pathfinder = {}

--[[
minetest.get_content_id(name)
minetest.registered_nodes
minetest.get_name_from_content_id(id)
local ivm = a:index(pos.x, pos.y, pos.z)
local ivm = a:indexp(pos)
minetest.hash_node_position({x=,y=,z=})
minetest.get_position_from_hash(hash)

start_index, target_index, current_index
^ Hash of position

current_value
^ {int:hCost, int:gCost, int:fCost, hash:parent, vect:pos}
]]--

local openSet = {}
local closedSet = {}

local function get_distance(start_pos, end_pos)
    local distX = math.abs(start_pos.x - end_pos.x)
    local distZ = math.abs(start_pos.z - end_pos.z)

    if distX > distZ then
        return 14 * distZ + 10 * (distX - distZ)
    else
        return 14 * distX + 10 * (distZ - distX)
    end
end

local function get_distance_to_neighbor(start_pos, end_pos)
    local distX = math.abs(start_pos.x - end_pos.x)
    local distY = math.abs(start_pos.y - end_pos.y)
    local distZ = math.abs(start_pos.z - end_pos.z)

    if distX > distZ then
        return (14 * distZ + 10 * (distX - distZ)) * (distY + 1)
    else
        return (14 * distX + 10 * (distZ - distX)) * (distY + 1)
    end
end

local function walkable(node, pos, current_pos)
        if string.find(node.name,"doors:door") then
            if (node.param2 == 0 or
                    node.param2 == 2) and
                    math.abs(pos.z - current_pos.z) > 0 and
                    pos.x == current_pos.x then
                return true
            elseif (node.param2 == 1 or
                    node.param2 == 3) and
                    math.abs(pos.z - current_pos.z) > 0 and
                    pos.x == current_pos.x then
                return false
            elseif (node.param2 == 0 or
                    node.param2 == 2) and
                    math.abs(pos.x - current_pos.x) > 0 and
                    pos.z == current_pos.z then
                return false
            elseif (node.param2 == 1 or
                    node.param2 == 3) and
                    math.abs(pos.x - current_pos.x) > 0 and
                    pos.z == current_pos.z then
                return true
            end
        elseif string.find(node.name,"doors:hidden") then
            local node_door = minetest.get_node({x = pos.x, y = pos.y - 1, z = pos.z})
            if (node_door.param2 == 0 or
                    node_door.param2 == 2) and
                    math.abs(pos.z - current_pos.z) > 0 and
                    pos.x == current_pos.x then
                return true
            elseif (node_door.param2 == 1 or
                    node_door.param2 == 3) and
                    math.abs(pos.z - current_pos.z) > 0 and
                    pos.x == current_pos.x then
                return false
            elseif (node_door.param2 == 0 or
                    node_door.param2 == 2) and
                    math.abs(pos.x - current_pos.x) > 0 and
                    pos.z == current_pos.z then
                return false
            elseif (node_door.param2 == 1 or
                    node_door.param2 == 3) and
                    math.abs(pos.x - current_pos.x) > 0 and
                    pos.z == current_pos.z then
                return true
            end

        end

        if not minetest.registered_nodes [node.name] then
            return false
        end
        return minetest.registered_nodes [node.name].walkable
end

local function get_neighbor_ground_level(pos, jump_height, fall_height, current_pos)
    local node = minetest.get_node(pos)
    local height = 0
    if walkable(node, pos, current_pos) then
        repeat
            height = height + 1
            if height > jump_height then
                return nil
            end
            pos.y = pos.y + 1
            node = minetest.get_node(pos)
        until not walkable(node, pos, current_pos)
        return pos
    else
        repeat
            height = height + 1
            if height > fall_height then
                return nil
            end
            pos.y = pos.y - 1
            node = minetest.get_node(pos)
        until walkable(node, pos, current_pos)
        return {x = pos.x, y = pos.y + 1, z = pos.z}
    end
end

