Pathfinding on Netlogo - Robotic lawn mower simulation project - netlogo

Question

I am trying to simulate a robotic lawn mower on Netlogo. My goals were that :
It goes randomly on green patches (grass) to cut them (green turns grey).
It finds its way home to recharge itself when the battery is low.
It does not go away the defined perimeter (garden) narrowed by red patches and goes arround obstacles placed by user with mouse clicks.
I have now a working code for my two first objectives(thanks to Luke !).
However making the lawn mower respect my whish of not going on red patches is getting complicated after getting in the to check death step.
Indeed it seems that it does not take into account my previous orders in the to move-cars step.
Some people told me that if I wanted to make it navigate around the walls it would be actually pretty involved and will require some kind of pathfinding.
Through my research I found some documentation about what is called an A*.
I understood the concept of the algorithm well but its translation on Netlogo is very difficult for me. What I did without a course so far was pretty basic, based on existing codes and following the advice I was given. But from now on, adapting an A* for my code makes me lose my hair. I hope to be able to finally understand the intricacies of Netlogo by understanding how pathfinding would be implemented in my code.
I understand that some people will not want to dwell on explaining how it works. I just hope to find someone patient enough to explain to me how things work with an A* step by step.
Thanks a lot
Here's my code :
breed [cars car]
cars-own [target charging? charge-time car-energy]
breed [houses house]
to setup
clear-all
setup-patches
setup-cars
setup-house
reset-ticks
end
to setup-patches
ask patches [set pcolor green] ;; Setup grass patches
ask patches with [
pxcor = max-pxcor or
pxcor = min-pxcor or
pycor = max-pycor or
pycor = min-pycor ] [
set pcolor red ;; Setup garden perimeter
]
end
to setup-cars
set-default-shape cars "car"
create-cars 1 [
setxy 8 8 ;; Place the lawn mower near the house
set target one-of houses
set charging? false
set car-energy energy
]
end
to setup-house
set-default-shape houses "house"
ask patch 7 8 [sprout-houses 1]
end
to place-walls
if mouse-down? [
ask patch mouse-xcor mouse-ycor [ set pcolor red ]
display ;; Permits the user to place red patches as new obstacles in garden.
]
end
to go
move-cars
cut-grass
check-death ;; Verify % battery.
tick
end
to move-cars
ask cars [
ifelse charging? [
set charge-time charge-time + 1 ;; Counts the time spent to charge
if charge-time > 15 [ ;; Defined charge time here
set car-energy 1000
set charging? false
set charge-time 0
]
] [
ifelse [pcolor] of patch-ahead 1 = red
[ lt random-float 360 ] ;; See a red patch ahead : turn left randomly
[ fd 1 ] ;; Otherwise, its safe to go foward.
set car-energy car-energy - 1
]
]
end
to cut-grass
ask cars [
if pcolor = green [ ;; cut grass (green patches go grey)
set pcolor gray
]
]
end
to check-death ;; checking battery level
ask cars [
ifelse car-energy >= 300
[ set label "Energy ok" ]
[ set label "Low Energy, returning to base"
set target min-one-of houses [distance myself]
face target
ifelse distance target < 1
[ move-to target
set charging? true
set label "Charging"
]
[ fd 1 ]
]
]
end