// Package render turns fetched weather into terminal output. It is pure: no
// network, no clock beyond what it is given, so every rule below is testable.
package render

import (
	"fmt"
	"math"
	"strings"

	"github.com/lukaszkasprzak/prognosis/internal/config"
	"github.com/lukaszkasprzak/prognosis/internal/i18n"
	"github.com/lukaszkasprzak/prognosis/internal/imgw"
	"github.com/lukaszkasprzak/prognosis/internal/openmeteo"
)

// RainInterestPct is the chance of rain below which the mm and rain columns are
// hidden: on a dry day they are a block of zeroes that pushes real content
// sideways.
const RainInterestPct = 20

// View is everything one run needs to render.
type View struct {
	Label      string
	TZ         string
	Rows       []openmeteo.Row
	Sun        map[string][2]string
	Daily      map[string]float64
	Pollen     map[string]float64
	Warnings   []imgw.Warning
	WarnNote   string
	WarnFailed bool
}

type ctx struct {
	cfg   config.Config
	cat   *i18n.Catalog
	c     func(string, string) string
	width int
	wet   bool
}

// celsius converts a displayed temperature back to Celsius.
//
// IMGW's thresholds are defined in Celsius, so they must be compared in
// Celsius: a warning threshold does not move because the display was switched
// to Fahrenheit. Without this, 85F (a mild 29C) renders in the "IMGW would warn
// about this" red.
func (x ctx) celsius(v float64) float64 {
	if x.cfg.Units == "imperial" {
		return (v - 32) * 5 / 9
	}
	return v
}

// Render produces the whole output.
func Render(v View, cfg config.Config, width int, colour bool) string {
	cx := ctx{
		cfg:   cfg,
		cat:   i18n.For(cfg.DisplayLang),
		c:     Styler(colour),
		width: width,
		wet:   isWet(v.Rows),
	}
	var out []string
	out = append(out, cx.warnings(v)...)
	out = append(out, cx.header(v)...)
	out = append(out, cx.table(v)...)
	if cfg.Graph {
		out = append(out, cx.chart(v)...)
	}
	text := strings.Join(out, "\n")
	// Applied last, one character for one, so the layout above is unaffected.
	if cfg.ASCII {
		text = ASCII(text, cfg.Units)
	}
	return text
}

func isWet(rows []openmeteo.Row) bool {
	for _, r := range rows {
		if mm, ok := r.Val("precipitation"); ok && mm > 0 {
			return true
		}
		if p, ok := r.Val("precipitation_probability"); ok && p >= RainInterestPct {
			return true
		}
	}
	return false
}

// warnings renders IMGW warnings, or an explicit line saying why none are shown.
//
// WarnFailed must never look the same as "none in force": silence would be read
// as all-clear.
func (x ctx) warnings(v View) []string {
	var out []string
	switch {
	case x.WarnDisabled():
		return nil
	case v.WarnFailed:
		out = append(out, x.c(Dim, " "+x.cat.Word("warnings")+": "+x.cat.Word("could_not_check")))
	case v.WarnNote != "":
		out = append(out, x.c(Dim, " "+x.cat.Word("warnings")+": "+v.WarnNote))
	}
	for _, w := range v.Warnings {
		style := Yellow
		switch w.Level {
		case "2":
			style = Red
		case "3":
			style = Bold + ";" + Red
		}
		head := fmt.Sprintf(" ! %s  %s %s  %s -> %s  (%s%%)",
			w.Event, x.cat.Word("level"), w.Level,
			clip(w.From), clip(w.To), w.Probability)
		out = append(out, x.c(style, head))
		for _, line := range wrap(w.Text, x.width) {
			out = append(out, x.c(Dim, "   "+line))
		}
	}
	if len(out) > 0 {
		out = append(out, "")
	}
	return out
}

// WarnDisabled reports whether warnings were switched off in config.
func (x ctx) WarnDisabled() bool { return !x.cfg.Warnings }

