package render

import (
	"fmt"
	"symph/game"
	"symph/parameter"
	"symph/types"
	"time"

	"github.com/lixenwraith/color"
)

// Compile-time: one density glyph per wall band
const _ = uint(len(parameter.Density256Chars) - parameter.WallBandCount)

// PlayerBg is the tile-wide background of the player position — deep indigo,
// contrasts against the black field while preserving legibility of every
// foreground band color (yellow/orange/red) and item color
var PlayerBg = color.RGB{R: 32, G: 40, B: 72}

// A held shield charge and an active Boost are field state — immunity must read
// at the point of contact, not only in the HUD. Both fills stay dark: every
// wall band color and item color is high-luminance and must remain legible over
// the player tile
var (
	PlayerShieldBg = color.RGB{R: 40, G: 72, B: 88}
	PlayerBoostBg  = color.RGB{R: 64, G: 48, B: 16}
)

// PlayerBgFor selects the player fill for the active status. Boost outranks
// Shield: it is the effect absorbing the contact
func PlayerBgFor(s game.Status, now time.Time) color.RGB {
	switch {
	case s.Boosted(now):
		return PlayerBoostBg
	case s.Shielded():
		return PlayerShieldBg
	}
	return PlayerBg
}

// RingIdle is the border color of a tile with no wall in the window
var RingIdle = color.Teal

// --- Wall proximity (terminal border encoding) ---

// wallBandColor is indexed by proximity band (0 = arrived)
var wallBandColor = [parameter.WallBandCount]color.RGB{
	color.BrightRed,   // 0: arrived
	color.Vermilion,   // 1: dark orange
	color.TigerOrange, // 2: light orange
	color.Yellow,      // 3: far
}

// WallSolid is the arrived-wall glyph (100% density)
var WallSolid = parameter.Density256Chars[len(parameter.Density256Chars)-1]

// WallBand maps a chord distance to a proximity band (0 = arrived).
// Distances past the last band clamp to it
func WallBand(distance int) int {
	if distance <= 0 {
		return 0
	}
	return min((distance+parameter.WallBandSize-1)/parameter.WallBandSize, parameter.WallBandCount-1)
}

// WallBandColor maps a chord distance to its proximity band color. Band 0
// (arrived) is bright red; receding bands cool through orange to yellow.
// Border fill is binary — a filled ring means the lane is lethal at the
// current chord — so approach urgency rides on ring color alone
func WallBandColor(distance int) color.RGB {
	return wallBandColor[WallBand(distance)]
}

// --- Item / note visuals ---

// valueVisual is the appearance of a Value in the strip and distance row: the
// distant→arrived color ramp. Both endpoints are high-luminance so a distant
// item stays visible against the black field. Item ramps avoid the wall band
// family (red/orange/yellow); unauthored kinds fall back to the dim
// unknownVisual rather than eating an item slot
type valueVisual struct {
	far, near color.RGB
	authored  bool
}

var valueVisuals = [types.ValueCount]valueVisual{
	types.ValueEnergy: {color.BrightCyan, color.BrightGreen, true},
	types.ValueMagnet: {color.Cornflower, color.HotMagenta, true},
	types.ValueShield: {color.CoolSilver, color.White, true},
	types.ValueBoost:  {color.PaleLemon, color.Gold, true},
}

var unknownVisual = valueVisual{color.DimSilver, color.Silver, true}

// TileGlyph resolves the strip and distance-row glyph for a Value at a given chord distance.
// Walls follow the border band encoding so the ring, strip, and distance row agree.
// Items use the morph lerp over their authored ramp
func TileGlyph(v types.Value, distance int) (rune, color.RGB) {
	if v == types.ValueWall {
		return WallSolid, WallBandColor(distance)
	}
	if !v.Valid() || v == types.ValueNone {
		return 0, color.RGB{}
	}
	t := proximity(distance)
	if vis := valueVisuals[v]; vis.authored {
		return v.Glyph(), vis.far.Lerp(vis.near, t)
	}
	return parameter.UnknownChar, unknownVisual.far.Lerp(unknownVisual.near, t)
}

// TileGlyphASCII resolves the glyph for a frontend limited to the 32..126 atlas:
// the wall's density block is substituted with its authoring rune. Colors are
// identical, so the two frontends stay in presentation parity
func TileGlyphASCII(v types.Value, distance int) (rune, color.RGB) {
	ch, c := TileGlyph(v, distance)
	if v == types.ValueWall {
		ch = v.Glyph()
	}
	return ch, c
}

// proximity maps a chord distance to [0,1]: 1 = arrived (distance<=0),
// 0 = at or beyond MorphWindow chords away
func proximity(distance int) float64 {
	if distance <= 0 {
		return 1
	}
	if distance >= parameter.MorphWindow {
		return 0
	}
	return 1 - float64(distance)/float64(parameter.MorphWindow)
}

