-- A modified version of the final code block licensed under the MIT from this blog post: https://fredchan.org/blog/vein-mining-strategies-with-computercraft-2/

--- Calculate the destination coordinate from current pos, orientation, and desired turn
-- This calculation is RELATIVE and doesn't correspond with Minecraft's F3 coordinates
-- @param Table xyz             Table of coordinates {x,y,z} of the starting point
-- @param String orientation    The cardinal direction you face at the starting point
-- @param String direction      The direction (e.g. left, right, up) you would turn and proceed into
-- @return { {x, y, z}, orientation } of destination
function calcDest (xyz, orientation, direction)
    local dest = {x=xyz['x'], y=xyz['y'], z=xyz['z']}
    if direction == 'up' then
        dest['y'] = dest['y'] + 1
    elseif direction == 'down' then
        dest['y'] = dest['y'] - 1
    else
        local cardinals = {north=0, west=1, south=2, east=3}
        local cardinalsReverse = {[0]='north', 'west', 'south', 'east'}
        local leftTurns = {front=0, left=1, back=2, right=3}
        orientation = cardinalsReverse[(cardinals[orientation] + leftTurns[direction]) % 4]
        if orientation == 'north' then
            dest['z'] = dest['z'] + 1
        elseif orientation == 'south' then
            dest['z'] = dest['z'] - 1
        elseif orientation == 'east' then
            dest['x'] = dest['x'] + 1
        elseif orientation == 'west' then
            dest['x'] = dest['x'] - 1
        end
    end
    return {dest, orientation}
end

--- Test if a table of {x,y,z}s contains a certain {x,y,z}
-- @param Table table   table to search within
-- @param Table xyz     xyz to search for
-- @return Boolean of whether the table has the xyz
function contains (table, xyz)
    for _,v in ipairs(table) do 
        if v['x'] == xyz['x'] and v['y'] == xyz['y'] and v['z'] == xyz['z'] then
            return true
        end
    end
    return false
end

--- Master function for mining a vein of treasures as if it were a graph
-- with each block as a node and the directions you can travel from that block as edges
-- When beginning to mine, assumes whatever orientation the turtle is facing as "north"
-- and wherever it started mining as {0, 0, 0} xyz
-- @param Function isTreasure   Given a block's data, returns true if it's a treasure
local function mineVein (isTreasure)
    mineVeinHelper({x=0, y=0, z=0}, 'north', {}, isTreasure)
end

--- Recursive helper function for mining a vein of treasures (blocks)
-- using the graph traversal method
-- @param Table xyz             Current location {x,y,z} of turtle
-- @param String orientation    Current orientation of turtle
-- @param Table traversed       Table of tables {x,y,z} of visited blocks
-- @param Function isTreasure   Given a block's data, returns true if it's a treasure
function mineVeinHelper (xyz, orientation, traversed, isTreasure)
    for _, direction in ipairs({'up', 'down', 'front', 'back', 'left', 'right'}) do
        local destination, newOrientation = table.unpack(calcDest(xyz, orientation, direction))
        if not contains(traversed, destination) then
            if direction ~= 'back' then
                table.insert(traversed, destination)
            end

            if direction == 'up' then
                local success, data = turtle.inspectUp()
                if success and isTreasure(data) then
                    turtle.digUp()
                    turtle.up()
                    mineVeinHelper(destination, newOrientation, traversed, isTreasure);
                    turtle.down()
                end
            elseif direction == 'down' then
                local success, data = turtle.inspectDown()
                if success and isTreasure(data) then
                    turtle.digDown()
                    turtle.down()
                    mineVeinHelper(destination, newOrientation, traversed, isTreasure);
                    turtle.up()
                end
            elseif direction == 'back' then
                local leftOrient = orientation
                for i=1, 3 do
                    local calculated = calcDest(xyz, leftOrient, 'left')
                    local leftDest = calculated[1]
                    leftOrient = calculated[2]
                    turtle.turnLeft()
                    table.insert(traversed, leftDest)
                    local success, data = turtle.inspect()
                    if success and isTreasure(data) then
                        turtle.dig()
                        turtle.forward()
                        mineVeinHelper(leftDest, leftOrient, traversed, isTreasure);
                        turtle.back()
                    end
                end
                turtle.turnLeft()
            else
                --turn in the direction to inspect
                if direction == 'left' then turtle.turnLeft()
                elseif direction == 'right' then turtle.turnRight()
                end
                --inspect the block
                local success, data = turtle.inspect()
                if success and isTreasure(data) then
                    turtle.dig()
                    turtle.forward()
                    mineVeinHelper(destination, newOrientation, traversed, isTreasure);
                    turtle.back()
                end
                --unturn to face forwards again
                if direction == 'left' then turtle.turnRight()
                elseif direction == 'right' then turtle.turnLeft()
                end
            end
        end
    end
end

return mineVein