-- local function dot(a, b)
--  return a.x * b.x + a.y * b.y + a.z * b.z
-- end
--
-- local function len(a)
--   return math.sqrt(a.x * a.x + a.y * a.y + a.z * a.z)
-- end
--
-- local function lensq(a)
--   return a.x * a.x + a.y * a.y + a.z * a.z
-- end
--
-- local function normalize(a)
--   local l = len(a)
--   a.x = a.x / l
--   a.y = a.y / l
--   a.z = a.z / l
--   return a
-- end

function pathfinder.find_path(pos, endpos, entity, dtime)
    -- if dtime > 0.1 then
    --  return
    -- end
    -- round positions if not done by former functions
    pos = {
            x = math.floor(pos.x + 0.5),
            y = math.floor(pos.y + 0.5),
            z = math.floor(pos.z + 0.5)
    }

    endpos = {
            x = math.floor(endpos.x + 0.5),
            y = math.floor(endpos.y + 0.5),
            z = math.floor(endpos.z + 0.5)
    }

    local target_node = minetest.get_node(endpos)
    if walkable(target_node, endpos, endpos) then
        endpos.y = endpos.y + 1
    end

    local start_node = minetest.get_node(pos)
    if string.find(start_node.name,"doors:door") then
        if start_node.param2 == 0 then
            pos.z = pos.z + 1
        elseif start_node.param2 == 1 then
            pos.x = pos.x + 1
        elseif start_node.param2 == 2 then
            pos.z = pos.z - 1
        elseif start_node.param2 == 3 then
            pos.x = pos.x - 1
        end
    end

    local start_time = minetest.get_us_time()
    local start_index = minetest.hash_node_position(pos)
    local target_index = minetest.hash_node_position(endpos)
    local count = 1

    openSet = {}
    closedSet = {}
    -- minetest.set_node(pos, {name = "default:glass"})
    -- minetest.set_node(endpos, {name = "default:glass"})
    -- print(dump(pos))
    -- print(endpos)

    local h_start = get_distance(pos, endpos)
    openSet[start_index] = {hCost = h_start, gCost = 0, fCost = h_start, parent = nil, pos = pos}

    -- Entity values
    local entity_height = math.ceil(entity.collisionbox[5] - entity.collisionbox[2]) or 2
    local entity_fear_height = entity.fear_height or 3
    local entity_jump_height = entity.jump_height or 1
    local neighbors_cache = {}

    repeat
        local current_index
        local current_values

        -- Get one index as reference from openSet
        for i, v in pairs(openSet) do
            current_index = i
            current_values = v
            break
        end
        -- Search for lowest fCost
        for i, v in pairs(openSet) do
            if v.fCost < openSet[current_index].fCost or v.fCost == current_values.fCost and v.hCost < current_values.hCost then
                current_index = i
                current_values = v
            end
        end

        openSet[current_index] = nil
        closedSet[current_index] = current_values
        count = count - 1

        if current_index == target_index then
            --~ minetest.chat_send_all("Found path in " .. (minetest.get_us_time() - start_time) / 1000 .. "ms")
            local path = {}
            repeat
                if not closedSet[current_index] then
                    return
                end
                table.insert(path, closedSet[current_index].pos)
                current_index = closedSet[current_index].parent
            until start_index == current_index
            table.insert(path, closedSet[current_index].pos)
            local reverse_path = {}
            repeat
                table.insert(reverse_path, table.remove(path))
            until #path == 0
            -- minetest.chat_send_all("Found path in " .. (minetest.get_us_time() - start_time) / 1000 .. "ms. " .. "Path length: " .. #reverse_path)
            return reverse_path
        end

