#pragma once

#include <cstdint>

#include <etl/vector.h>
#include <mtl/fixed.hpp>
#include <mtl/vec.hpp>
#include <mtl/mat.hpp>
#include <mtl/exception.hpp>

// TODO: Implement in MTL and create version that doesn't need cos of the angle
mtl::mat<2, 2> create_rotation(mtl::fixed angle_cos);

namespace fractal {

constexpr size_t g_max_tokens = 16;
constexpr size_t g_max_groups = 8;
constexpr size_t g_max_wgroups = 4;
constexpr size_t g_max_branch_rules = 8;
constexpr size_t g_max_cgroup_tokens = 16;
constexpr size_t g_max_wgroup_weights = 8;
constexpr size_t g_max_match_groups = 8;
constexpr size_t g_max_match_wgroups = 4;

using token_id_t = uint32_t;
using group_id_t = uint32_t;
using weighted_group_id_t = uint32_t;
using branch_rule_id_t = uint32_t;

enum class token_type_e {
	empty,
	walk,
	rotate,
};

struct token_t {
       token_type_e m_type = token_type_e::empty;
       mtl::fixed m_value;
       uint32_t m_mark;
};

struct group_characteristic_t {
	uint32_t m_factor; // Number of groups generated in succession
	etl::vector<token_id_t, g_max_cgroup_tokens> m_token_ids;
};

struct marker_t {
	mtl::vec2 m_pos;
	uint32_t m_id;
};

struct leaf_t {
	group_id_t m_group_id;
	mtl::vec2 m_position;
	mtl::mat<2, 2> m_orientation;
};

struct weighted_leaf_t {
	weighted_group_id_t m_weighed_group_id;
	mtl::vec2 m_position;
	mtl::mat<2, 2> m_orientation;
};

struct group_output_t {
	static constexpr size_t g_max_child_leafs = 16;
	static constexpr size_t g_max_child_markers = 8;

	etl::vector<weighted_leaf_t, g_max_child_leafs> m_child_leafs;
	etl::vector<marker_t, g_max_child_markers> m_child_markers;
};

struct token_match_t {
	etl::vector<group_id_t, g_max_match_groups> m_groups;
	etl::vector<weighted_group_id_t, g_max_match_wgroups> m_wgroups;
};

struct weighted_group_t {
	etl::vector<group_id_t, g_max_wgroup_weights> m_groups;
	etl::vector<uint32_t, g_max_wgroup_weights> m_weights;
	uint32_t m_weight_total; // Total needed for random selection
	// TODO: Control weight additions so m_weight_total = sum(m_weights) is invariant
};

struct branch_rule_t {
	token_id_t m_match;
	bool m_weighted;

	union {
		group_id_t basic;
		weighted_group_id_t weighted;
	} m_group;
};

class ruleset_t {
private:
	etl::vector<token_t, g_max_tokens> m_tokens;
	etl::vector<group_characteristic_t, g_max_groups> m_group_characteristics;
	etl::vector<weighted_group_t, g_max_wgroups> m_weighted_groups;

	etl::vector<branch_rule_t, g_max_branch_rules> m_branch_rules;

public:
	/**
	 * @brief Checks if the maximum number of tokens has been reached
	 *
	 * @ret @c true if the number of tokens in the ruleset equals @c g_max_tokens, @c false otherwise
	 */
	bool tokens_full() const {
		return m_tokens.full();
	}
	bool valid_token(token_id_t tok) const {
		return tok < m_tokens.size();
	}

	/**
	 * @brief Add new token variable that can be used in this ruleset
	 *
	 * @param type   Type of the token to add
	 * @param value  Value of the token, unused if @p type is @c token_type_e::empty
	 *
	 * @ret @c token_id_t of the newly added token, local to this ruleset
	 * 
	 * @exception @c mtl::length_error if the maximum number of tokens is reached
	 */
	token_id_t add_token(token_type_e type, mtl::fixed value = 0, uint32_t mark = 0);

	/**
	 * @brief Checks if the maximum number of group characteristics has been reached
	 *
	 * @ret @c true if the number of group characteristics in the ruleset equals @c g_max_cgroups, @c false otherwise
	 */
	bool group_characteristics_full() const {
		return m_group_characteristics.full();
	}
	bool valid_group_characteristic(group_id_t group) const {
		return group < m_group_characteristics.size();
	}

