#ifndef WORLD_WETNESS_H
#define WORLD_WETNESS_H

/*
 * Water in and on the ground.
 *
 * Poured water (hose, watering can, pee) lands on the surface, runs
 * downhill, gathers in hollows and trampled paths and soaks in as fast and
 * as far as the soil takes it: asphalt and concrete take nothing, gravel
 * swallows it, a dirt track or the trodden yard only slowly. Wet soil
 * darkens; bare soft ground turns to mud (walking on it makes it worse).
 * It all dries again over hours. Pee leaves a stain and a smell until it
 * fades or is washed out.
 *
 * The ground is cut into cells of 1/6 m; only chunks that got wet are kept.
 */

#include <stdbool.h>
#include <stdio.h>

#include "core/gl.h"

/* What the ground is made of: how much water it holds, how fast it soaks in, whether it turns to mud. */
typedef enum {
    SOIL_MEADOW,  /* loam under grass */
    SOIL_YARD,    /* trodden earth */
    SOIL_TRACK,   /* dirt track */
    SOIL_FIELD,   /* ploughed */
    SOIL_FOREST,  /* needles and humus */
    SOIL_GRAVEL,
    SOIL_PAVED,   /* asphalt, concrete */
    SOIL_COUNT
} Soil;

struct WetChunk;

typedef struct {
    struct WetChunk **chunks;    /* WET_CHUNKS^2, NULL where it's dry */
    int              *live;      /* indices of the chunks in use */
    int               live_count;
    GLuint            texture;   /* RGBA8: soil moisture, standing water, pee, mud */
    float             flow_time; /* real seconds not yet simulated */
    float             slow_time, slow_game;
} Wetness;

struct Terrain;

bool  Wetness_init(Wetness *w);
/* Saves: the wet ground (each chunk in use: water, soil, pee, mud) out to /
   in from a file. Reading needs the terrain (and its wear) in place first. */
bool  Wetness_write(const Wetness *w, FILE *f);
bool  Wetness_read(struct Terrain *t, FILE *f);
void  Wetness_destroy(Wetness *w);

/* Liters landing on the ground around (x, z); pee: how much of it is pee (0..1). */
void  Wetness_pour(struct Terrain *t, float x, float z, float liters, float radius, float pee);

/* Runs the water (dt real seconds) and soaks, dries and fades (game_dt game seconds). */
void  Wetness_update(struct Terrain *t, float dt, float game_dt);

/* Uploads what changed to the texture. */
void  Wetness_sync(Wetness *w);

/* How muddy (0..1). */
float Wetness_mud(const Wetness *w, float x, float z);
/* Standing water here (mm). */
float Wetness_water(const Wetness *w, float x, float z);
/* How soft and wet for trampling (0..1): wet soil that can turn to mud. */
float Wetness_softness(const Wetness *w, float x, float z);
/* The strongest pee smell within radius (0..1). */
float Wetness_pee(const Wetness *w, float x, float z, float radius);

/* A footstep: squelches wet soft ground into mud. Returns how muddy it was (0..1). */
float Wetness_step(Wetness *w, float x, float z);

#endif /* WORLD_WETNESS_H */