package server

import (
	"fmt"
	"html/template"
	"io/fs"
	"strings"
	"time"
)

var funcs = template.FuncMap{
	"humanTime": humanTime,
	"humanSize": humanSize,
	"sparkline": sparkline,
	"seq":       seq,
	"maxInt":    maxInt,
	"inc":       func(i int) int { return i + 1 },
}

func parseTemplates() (*template.Template, error) {
	t := template.New("").Funcs(funcs)
	err := fs.WalkDir(templateFS, "templates", func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() || !strings.HasSuffix(path, ".html") {
			return nil
		}
		b, err := fs.ReadFile(templateFS, path)
		if err != nil {
			return err
		}
		name := strings.TrimSuffix(strings.TrimPrefix(path, "templates/"), ".html")
		_, err = t.New(name).Parse(string(b))
		return err
	})
	if err != nil {
		return nil, err
	}
	return t, nil
}

func humanTime(v any) string {
	var t time.Time
	switch x := v.(type) {
	case time.Time:
		t = x
	case *time.Time:
		if x == nil {
			return "—"
		}
		t = *x
	default:
		return "—"
	}
	if t.IsZero() {
		return "—"
	}
	d := time.Since(t)
	switch {
	case d < time.Minute:
		return "just now"
	case d < time.Hour:
		return fmt.Sprintf("%dm ago", int(d.Minutes()))
	case d < 24*time.Hour:
		return fmt.Sprintf("%dh ago", int(d.Hours()))
	case d < 30*24*time.Hour:
		return fmt.Sprintf("%dd ago", int(d.Hours()/24))
	default:
		return t.Format("2006-01-02")
	}
}

func humanSize(b int64) string {
	const k = 1024
	switch {
	case b < k:
		return fmt.Sprintf("%d B", b)
	case b < k*k:
		return fmt.Sprintf("%.1f KB", float64(b)/k)
	case b < k*k*k:
		return fmt.Sprintf("%.1f MB", float64(b)/(k*k))
	default:
		return fmt.Sprintf("%.1f GB", float64(b)/(k*k*k))
	}
}

var sparkGlyphs = []rune("▁▂▃▄▅▆▇█")

func sparkline(vals []int64) string {
	if len(vals) == 0 {
		return ""
	}
	var max int64
	for _, v := range vals {
		if v > max {
			max = v
		}
	}
	if max == 0 {
		return strings.Repeat("·", len(vals))
	}
	var b strings.Builder
	for _, v := range vals {
		if v == 0 {
			b.WriteRune('·')
			continue
		}
		idx := int(float64(v)/float64(max)*float64(len(sparkGlyphs)-1) + 0.5)
		if idx < 0 {
			idx = 0
		}
		if idx >= len(sparkGlyphs) {
			idx = len(sparkGlyphs) - 1
		}
		b.WriteRune(sparkGlyphs[idx])
	}
	return b.String()
}

func seq(n int) []int {
	out := make([]int, n)
	for i := range out {
		out[i] = i
	}
	return out
}

func maxInt(a, b int) int {
	if a > b {
		return a
	}
	return b
}