	/**
	 * @brief Add new group characteristic
	 *
	 * @param tokens  @c etl::ivector of @c token_id_t that should be generated inside this group
	 * @param factor  The number of times the group's tokens are repeatedly generated
	 *
	 * @ret @c group_id_t of the newly added group characteristic, local to this ruleset
	 *
	 * @exception mtl::invalid_argument if an invalid token was encountered
	 * @exception mtl::length_error if the maximum number of groups is reached
	 */
	group_id_t add_group_characteristic(const etl::ivector<token_id_t>& tokens, uint32_t factor = 1);

	/**
	 * @brief Checks if the maximum number of weighted groups has been reached
	 *
	 * @ret @c true if the number of weighted groups in the ruleset equals @c g_max_wgroups, @c false otherwise
	 */
	bool weighted_groups_full() const {
		return m_weighted_groups.full();
	}
	bool valid_weighted_group(weighted_group_id_t wgroup) const {
		return wgroup < m_weighted_groups.size();
	}

	/**
	 * @brief Add new weighted group
	 *
	 * Adds weighted group of groups, where each subgroup has a 
	 * <tt>(weight) / (total weight)</tt> chance of being selected. Weights
	 * are represented as @c uint32_t.
	 *
	 * @param weights  @c etl::ivector of @c etl::pair of @c group_id_t and their corresponding weights
	 *
	 * @ret @c weighted_group_id_t of the newly created group
	 *
	 * @exception @c mtl::invalid_argument if no groups were supplied, or an invalid group was encountered
	 * @exception @c mtl::length_error if the maximum number of groups is reached
	 */
	weighted_group_id_t add_weighted_group(const etl::ivector<etl::pair<group_id_t, uint32_t>>& weights);

	/**
	 * @brief Checks if the maximum number of branch rules has been reached
	 *
	 * @ret @c true if the number of branch rules in the ruleset equals @c g_max_branch_rules, @c false otherwise
	 */
	bool branch_rules_full() const {
		return m_branch_rules.full();
	}

	/**
	 * @brief Add a new unweighted branch rule to the ruleset
	 *
	 * Branch rules describe what groups can be generated given a token.
	 * Branch rules can use either plain groups or weighted groups as their output.
	 *
	 * @param match  Token to match and generate the group in place of
	 * @param group  Group to generate
	 *
	 * @ret @c branch_rule_id_t of the newly added branch rule
	 *
	 * @exception @c mtl::invalid_argument if an invalid token or group was supplied
	 * @exception @c mtl::length_error if the maximum number of branch rules was reached
	 */
	branch_rule_id_t add_branch_rule(token_id_t match, group_id_t group);

	/**
	 * @brief Add a new weighted branch rule to the ruleset
	 *
	 * Branch rules describe what groups can be generated given a token.
	 * Branch rules can use either plain groups or weighted groups as their output.
	 *
	 * @param match   Token to match and generate the group in place of
	 * @param wgroup  Weighted group to select from, only one subgroup is generated
	 *
	 * @ret @c branch_rule_id_t of the newly added branch rule
	 *
	 * @exception @c mtl::invalid_argument if an invalid token or group was supplied
	 * @exception @c mtl::length_error if the maximum number of branch rules was reached
	 */
	branch_rule_id_t add_branch_rule_weighted(token_id_t match, weighted_group_id_t wgroup);


};

class generator_t {
	etl::vector<weighted_group_t, g_max_wgroups> m_weighted_groups;
	etl::vector<group_output_t, g_max_groups> m_group_outputs;
	etl::vector<token_match_t, g_max_tokens> m_token_matches;
	group_id_t m_axiom;

	uint32_t m_gen_num;

public:
	generator_t(const ruleset_t& ruleset);

	/**
	 * @brief Steps one generation, outputting generated markers
	 *
	 * @tparam CONTAINER_T  Container type of @c marker_t that supplies an @c insert member
	 * function taking an iterator and value, @c size , and @c max_size functions
	 *
	 * @param out_markers   Reference to a container to append generated markers to
	 * 
	 * @ret false if there is not enough room for the child leafs (internally)
	 * or there is not enough room for the generated markers in @p out_markers, true otherwise
	 *
	 * Steps one generation of the fractal, and appends any child markers of
	 * the current generation to @p out_markers. If there is not enough room
	 * for all of the child markers, @p out_markers is unmodified. 
	 */
	template <typename CONTAINER_T>
	bool step_generation(CONTAINER_T& out_markers);

	uint32_t generation_num() const { return m_gen_num; }
};

