shader_type canvas_item;

// D-059: 3-layer fog shader. Composites over world content.
// Layer 1: Clear (forward cone) — transparent, soft gradient edge
// Layer 2: Explored fog — light overlay indicating "not fresh", art preserved
// Layer 3: Unexplored — solid near-black #12141a

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);

// Soft gradient via 7x7 Gaussian blur on visibility (sigma 2.0).
// Spreads the cone boundary into a 3-4 tile radius gradient for soft 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;

        // Don't bleed gradient 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
            COLOR = vec4(UNEXPLORED_COLOR, 1.0);
        } else {
            // Continuous blend: clear vision (vis=1) -> light fog (vis=0).
            // The Gaussian blur creates a smooth 3-4 tile soft gradient
            // at the cone edge — no hard boundary.

            // Light fog: subtle animated overlay, preserves all art/info
            float noise_val = texture(noise_tex, tile * 0.03 + vec2(time * 0.11, time * 0.07)).r;
            float fog_alpha = 0.28 + noise_val * 0.04;

            // Clarity ramp from the blurred visibility
            float clarity = smoothstep(0.0, 0.85, vis);
            float alpha = mix(fog_alpha, 0.0, clarity);
            vec3 color = mix(DARK_OVERLAY, 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);
        }
    }
}