package engine

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/cdnutter/playlink/internal/store"
)

// Layout warnings flag real layout problems only. Content that exists in just
// one library is normal (a singles library naturally has artists and songs
// the albums library lacks), so it is never counted against the layout.

var accentFold = strings.NewReplacer(
	"á", "a", "à", "a", "â", "a", "ä", "a", "ã", "a", "å", "a", "é", "e", "è", "e", "ê", "e", "ë", "e",
	"í", "i", "ì", "i", "î", "i", "ï", "i", "ó", "o", "ò", "o", "ô", "o", "ö", "o", "õ", "o", "ø", "o",
	"ú", "u", "ù", "u", "û", "u", "ü", "u", "ñ", "n", "ç", "c", "ý", "y", "ÿ", "y", "œ", "oe", "æ", "ae", "ß", "ss",
)

// folderKey identifies a folder name regardless of case, punctuation, accents,
// "&" vs "and" and a leading/trailing "The": "AC/DC", "AC-DC" and "ACDC", or
// "The Beatles" and "Beatles, The", get the same key.
func folderKey(name string) string {
	s := accentFold.Replace(strings.ToLower(strings.TrimSpace(name)))
	s = strings.ReplaceAll(s, "&", " and ")
	s = strings.TrimPrefix(s, "the ")
	s = strings.TrimSuffix(s, ", the")
	var b strings.Builder
	for _, w := range words(s) {
		b.WriteString(w)
	}
	return b.String()
}

func subdirs(dir string) []string {
	ents, _ := os.ReadDir(dir)
	var out []string
	for _, en := range ents {
		if en.IsDir() && !strings.HasPrefix(en.Name(), ".") {
			out = append(out, en.Name())
		}
	}
	return out
}

// renamedFolders finds slave folders that are the same folder as a master
// folder under a different name. It checks top-level folders and, for
// top-level folders both libraries share, the folders inside them.
func renamedFolders(l *libs) [][2]string {
	var out [][2]string
	compare := func(prefix string, master, slave []string) {
		exact := map[string]bool{}
		byKey := map[string]string{}
		for _, m := range master {
			exact[m] = true
			if k := folderKey(m); k != "" {
				byKey[k] = m
			}
		}
		for _, s := range slave {
			if exact[s] {
				continue
			}
			if m, ok := byKey[folderKey(s)]; ok {
				out = append(out, [2]string{filepath.Join(prefix, s), filepath.Join(prefix, m)})
			}
		}
	}
	mTop, sTop := subdirs(l.master.Path), subdirs(l.slave.Path)
	compare("", mTop, sTop)
	shared := map[string]bool{}
	for _, m := range mTop {
		shared[m] = true
	}
	for _, s := range sTop {
		if shared[s] {
			compare(s, subdirs(filepath.Join(l.master.Path, s)), subdirs(filepath.Join(l.slave.Path, s)))
		}
	}
	sort.Slice(out, func(i, j int) bool { return out[i][0] < out[j][0] })
	return out
}

func renamedWarning(pairs [][2]string) string {
	if len(pairs) == 0 {
		return ""
	}
	var ex []string
	for _, p := range pairs[:min(3, len(pairs))] {
		ex = append(ex, fmt.Sprintf("%q (slave) vs %q (master)", p[0], p[1]))
	}
	more := ""
	if len(pairs) > 3 {
		more = fmt.Sprintf(" and %d more", len(pairs)-3)
	}
	noun := "folder is"
	if len(pairs) > 1 {
		noun = "folders are"
	}
	return fmt.Sprintf("%d %s named differently in the two libraries: %s%s. Songs inside them only match by path "+
		"once the names agree.", len(pairs), noun, strings.Join(ex, ", "), more)
}

// layoutStats watches, during a scan, where songs found in both libraries
// live. Songs only in the slave library are ignored.
type layoutStats struct {
	shared  int         // slave files with a master counterpart
	moved   int         // ...that live in a different folder in the master
	example [][2]string // a few moved examples
}

func (ls *layoutStats) add(relSlave, relMaster, kind, reason string) {
	if kind == store.KindNone || relMaster == "" {
		return
	}
	ls.shared++
	if kind != store.KindElsewhere && kind != store.KindApprox {
		return
	}
	if albumKey(relSlave) == albumKey(relMaster) {
		return // only a disc folder differs
	}
	// A single, EP or compilation matched to its album version is the
	// intended behaviour, not a layout problem.
	if st := parseTitle(relSlave); st.single || st.compilation || strings.Contains(reason, "album version preferred") {
		return
	}
	ls.moved++
	if len(ls.example) < 2 {
		ls.example = append(ls.example, [2]string{relSlave, relMaster})
	}
}

func (ls *layoutStats) warning() string {
	if ls.shared < 20 || ls.moved*4 <= ls.shared {
		return ""
	}
	var ex []string
	for _, e := range ls.example {
		ex = append(ex, fmt.Sprintf("%q is at %q", e[0], e[1]))
	}
	return fmt.Sprintf("Of %d songs found in both libraries, %d are in a different folder in the master library (for example %s). "+
		"The libraries seem to use different folder layouts, so these songs only match through the fallbacks.",
		ls.shared, ls.moved, strings.Join(ex, "; "))
}