#if 0
class generator_t {
private:
	static constexpr size_t g_max_groups = 32;
	static constexpr size_t g_max_weighted_groups = 32;
	static constexpr size_t g_max_tokens = 32;
	static constexpr size_t g_max_leafs_per_gen = 1024; // Maximum leafs per generation
	static constexpr size_t g_max_rules_basic = 16;
	static constexpr size_t g_max_rules_marking = 4;

	// We are creating two buffers are leafs. One for the current generation
	// and one for the next generation. These will be accessed through current/next
	// ivectors that will point to different buffers as they are swapped.
	etl::vector<leaf_t, g_max_leafs_per_gen> m_leaf_buf1;
	etl::vector<leaf_t, g_max_leafs_per_gen> m_leaf_buf2;

	etl::vector<token_t, g_max_tokens> m_tokens;

	etl::vector<group_characteristic_t, g_max_groups> m_group_characteristics;
	etl::vector<group_t, g_max_groups> m_groups;
	etl::vector<weighted_group_t, g_max_weighted_groups> m_weighted_groups;

	etl::vector<branch_rule_basic_t, g_max_rules_basic> m_basic_branch_rules;
	etl::vector<branch_rule_marking_t, g_max_rules_marking> m_marking_branch_rules;

	etl::ivector<leaf_t>* m_leafs_cur;
	etl::ivector<leaf_t>* m_leafs_next;

	bool m_processed;
	uint32_t m_generation;

	mtl::fixed m_scale_factor;

	weighted_group_id_t m_axiom;
	mtl::vec2 m_init_position;
	mtl::fixed m_init_orientation;

public:
	/**
	 * Default constructor
	 */
	generator_t() noexcept :
		m_leafs_cur(&m_leaf_buf1),
		m_leafs_next(&m_leaf_buf2),
		m_axiom(0),
		m_generation(0),
		m_scale_factor(1),
		m_processed(false) {}

	/**
	 * @brief Add new token variable that can be used in this generator's group characteristics.
	 *
	 * @param type   Type of the token to add
	 * @param value  Value of the token. Unused if @p type is @c token_type_e::generate. Defaults to 0
	 * 
	 * @ret @c token_id_t of the newly added token, local to this generator.
	 *
	 * @pre preprocess() has not been called on this generator.
	 *
	 * @exception mtl::system_error If the generator has already been preprocessed.
	 * @exception mtl::invalid_argument If the given token type is invalid.
	 * @exception mtl::length_error If the maximum number of tokens is reached.
	 */
	token_id_t add_token(token_type_e type, mtl::fixed value = 0);

	/**
	 * @brief Add new group charateristic.
	 *
	 * After all tokens, groups, and rules have been added, the generator's groups
	 * must be processed by calling preprocess(). Once this is done, no new
	 * groups may be added. If an exception occurs, no data is modified.
	 *
	 * @param factor  The number of times the group is repeated. Treats the group as if @p tokens was repeated @p factor number of times.
	 * @param tokens  @c etl::ivector of @token_id_t that describe how the group functions. Processed in order, front to back.
	 *
	 * @ret @c group_id_t of the newly added group, local to this generator.
	 *
	 * @pre preprocess() has not been called on this generator.
	 *
	 * @exception mtl::system_error If the generator has already been preprocessed.
	 * @exception mtl::invalid_argument If an invalid token was encountered.
	 * @exception mtl::length_error If the maximum number of groups is reached.
	 */
	group_id_t add_group_characteristic(uint32_t factor, const etl::ivector<token_id_t>& tokens);
	/**
	 * @overload
	 *
	 * Convience overload, defaulting to a group with factor 1.
	 */
	group_id_t add_group_characteristic(const etl::ivector<token_id_t>& tokens);

