpath string
	if rootpath, err = idxconfig.PathRoot(); err != nil {
		return
	}
	path = filepath.Join(rootpath, "reposet", kind, "params")
	return
}

func StopwordsLocalFile(kind string) (path string, err error) {
	var rootpath string
	if rootpath, err = idxconfig.PathRoot(); err != nil {
		return
	}
	path = filepath.Join(rootpath, "stopwords")
	if !PathExists(path) {
		err = fmt.Errorf("stopwords file is missing, must be generated at %v\n", path)
		return
	}
	return
}

// get count of repos in a reposet.
func GetRepoCount(reposetPath string) (repoCount int) {

	// get list of repo entries in reposet
	files, err := ioutil.ReadDir(reposetPath)
	if err != nil {
		return
	}

	// repos form an ordered sequential set from 1 to a limit of 255.
	// we ignore holes in the ordered set (when repos are manually deleted
	// on disk).
	rs := new([255]int)

	// filter non-numeric sub-folders, and out of range repo numbers
	for _, file := range files {
		if file.IsDir() {
			i, err := strconv.Atoi(file.Name())
			if err == nil && i > 0 && i < 256 {
				rs[i-1] = i
			}
		}
	}

	// sort repo numbers, don't rely on os ordering
	s := rs[0:255]
	sort.Ints(s)

	// return largest repo number up to valid limit
	repoCount = s[len(s)-1]

	return
}

// path to next repo number in reposet
func NextRepoPath(reposetPath string, repoCount int) (repoPath string) {

	if repoCount >= 0 && repoCount < 255 {
		repoPath = filepath.Join(reposetPath, strconv.Itoa(repoCount+1))
	} else {
		repoPath = ""
	}
	return
}

// not used, but keep for reference
// index folders under repoRootPath are managed by infospace
func repoName(repoRootPath string) (reponame string, createtime time.Time) {

	t := time.Now() // repo create time
	o := t.Sub(t)   // seconds since repo create (zero at creation time)
	a := 0          // current area (zero ==> none)
	c := 0          // current category (zero ==> none)
	createtime = t

	window := fmt.Sprintf("w%d", t.Unix()) // seconds since Unix epoch
	area := fmt.Sprintf("-a%d", a+1)       // start at 1. 0 ==> N/A
	category := fmt.Sprintf("-c%d", c+1)   // start at 1. 0 ==> N/A
	offset := fmt.Sprintf("-o%d", o)       // 0 offset is ok

	reponame = window + area + category + offset

	return
}