// --- HUD effect segment ---

// StatusText composes the active-effect HUD segment: the Shield charge glyph
// and the Boost countdown. Glyphs are the ASCII authoring runes, so the string
// is renderable in both atlases. Empty outside a running PhasePlaying — the
// deadlines are frozen there and a ticking countdown would be a lie
func StatusText(s *game.GameState, now time.Time) string {
	if s.Phase != game.PhasePlaying || s.Paused {
		return ""
	}
	out := make([]rune, 0, 8)
	if s.Status.Shielded() {
		out = append(out, types.ValueShield.Glyph())
	}
	if s.Status.Boosted(now) {
		if len(out) > 0 {
			out = append(out, ' ')
		}
		out = append(out, types.ValueBoost.Glyph(), ' ')
		out = append(out, []rune(TimerText(s.Status.BoostRemaining(now)))...)
	}
	return string(out)
}

// StatusColor tints the effect segment with the arrived color of the expiring
// effect — the Boost when one runs, else the Shield
func StatusColor(s *game.GameState, now time.Time) color.RGB {
	if rem := s.Status.BoostRemaining(now); rem > 0 {
		if rem <= parameter.BoostWarnRemaining {
			return BlinkColor(BlinkNegative, now)
		}
		_, c := TileGlyph(types.ValueBoost, 0)
		return c
	}
	_, c := TileGlyph(types.ValueShield, 0)
	return c
}

// --- Consumption burn-out ---

// FadeColor is the burn-out color of a consumed item at progress t in
// [0,1): a white flash, then a sink into the field. Distinguishes consumption
// from the cell scrolling out from under the strip
func FadeColor(v types.Value, t float64) color.RGB {
	_, base := TileGlyph(v, 0)
	if t < parameter.ItemFlashFraction {
		return color.White.Lerp(base, t/parameter.ItemFlashFraction)
	}
	u := (t - parameter.ItemFlashFraction) / (1 - parameter.ItemFlashFraction)
	return base.Lerp(color.Black, u)
}

// FadeVisual adds the glyph collapse for the terminal strip: the item
// glyph holds through the flash, then decays into the rail cell
func FadeVisual(v types.Value, t float64) (rune, color.RGB) {
	glyph, _ := TileGlyph(v, 0)
	if t >= parameter.ItemFlashFraction {
		u := (t - parameter.ItemFlashFraction) / (1 - parameter.ItemFlashFraction)
		if i := int(u * float64(len(parameter.ItemFadeChars)+1)); i > 0 {
			glyph = parameter.ItemFadeChars[min(i-1, len(parameter.ItemFadeChars)-1)]
		}
	}
	return glyph, FadeColor(v, t)
}

// --- Nearest-occurrence blink ---

// Blink pairs for the distance-row group of the tile(s) holding the grid-wide
// nearest occurrence of each polarity. Both endpoints are high-luminance: the
// cue must read as motion, not as a dip to the background
var (
	BlinkPositive = [2]color.RGB{color.White, color.BrightGreen}
	BlinkNegative = [2]color.RGB{color.Yellow, color.BrightRed}
)

// BlinkColor selects the phase color of a pair. Phase is derived from the
// wall clock, not from PlayDeltaZ: the cue must stay legible when the beat
// tightens at higher levels
func BlinkColor(pair [2]color.RGB, now time.Time) color.RGB {
	return pair[(now.UnixNano()/int64(parameter.RenderBlinkPeriod))&1]
}

// --- Text composition (shared by both frontends) ---

// TimerGlyphs is the wall-countdown affix set. The raylib default font
// atlas covers 32..126 only, so it substitutes TimerASCII
type TimerGlyphs struct{ Inbound, Clear, Open, Trap rune }

var (
	TimerUnicode = TimerGlyphs{
		parameter.TimerInboundPrefix, parameter.TimerClearPrefix,
		parameter.TimerOpenSuffix, parameter.TimerTrapSuffix,
	}
	TimerASCII = TimerGlyphs{'v', '^', '+', '!'}
)

// WallTimerText composes the wall countdown for a segment. Inbound
// counts down to closure, clear counts down to the reopen chord. The trap
// marker is not arrival-only: an inbound wall whose reopen gap is a trap is
// flagged on approach. Returns "" when no wall is in the window
func WallTimerText(g TimerGlyphs, s *game.GameState, seg game.WallSegment, now time.Time) (string, color.RGB) {
	if seg.Distance < 0 {
		return "", color.RGB{}
	}

	out := make([]rune, 0, 8)
	fg := WallBandColor(seg.Distance)

	if seg.Distance == 0 {
		out = append(out, g.Clear)
		out = append(out, []rune(TimerText(s.TimeToChordDistance(seg.Run, now)))...)
		if seg.Open {
			out = append(out, g.Open)
		}
		fg = color.White
	} else {
		out = append(out, g.Inbound)
		out = append(out, []rune(TimerText(s.TimeToChordDistance(seg.Distance, now)))...)
	}

	if seg.Next && seg.Gap <= parameter.TrapGapMax {
		out = append(out, g.Trap)
	}
	return string(out), fg
}

// TimerText formats a countdown as "S.s", clamped to
// [0.0, 9.9]. Window * PlayDeltaZ stays under 10s at all levels; the clamp is a guard
func TimerText(d time.Duration) string {
	s := d.Seconds()
	switch {
	case s < 0:
		s = 0
	case s > 9.9:
		s = 9.9
	}
	return fmt.Sprintf("%.1f", s)
}

// DistText formats a chord-distance into RenderDistDigits columns
func DistText(d int) string {
	if d < 0 {
		return ""
	}
	return fmt.Sprintf("%d", min(d, 99))
}