shader_type canvas_item;

// D-059/D-015: 3-state fog shader (simplified from 5-layer by #569).
// State 1: Clear (forward cone) — transparent, soft Gaussian gradient edge (3-4 tile radius)
// State 2: Explored (out of cone) — light fog overlay, alpha 0.25-0.35, zone temperature tint,
//          8-10s Perlin breathe. Art and information preserved, just "not fresh" (D-015).
// 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;  // nearest: zones have hard boundaries (D-073)
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
uniform bool debug_exploration = false; // When true, render raw exploration texture

const vec3 UNEXPLORED_COLOR = vec3(0.071, 0.078, 0.102);  // #12141a

// 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 = 2.0 / 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;
}

// Soft gradient on exploration boundary (5x5, sigma 1.5).
// Prevents hard tile-stepped staircase at explored/unexplored edge.
float sample_exploration(vec2 uv) {
    vec2 t = 1.0 / map_size;
    float sum = 0.0;
    float weight = 0.0;
    for (float dy = -2.0; dy <= 2.0; dy += 1.0) {
        for (float dx = -2.0; dx <= 2.0; dx += 1.0) {
            float w = exp(-(dx * dx + dy * dy) / 4.5);
            vec2 sample_uv = clamp(uv + vec2(dx, dy) * t, vec2(0.0), vec2(1.0));
            sum += texture(exploration_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
    // Note: no early return — fragment() in OpenGL3 compat doesn't support return.
    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);

    // Debug mode: render raw exploration texture (bypass fog rendering).
    // Green = EXP_VISIBLE (255), blue = EXP_EXPLORED (128), red = EXP_UNEXPLORED (0).
    } else if (debug_exploration) {
        float explored_dbg = texture(exploration_tex, tex_uv).r;
        if (explored_dbg > 0.9) {
            COLOR = vec4(0.0, explored_dbg, 0.0, 0.8);       // Green: currently visible
        } else if (explored_dbg > 0.1) {
            COLOR = vec4(0.0, 0.0, explored_dbg * 2.0, 0.8);  // Blue: explored
        } else {
            COLOR = vec4(0.5, 0.0, 0.0, 0.8);                 // Red: unexplored
        }

    } else {
        float vis_raw = texture(visibility_tex, tex_uv).r;
        float vis = sample_visibility(tex_uv);
        float explored_raw = texture(exploration_tex, tex_uv).r;
        float explored = sample_exploration(tex_uv);

        // Prevent gradient bleed into never-explored tiles (use raw, unblurred value)
        if (explored_raw < 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 {
            // Fog noise — 8-10s breathe cycle, ±0.05 symmetric around baseline
            float noise_val = texture(noise_tex, tile * 0.03 + vec2(time * 0.11, time * 0.07)).r;
            float fog_alpha = 0.30 + (noise_val * 2.0 - 1.0) * 0.05;  // 0.25-0.35

            // Zone temperature tint (D-046/D-077): subtle warm/cool/neutral per zone
            vec3 zone_tint = texture(zone_tint_tex, tex_uv).rgb;

            // Clarity ramp: transparent inside cone, light fog at edges and beyond
            float clarity = smoothstep(0.0, 0.85, vis);
            float alpha = mix(fog_alpha, 0.0, clarity);
            vec3 color = mix(zone_tint, vec3(0.0), clarity);

            // Soft edge between explored and unexplored (blurred to avoid staircase)
            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);
        }
    }
}