local World = require("game.world")
local Palette = require("rendering.palette")

local Terrain = {}

local points = {}
local pads = {}

function Terrain.generate()
    points = {}
    pads = {}

    local W = World.WORLD_W
    local baseline = 1600
    local step = 30

    -- Place landing pads first
    local padDefs = {
        {width = 120, mult = 2, label = "2X"},
        {width = 80,  mult = 3, label = "3X"},
        {width = 50,  mult = 5, label = "5X"},
    }

    -- Distribute pads across the terrain
    local padPositions = {}
    local usedZones = {}
    for _, def in ipairs(padDefs) do
        local attempts = 0
        local px
        repeat
            px = 400 + math.random() * (W - 800)
            attempts = attempts + 1
            local ok = true
            for _, used in ipairs(usedZones) do
                if math.abs(px - used) < 400 then ok = false; break end
            end
            if ok then break end
        until attempts > 50

        local py = baseline + (math.random() - 0.5) * 200
        table.insert(padPositions, {x = px, y = py, width = def.width, mult = def.mult, label = def.label})
        table.insert(usedZones, px)
        table.insert(pads, {
            x1 = px - def.width / 2,
            x2 = px + def.width / 2,
            y = py,
            mult = def.mult,
            label = def.label,
        })
    end

    -- Sort pads by X for terrain generation
    table.sort(pads, function(a, b) return a.x1 < b.x1 end)

    -- Generate terrain points left to right
    local x = 0
    local y = baseline + (math.random() - 0.5) * 100
    table.insert(points, {x = x, y = y})

    while x < W do
        -- Check if we're approaching a pad
        local onPad = false
        local currentPad = nil
        for _, pad in ipairs(pads) do
            if x >= pad.x1 - step and x <= pad.x2 + step then
                onPad = true
                currentPad = pad
                break
            end
        end

        if onPad and currentPad then
            -- Transition to pad level
            if x < currentPad.x1 then
                -- Approach: slope down/up to pad
                table.insert(points, {x = currentPad.x1 - 5, y = y})
                table.insert(points, {x = currentPad.x1, y = currentPad.y})
                x = currentPad.x1
            end
            -- Flat pad
            table.insert(points, {x = currentPad.x2, y = currentPad.y})
            x = currentPad.x2
            y = currentPad.y
            -- Resume jagged after pad
            x = x + step * 0.5
            y = y + (math.random() - 0.5) * 60
            table.insert(points, {x = x, y = y})
        else
            x = x + step + math.random() * step
            -- Jagged variation
            y = y + (math.random() - 0.5) * 120
            y = math.max(baseline - 250, math.min(baseline + 250, y))
            table.insert(points, {x = x, y = y})
        end
    end

    -- Ensure last point reaches edge
    table.insert(points, {x = W, y = points[#points].y})
end

function Terrain.getPoints()
    return points
end

function Terrain.getPads()
    return pads
end

function Terrain.getHeightAt(wx)
    -- Find terrain height at world X by interpolating between points
    if #points < 2 then return 1600 end
    if wx <= points[1].x then return points[1].y end
    if wx >= points[#points].x then return points[#points].y end

    for i = 1, #points - 1 do
        if points[i].x <= wx and points[i+1].x > wx then
            local t = (wx - points[i].x) / (points[i+1].x - points[i].x)
            return points[i].y + t * (points[i+1].y - points[i].y)
        end
    end
    return 1600
end

function Terrain.getPadAt(wx)
    for _, pad in ipairs(pads) do
        if wx >= pad.x1 and wx <= pad.x2 then
            return pad
        end
    end
    return nil
end

function Terrain.draw(visMinX, visMaxX)
    local p = Palette.get()

    -- Draw terrain surface
    love.graphics.setColor(p.terrain)
    love.graphics.setLineWidth(2)

    local pts = {}
    for _, pt in ipairs(points) do
        if pt.x >= visMinX - 100 and pt.x <= visMaxX + 100 then
            table.insert(pts, pt.x)
            table.insert(pts, pt.y)
        end
    end
    if #pts >= 4 then
        love.graphics.line(pts)
    end

    -- Draw landing pads (brighter, with labels)
    love.graphics.setColor(p.pad)
    love.graphics.setLineWidth(3)
    for _, pad in ipairs(pads) do
        if pad.x2 >= visMinX and pad.x1 <= visMaxX then
            love.graphics.line(pad.x1, pad.y, pad.x2, pad.y)

            -- Label below pad
            love.graphics.setColor(p.pad[1], p.pad[2], p.pad[3], 0.7)
            local labelX = (pad.x1 + pad.x2) / 2
            love.graphics.print(pad.label, labelX - 8, pad.y + 5)
        end
    end
end

return Terrain