package utils

import (
	"math"
	"strconv"
	"strings"
	"time"
)

// ParseLatLng reads the coordinate strings this schema stores — customers,
// customerlocations and tenantlocations all hold latitude/longitude as text
// — and says whether they name a real place.
//
// "0,0" is rejected along with blanks: nothing on this platform is in the
// Gulf of Guinea, and it is what an empty map picker saves.
func ParseLatLng(lat, lng string) (float64, float64, bool) {
	la, err1 := strconv.ParseFloat(strings.TrimSpace(lat), 64)
	lo, err2 := strconv.ParseFloat(strings.TrimSpace(lng), 64)
	if err1 != nil || err2 != nil {
		return 0, 0, false
	}
	if la < -90 || la > 90 || lo < -180 || lo > 180 || (la == 0 && lo == 0) {
		return 0, 0, false
	}
	return la, lo, true
}

// HaversineKm is the great-circle distance between two points.
func HaversineKm(lat1, lng1, lat2, lng2 float64) float64 {
	const earthRadiusKm = 6371.0
	toRad := func(d float64) float64 { return d * math.Pi / 180 }

	dLat := toRad(lat2 - lat1)
	dLng := toRad(lng2 - lng1)
	a := math.Sin(dLat/2)*math.Sin(dLat/2) +
		math.Cos(toRad(lat1))*math.Cos(toRad(lat2))*math.Sin(dLng/2)*math.Sin(dLng/2)
	return 2 * earthRadiusKm * math.Asin(math.Sqrt(a))
}

// OpenNow reads tenantlocations.opentime/closetime ("09:00", "21:30",
// "9:00 AM") against the wall clock. Unparsable or blank hours are treated as
// open: a shop that never filled the field in should not vanish from the
// list, and the ordering flow re-checks at checkout anyway.
func OpenNow(open, closeAt string, now time.Time) bool {
	o, ok1 := parseClock(open)
	c, ok2 := parseClock(closeAt)
	if !ok1 || !ok2 || o == c {
		return true
	}
	cur := now.Hour()*60 + now.Minute()
	if o < c {
		return cur >= o && cur < c
	}
	// Past midnight: "20:00" – "02:00".
	return cur >= o || cur < c
}

func parseClock(s string) (int, bool) {
	s = strings.TrimSpace(s)
	if s == "" {
		return 0, false
	}
	for _, layout := range []string{"15:04", "15:04:05", "3:04 PM", "3:04PM", "03:04 PM", "15.04"} {
		if t, err := time.Parse(layout, strings.ToUpper(s)); err == nil {
			return t.Hour()*60 + t.Minute(), true
		}
	}
	return 0, false
}

// SearchTokens splits a label into the words worth matching on: lowercased,
// punctuation stripped, pack-size noise dropped. "Milk Bikis 100g" →
// ["milk", "bikis"]; the size is matched separately, if at all.
//
// A single character is kept when it follows a word, because in this
// catalogue that character is often the whole product: the "G" in "Parle G",
// the "K" in "Special K". Dropping it made "Parle G" score the same against
// "Parle-G Original Glucose Biscuits" as against "Parle Monaco Classic", and
// the tie went to Monaco. It is still dropped when it stands alone — a
// one-letter label is not a search — and bare multipliers ("2 x 50gm") are
// never words.
func SearchTokens(label string) []string {
	var tokens []string
	seen := make(map[string]bool)
	kept := 0 // multi-character tokens so far: a lone letter needs one
	var filler []string // packaging words, kept only if nothing else survives
	for _, raw := range strings.FieldsFunc(strings.ToLower(label), func(r rune) bool {
		return !(r >= 'a' && r <= 'z' || r >= '0' && r <= '9')
	}) {
		if isPackSize(raw) || seen[raw] {
			continue
		}
		if len(raw) < 2 && (kept == 0 || isMultiplier(raw)) {
			continue
		}
		seen[raw] = true
		if isPackaging(raw) {
			filler = append(filler, raw)
			continue
		}
		if len(raw) > 1 {
			kept++
		}
		tokens = append(tokens, raw)
	}
	// "Dettol bottle pack" is a scan of Dettol. Only when the label is nothing
	// but packaging does that packaging become the search.
	if len(tokens) == 0 {
		return filler
	}
	return tokens
}

// isPackaging is what the label says about the wrapper rather than the
// product: "Dettol bottle pack", "Parle G biscuit pack". Lens reads these off
// the packet and no catalogue name carries them, so every one of them used to
// be a word the row had to contain — and "Dettol bottle pack" found no Dettol
// at all. Treated like pack sizes: real words, just not the product's name.
func isPackaging(tok string) bool {
	switch tok {
	case "pack", "packs", "packet", "packets", "bottle", "bottles",
		"box", "boxes", "jar", "jars", "tin", "tins", "pouch", "pouches",
		"carton", "cartons", "sachet", "sachets", "combo", "refill":
		return true
	}
	return false
}

// isMultiplier is the "x" of "2 x 50gm" and the "n" of a multipack — a single
// character that joins sizes rather than naming a product.
func isMultiplier(tok string) bool {
	return tok == "x" || tok == "n"
}

// FoldSeparators turns every run of punctuation into one space, so a label
// typed without the brand's own punctuation still matches it: "Parle G" and
// "Parle-G" both fold to "parle g". Lens reads letterforms off a packet, and
// people type what they see, so the hyphen is not reliably either present or
// absent on the way in.
func FoldSeparators(s string) string {
	return strings.Join(strings.FieldsFunc(strings.ToLower(s), func(r rune) bool {
		return !(r >= 'a' && r <= 'z' || r >= '0' && r <= '9')
	}), " ")
}

// TightenLabel removes separators outright rather than folding them, catching
// the other way people write a hyphenated name: "ParleG" against "Parle-G".
func TightenLabel(s string) string {
	return strings.ReplaceAll(FoldSeparators(s), " ", "")
}

// isPackSize is "100g", "1kg", "500ml", "2l", "250gm" — a number with a unit
// glued on, or a bare number.
func isPackSize(tok string) bool {
	digits := 0
	for digits < len(tok) && tok[digits] >= '0' && tok[digits] <= '9' {
		digits++
	}
	if digits == 0 {
		return false
	}
	switch tok[digits:] {
	case "", "g", "gm", "gms", "kg", "ml", "l", "ltr", "pcs", "pc", "x", "n":
		return true
	}
	return false
}