	/**
	 * @brief Add a weighted group to the generator.
	 *
	 * Adds weighted group of groups, where each subgroup has a
	 * <tt>(weight) / (total weight)</tt> chance of being selected. Weights
	 * are represented as @c uint32_t. If an exception occurs, no data is modified.
	 *
	 * @param weights  @c etl::ivector of @c etl::pair s of @c group_id_it and their corresponding weights.
	 * 
	 * @ret @c weighted_group_id_t of the newly added group, local to this generator.
	 *
	 * @pre preprocess() has not been called on this generator.
	 *
	 * @exception mtl::invalid_argument If no groups were supplied, or an invalid group was encountered.
	 * @exception mtl::system_error If the generator has already been preprocessed.
	 * @exception mtl::length_error If the maximum number of weighted groups is reached.
	 */
	weighted_group_id_t add_weighted_group(const etl::ivector<etl::pair<group_id_t, uint32_t>>& group_weights);
	/**
	 * @overload
	 *
	 * Convenience overload. Creates a weighted group for a group with only
	 * one possibility.
	 */
	weighted_group_id_t add_weighted_group(group_id_t group);

	/**
	 * @brief Add a basic (non-marking) branch rule to the generator.
	 *
	 * Basic branch rules describe how this generator will create new leafs
	 * each generation.
	 *
	 * @param match   Token to match and generate the group in place of.
	 * @param wgroup  Weighted group to generate. Only one subgroup will be selected to generate.
	 *
	 * @ret @c branch_rule_basic_id_t of the newly added branch rule, local to this generator.
	 *
	 * @pre preprocess() has not been called on this generator.
	 *
	 * @exception mtl::invalid_argument If no groups were supplied, or an invalid group was encountered.
	 * @exception mtl::system_error If the generator has already been preprocessed.
	 * @exception mtl::length_error If the maximum number of basic branch rules is reached.
	 */
	branch_rule_basic_id_t add_basic_branch_rule(token_id_t match, weighted_group_id_t wgroup);

	/**
	 * @brief Add a marking branch rule to the generator.
	 *
	 * Marking branch rules describe what points (markers) this generator
	 * will output to the caller each generator.
	 *
	 * @param match      Token to match and mark.
	 * @param marker_id  ID to mark the point with.
	 *
	 * @ret @c branch_rule_marking_id_t of the newly added branch rule, local to this generator.
	 *
	 * @pre preprocess() has not been called on this generator.
	 *
	 * @exception mtl::invalid_argument If an invalid token was supplied.
	 * @exception mtl::system_error If the generator has already been preprocessed.
	 * @exception mtl::length_error If the maximum number of marking branch rules is reached.
	 */
	branch_rule_marking_id_t add_marking_branch_rule(token_id_t match, uint32_t marker_id);

	/**
	 * @brief Set the axiom used in this generator.
	 *
	 * The "axiom" is used to generate the very first generation of leafs.
	 * Only one subgroup from the weighted group is selected.
	 *
	 * @exception mtl::invalid If an invalid weighted group ID was suppied.
	 */
	void set_axiom(weighted_group_id_t wgroup);

	/**
	 * @brief Perform preprocessing on the supplied group characteristics.
	 * 
	 * Transforms each group, producing a list of child leafs and markers
	 * that should be generated for each group characteristic. Has no effect
	 * if called more than once.
	 *
	 * @pre All tokens, groups characteristics, weighted groups, and branch
	 * rules have been added.
	 *
	 * @exception mtl::length_error If the number of resulting child leafs
	 * or markers exceeds the maximum allowed for one group.
	 */
	void preprocess();

	/**
	 * @brief Set the scale factor used each generation.
	 *
	 * Each time the generation is stepped, the length of each walk is scaled
	 * by @p scale_factor. Can be set to a new value at any time.
	 *
	 * @param scale_factor  The new scale factor to use
	 */
	void set_scale_factor(mtl::fixed scale_factor) noexcept;

	/**
	 * @brief Set the initial position the axiom is generated in.
	 *
	 * @param position  The initial position to use.
	 */
	void set_initial_position(mtl::vec2 position) noexcept;
	/**
	 * @brief Set the initial orientation the axiom is generated in.
	 *
	 * @param orientation  The initial orientation to use. Given in radians.
	 */
	void set_initial_orientation(mtl::fixed orientation) noexcept;

	/**
	 * @brief Steps one generation in the fractal, generating a vector of markers.
	 *
	 * The vector of markers will NOT be cleared at the beginning of generation.
	 *
	 * @param out_markers  An @c etl::ivector of @c marker_t. Each marker
	 * encountered will be appended to this list in the order encountered.
	 *
	 * @ret true if the maximum number of markers was reached, otherwise false.
	 */
	bool step_generation(const etl::ivector<marker_t>& out_markers) noexcept;
};
#endif

} // namespace fractal