        local current_pos = current_values.pos

        local neighbors = {}
        local neighbors_index = 1
        for z = -1, 1 do
        for x = -1, 1 do
            local neighbor_pos = {x = current_pos.x + x, y = current_pos.y, z = current_pos.z + z}
            local neighbor = minetest.get_node(neighbor_pos)
            local neighbor_ground_level = get_neighbor_ground_level(neighbor_pos, entity_jump_height, entity_fear_height, current_pos)
            local neighbor_clearance = false
            if neighbor_ground_level then
                local neighbor_hash = minetest.hash_node_position(neighbor_ground_level)
                local pos_above_head = {x = current_pos.x, y = current_pos.y + entity_height, z = current_pos.z}
                local node_above_head = minetest.get_node(pos_above_head)
                if neighbor_ground_level.y - current_pos.y > 0 and not walkable(node_above_head, pos_above_head, current_pos) then
                    local height = -1
                    repeat
                        height = height + 1
                        local pos = {   x = neighbor_ground_level.x,
                                        y = neighbor_ground_level.y + height,
                                        z = neighbor_ground_level.z}
                        local node = minetest.get_node(pos)
                    until walkable(node, pos, current_pos) or height > entity_height
                    if height >= entity_height then
                        neighbor_clearance = true
                    end
                elseif neighbor_ground_level.y - current_pos.y > 0 and walkable(node_above_head, pos_above_head, current_pos) then
                    neighbors[neighbors_index] = {
                            hash = nil,
                            pos = nil,
                            clear = nil,
                            walkable = nil,
                    }
                else
                    local height = -1
                    repeat
                        height = height + 1
                        local pos = {   x = neighbor_ground_level.x,
                                        y = current_pos.y + height,
                                        z = neighbor_ground_level.z}
                        local node = minetest.get_node(pos)
                    until walkable(node, pos, current_pos) or height > entity_height
                    if height >= entity_height then
                        neighbor_clearance = true
                    end
                end

                neighbors[neighbors_index] = {
                        hash = minetest.hash_node_position(neighbor_ground_level),
                        pos = neighbor_ground_level,
                        clear = neighbor_clearance,
                        walkable = walkable(neighbor, neighbor_pos, current_pos),
                }
            else
                neighbors[neighbors_index] = {
                        hash = nil,
                        pos = nil,
                        clear = nil,
                        walkable = nil,
                }
            end

            neighbors_index = neighbors_index + 1
        end
        end

        for id, neighbor in pairs(neighbors) do
            -- don't cut corners
            local cut_corner = false
            if id == 1 then
                if not neighbors[id + 1].clear or not neighbors[id + 3].clear
                        or neighbors[id + 1].walkable or neighbors[id + 3].walkable then
                    cut_corner = true
                end
            elseif id == 3 then
                if not neighbors[id - 1].clear or not neighbors[id + 3].clear
                        or neighbors[id - 1].walkable or neighbors[id + 3].walkable then
                    cut_corner = true
                end
            elseif id == 7 then
                if not neighbors[id + 1].clear or not neighbors[id - 3].clear
                        or neighbors[id + 1].walkable or neighbors[id - 3].walkable then
                    cut_corner = true
                end
            elseif id == 9 then
                if not neighbors[id - 1].clear or not neighbors[id - 3].clear
                        or neighbors[id - 1].walkable or neighbors[id - 3].walkable then
                    cut_corner = true
                end
            end
            if neighbor.hash ~= current_index and not closedSet[neighbor.hash] and neighbor.clear and not cut_corner then
                local move_cost_to_neighbor = current_values.gCost + get_distance_to_neighbor(current_values.pos, neighbor.pos)
                local gCost = 0
                if openSet[neighbor.hash] then
                    gCost = openSet[neighbor.hash].gCost
                end
                if move_cost_to_neighbor < gCost or not openSet[neighbor.hash] then
                    if not openSet[neighbor.hash] then
                        count = count + 1
                    end
                    local hCost = get_distance(neighbor.pos, endpos)
                    openSet[neighbor.hash] = {
                            gCost = move_cost_to_neighbor,
                            hCost = hCost,
                            fCost = move_cost_to_neighbor + hCost,
                            parent = current_index,
                            pos = neighbor.pos
                    }
                end
            end
        end
        if count > 300 then
            minetest.chat_send_all("Path fail")
            return
        end
        if (minetest.get_us_time() - start_time) / 1000 > 30 - dtime * 50 then
            -- 231111 RJK: Suppress a debug message
            -- minetest.chat_send_all ("Path timeout")
            return
        end
    until count < 1

-- 220502 RJK: Suppress a debug message
--  minetest.chat_send_all("count < 1")

    return {pos}
end