// clip shortens "2026-08-10 11:00:00" to "08-10 11:00".
func clip(s string) string {
	if len(s) >= 16 {
		return s[5:16]
	}
	return s
}

func (x ctx) header(v View) []string {
	var out []string
	first := v.Rows[0].When
	title := v.Label + "   " + x.cat.Date(first)
	if x.cfg.Minimal {
		// Just the place and the date: no sun times, no summary, no pollen.
		return append(out, x.c(Bold, title))
	}
	sun, hasSun := v.Sun[first.Format("2006-01-02")]
	suffix := ""
	if hasSun {
		suffix = fmt.Sprintf("   %s %s  %s %s",
			sun[0], x.cat.Word("up"), sun[1], x.cat.Word("down"))
	}
	tz := ""
	if v.TZ != "" {
		tz = "  " + v.TZ
	}
	// Keep it to one line where it fits; a phone is narrow enough that it often
	// does not, and a wrapped title reads worse than two deliberate lines.
	if hasSun && DisplayWidth(title)+DisplayWidth(suffix)+DisplayWidth(tz) <= x.width {
		out = append(out, x.c(Bold, title)+x.c(Dim, suffix+tz))
	} else {
		out = append(out, x.c(Bold, title)+x.c(Dim, tz))
		if hasSun {
			out = append(out, x.c(Dim, fmt.Sprintf(" %s  %s %s   %s %s",
				x.cat.Word("sun"), sun[0], x.cat.Word("up"), sun[1], x.cat.Word("down"))))
		}
	}

	if len(v.Daily) > 0 {
		var bits []string
		lo, okLo := v.Daily["temperature_2m_min"]
		hi, okHi := v.Daily["temperature_2m_max"]
		if okLo && okHi {
			bits = append(bits, fmt.Sprintf("%d-%d°", Deg(lo), Deg(hi)))
		}
		if mm, ok := v.Daily["precipitation_sum"]; ok {
			if mm == 0 {
				bits = append(bits, x.cat.Word("dry"))
			} else {
				bits = append(bits, fmt.Sprintf("%s %.1fmm %s %.0fh",
					x.cat.Word("rainfall"), mm, x.cat.Word("over"),
					v.Daily["precipitation_hours"]))
			}
		}
		if sun, ok := v.Daily["sunshine_duration"]; ok {
			if day, ok2 := v.Daily["daylight_duration"]; ok2 {
				bits = append(bits, fmt.Sprintf("%s %s %s %s %s",
					x.cat.Word("sun"), hm(sun), x.cat.Word("of"), hm(day),
					x.cat.Word("daylight")))
			}
		}
		label := " " + Pad(x.cat.Word("day"), 6) + " "
		// Joined with wide separators when it fits; only a line too long for the
		// terminal is re-wrapped, and then on single spaces.
		joined := strings.Join(bits, "   ")
		lines := []string{joined}
		if DisplayWidth(label)+DisplayWidth(joined) > x.width {
			lines = wrap(joined, x.width-DisplayWidth(label))
		}
		for i, line := range lines {
			prefix := label
			if i > 0 {
				prefix = strings.Repeat(" ", DisplayWidth(label))
			}
			out = append(out, x.c(Dim, prefix+line))
		}
	}

	if len(v.Pollen) > 0 {
		var bits []string
		for _, s := range sortedByValue(v.Pollen) {
			band := PollenBand(s, v.Pollen[s])
			// Skip taxa that are simply absent, but never hide grass: it is the
			// one someone may be allergic to and its absence is information.
			if band == "none" && s != "grass" {
				continue
			}
			text := fmt.Sprintf("%s %.1f", x.cat.Species(s), v.Pollen[s])
			if band != "" {
				text += " " + x.cat.Band(band)
			}
			bits = append(bits, text)
		}
		if len(bits) > 0 {
			if len(bits) > 4 {
				bits = bits[:4]
			}
			out = append(out, x.c(Dim, " "+Pad(x.cat.Word("pollen"), 6)+" ")+strings.Join(bits, "  "))
		}
	}
	return out
}

func hm(seconds float64) string {
	s := int(seconds)
	return fmt.Sprintf("%dh%02dm", s/3600, (s%3600)/60)
}

func sortedByValue(m map[string]float64) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	for i := 1; i < len(keys); i++ {
		for j := i; j > 0 && m[keys[j]] > m[keys[j-1]]; j-- {
			keys[j], keys[j-1] = keys[j-1], keys[j]
		}
	}
	return keys
}

func wrap(text string, width int) []string {
	if width < 8 {
		width = 8
	}
	var lines []string
	var line string
	for _, word := range strings.Fields(text) {
		switch {
		case line == "":
			line = word
		case DisplayWidth(line)+1+DisplayWidth(word) <= width:
			line += " " + word
		default:
			lines = append(lines, line)
			line = word
		}
	}
	if line != "" {
		lines = append(lines, line)
	}
	return lines
}

func round1(v float64) string { return fmt.Sprintf("%.1f", v) }

func compass(deg float64) string {
	dirs := []string{"↓", "↙", "←", "↖", "↑", "↗", "→", "↘"}
	i := int(math.Mod(math.Round(deg/45), 8))
	if i < 0 {
		i += 8
	}
	return dirs[i]
}