shader_type canvas_item;

// D-059: 3-state fog shader (simplified from 5-layer by #569).
// State 1: Clear (forward cone) — transparent, soft Gaussian gradient edge (6-8 tile spread)
// State 2: Explored (out of cone, EXP_EXPLORED) — two sub-zones by vis proximity:
//   a) Light fog (near cone gradient): alpha 0.25-0.35, neutral dark, 8-10s breathe
//   b) Deep fog (far from cone, vis≈0): alpha 0.55-0.70, zone temperature tint, 15-20s breathe
// State 3: Unexplored — solid near-black #12141a
// D-033: Entity colors are NOT affected — they render above the fog overlay (z-layer 5).
// D-046: Zone temperature tint from zone_tint_tex — warm=bar, cool=hub, neutral=corridor.
// D-077: zone_tint_tex populated per-tile from server zone_id via fog_state.gd.

uniform sampler2D visibility_tex : filter_linear, repeat_disable;
uniform sampler2D exploration_tex : filter_linear, repeat_disable;
uniform sampler2D zone_tint_tex : filter_nearest, repeat_disable;
uniform sampler2D noise_tex : filter_linear, repeat_enable;
uniform vec2 rect_pos;       // World-space position of the ColorRect (pixels)
uniform vec2 rect_sz;        // World-space size of the ColorRect (pixels)
uniform vec2 map_offset;     // map_bounds.position (tiles)
uniform vec2 map_size;       // map_bounds.size (tiles)
uniform float tile_size;     // Pixels per sim tile
uniform float time;          // Seconds since start

const vec3 UNEXPLORED_COLOR = vec3(0.071, 0.078, 0.102);  // #12141a
const vec3 DARK_OVERLAY = vec3(0.02, 0.02, 0.05);         // neutral dark (light fog zone)

// Soft gradient via 7x7 Gaussian blur on visibility (sigma 2.0).
// Spreads the cone boundary into a 3-4 tile radius gradient — no hard tile-stepped edges.
float sample_visibility(vec2 uv) {
    vec2 t = 1.0 / map_size;
    float sum = 0.0;
    float weight = 0.0;
    for (float dy = -3.0; dy <= 3.0; dy += 1.0) {
        for (float dx = -3.0; dx <= 3.0; dx += 1.0) {
            float w = exp(-(dx * dx + dy * dy) / 8.0);
            vec2 sample_uv = clamp(uv + vec2(dx, dy) * t, vec2(0.0), vec2(1.0));
            sum += texture(visibility_tex, sample_uv).r * w;
            weight += w;
        }
    }
    return sum / weight;
}

void fragment() {
    vec2 world_px = rect_pos + UV * rect_sz;
    vec2 tile = world_px / tile_size;
    vec2 tex_uv = (tile - map_offset) / map_size;

    // Outside known map -> unexplored
    if (tex_uv.x < 0.0 || tex_uv.x > 1.0 || tex_uv.y < 0.0 || tex_uv.y > 1.0) {
        COLOR = vec4(UNEXPLORED_COLOR, 1.0);
    } else {
        float vis_raw = texture(visibility_tex, tex_uv).r;
        float vis = sample_visibility(tex_uv);
        float explored = texture(exploration_tex, tex_uv).r;

        // Prevent gradient bleed into never-explored tiles
        if (explored < 0.01 && vis_raw < 0.01) {
            vis = 0.0;
        }

        if (explored < 0.01 && vis < 0.01) {
            // Unexplored: solid near-black — information zero
            COLOR = vec4(UNEXPLORED_COLOR, 1.0);
        } else {
            // Light fog noise — fast cycle (~9s), ±0.05 breathing
            float noise_fast = texture(noise_tex, tile * 0.03 + vec2(time * 0.11, time * 0.07)).r;
            // Deep fog noise — slow cycle (~20s), ±0.075 breathing (more pronounced)
            float noise_slow = texture(noise_tex, tile * 0.02 + vec2(time * 0.05, time * 0.035)).r;

            // Light fog: alpha 0.25-0.35 (centered at 0.30, ±0.05 breathe)
            // Noise remapped to [-1,+1] for symmetric breathing around baseline.
            float light_fog_alpha = 0.30 + (noise_fast * 2.0 - 1.0) * 0.05;

            // Deep fog: alpha 0.55-0.70 (centered at 0.625, ±0.075 breathe)
            float deep_fog_alpha = 0.625 + (noise_slow * 2.0 - 1.0) * 0.075;

            // Blend deep <-> light fog by proximity to cone:
            //   vis=0   (far from cone)  → deep_factor=1 → deep fog
            //   vis=0.3 (cone gradient)  → deep_factor=0 → light fog
            //   vis=0.85+ (inside cone)  → clarity=1     → transparent (clear)
            float deep_factor = 1.0 - smoothstep(0.0, 0.30, vis);
            float fog_alpha = mix(light_fog_alpha, deep_fog_alpha, deep_factor);

            // Zone temperature tint (D-059/D-046/D-077):
            // Deep fog color uses zone_tint_tex; light fog uses neutral DARK_OVERLAY.
            // zone_tint_tex is populated per-tile from server zone_id via fog_state.gd.
            vec3 zone_tint = texture(zone_tint_tex, tex_uv).rgb;

            // Clarity ramp: transparent inside cone, fogged at edges and beyond
            float clarity = smoothstep(0.0, 0.85, vis);
            float alpha = mix(fog_alpha, 0.0, clarity);

            // Color: deep fog → zone temperature tint; light fog → neutral dark overlay
            vec3 fog_color = mix(DARK_OVERLAY, zone_tint, deep_factor);
            vec3 color = mix(fog_color, vec3(0.0), clarity);

            // Soft edge between explored and unexplored
            float exp_fade = smoothstep(0.0, 0.3, explored);
            alpha = mix(1.0, alpha, exp_fade);
            color = mix(UNEXPLORED_COLOR, color, exp_fade);

            COLOR = vec4(color, alpha);
        }
    }
}