oma-tank/game/horizon.lua

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

local Horizon = {}

-- Mountain profile: angular peaks as straight line segments
-- Each entry is {angle_degrees, height} — connected by straight lines
local mountainPoints = {}
local smokeParticles = {}
local VOLCANO_ANGLE = 230
-- Eruption phase: alternates between "quiet" and "active" periods so smoke reads as an eruption cycle
local eruption = { active = false, timer = 0, nextCycle = 8 }

-- Deterministic small PRNG for the mountain profile so the horizon stays the
-- same across a single session without touching math.random's global state.
local function lcg(seed)
    local state = seed
    return function()
        state = (state * 1103515245 + 12345) % 2147483648
        return state / 2147483648
    end
end

function Horizon.init()
    mountainPoints = {}

    local rnd = lcg(12345)
    local angle = 0
    while angle < 360 do
        local h = rnd() < 0.45
            and (25 + rnd() * 45)       -- peak
            or (2 + rnd() * 10)         -- valley / flat
        table.insert(mountainPoints, {angle = angle, height = h})
        -- Variable spacing — bigger jumps for angular look
        angle = angle + 4 + rnd() * 8
    end
    -- Close the loop
    table.insert(mountainPoints, {angle = 360, height = mountainPoints[1].height})

    -- Tall narrow volcano
    local volcanoPts = {
        {VOLCANO_ANGLE - 15, 8},
        {VOLCANO_ANGLE - 8, 25},
        {VOLCANO_ANGLE - 3, 55},
        {VOLCANO_ANGLE, 75},
        {VOLCANO_ANGLE + 3, 55},
        {VOLCANO_ANGLE + 8, 25},
        {VOLCANO_ANGLE + 15, 8},
    }
    for _, vp in ipairs(volcanoPts) do
        table.insert(mountainPoints, {angle = vp[1], height = vp[2]})
    end

    table.sort(mountainPoints, function(a, b) return a.angle < b.angle end)

    smokeParticles = {}
    eruption.active = false
    eruption.timer = 0
    eruption.nextCycle = 8 + math.random() * 6
end

-- Get mountain height at a specific angle by interpolating between nearest points
local function getMountainHeight(deg)
    deg = deg % 360
    -- Find the two points bracketing this angle
    local prev = mountainPoints[#mountainPoints - 1]
    local nxt = mountainPoints[1]

    for i = 1, #mountainPoints - 1 do
        if mountainPoints[i].angle <= deg and mountainPoints[i + 1].angle > deg then
            prev = mountainPoints[i]
            nxt = mountainPoints[i + 1]
            break
        end
    end

    -- Linear interpolation between the two points
    local range = nxt.angle - prev.angle
    if range <= 0 then return prev.height end
    local t = (deg - prev.angle) / range
    return prev.height + (nxt.height - prev.height) * t
end

function Horizon.update(dt)
    -- Eruption cycle: quiet stretches then 3-5s active bursts
    eruption.timer = eruption.timer + dt
    if eruption.timer >= eruption.nextCycle then
        eruption.timer = 0
        eruption.active = not eruption.active
        eruption.nextCycle = eruption.active
            and (3 + math.random() * 2)       -- active burst duration
            or (10 + math.random() * 10)      -- quiet interval between eruptions
    end

    if eruption.active and math.random() < 0.5 then
        table.insert(smokeParticles, {
            angle = VOLCANO_ANGLE + (math.random() - 0.5) * 6,
            height = 78 + math.random() * 5,
            vy = 18 + math.random() * 14,
            vangle = (math.random() - 0.5) * 1.5,
            life = 2.0 + math.random(),
            maxLife = 3.0,
            size = 1 + math.random() * 1.5,
        })
    end
    for i = #smokeParticles, 1, -1 do
        local sp = smokeParticles[i]
        sp.height = sp.height + sp.vy * dt
        sp.angle = sp.angle + sp.vangle * dt
        sp.life = sp.life - dt
        if sp.life <= 0 then table.remove(smokeParticles, i) end
    end
end

function Horizon.draw(cameraAngle)
    local p = Palette.get()
    local vp = Projection.getViewport()
    -- Procedural horizon "distance": smaller divisor → mountains appear closer/bigger.
    -- 700 gives mountains roughly double the apparent size of our previous 1500 value
    -- so the horizon reads as a near-ish backdrop rather than vanishingly far away.
    local FAR_SCALE = (vp.w / 2 * math.sqrt(3)) / 700

    -- === STRONG HORIZON LINE ===
    love.graphics.setColor(p.fg[1], p.fg[2], p.fg[3], 0.8)
    love.graphics.setLineWidth(2)
    love.graphics.line(vp.x, vp.horizonY, vp.x + vp.w, vp.horizonY)

    -- === MOUNTAINS: angular connected peaks ===
    love.graphics.setColor(p.fg[1], p.fg[2], p.fg[3], 0.7)
    love.graphics.setLineWidth(1.5)

    -- Walk across screen columns in larger steps for angular look
    local pts = {}
    local step = 3
    for sx = vp.x, vp.x + vp.w, step do
        local relX = (sx - vp.x - vp.w / 2) / (vp.w / 2)
        local worldAngle = cameraAngle + math.atan(relX)
        local deg = math.deg(worldAngle) % 360

        local height = getMountainHeight(deg)
        local sy = vp.horizonY - height * FAR_SCALE

        table.insert(pts, sx)
        table.insert(pts, sy)
    end

    if #pts >= 4 then
        love.graphics.line(pts)
    end

    -- === MOON ===
    local moonWorldAngle = math.rad(10)
    local moonRelAngle = moonWorldAngle - cameraAngle
    while moonRelAngle > math.pi do moonRelAngle = moonRelAngle - math.pi * 2 end
    while moonRelAngle < -math.pi do moonRelAngle = moonRelAngle + math.pi * 2 end

    if math.abs(moonRelAngle) < math.pi / 4 then
        local moonSx = vp.x + vp.w/2 + math.tan(moonRelAngle) * (vp.w/2)
        local moonSy = vp.horizonY - vp.h * 0.28
        local moonR = vp.h * 0.035

        love.graphics.setColor(p.fg[1], p.fg[2], p.fg[3], 0.5)
        love.graphics.setLineWidth(1.5)
        love.graphics.circle("line", moonSx, moonSy, moonR, 16)
        -- Crescent shadow
        love.graphics.setColor(p.fg[1], p.fg[2], p.fg[3], 0.2)
        love.graphics.arc("line", "open", moonSx + moonR*0.3, moonSy, moonR*0.7, -math.pi/2, math.pi/2, 10)
    end

    -- === VOLCANO SMOKE ===
    for _, sp in ipairs(smokeParticles) do
        local spRel = math.rad(sp.angle) - cameraAngle
        while spRel > math.pi do spRel = spRel - math.pi * 2 end
        while spRel < -math.pi do spRel = spRel + math.pi * 2 end

        if math.abs(spRel) < math.pi / 4 then
            local spSx = vp.x + vp.w/2 + math.tan(spRel) * (vp.w/2)
            local spSy = vp.horizonY - sp.height * FAR_SCALE
            local alpha = 0.35 * (sp.life / sp.maxLife)
            love.graphics.setColor(p.fg[1], p.fg[2], p.fg[3], alpha)
            love.graphics.circle("fill", spSx, spSy, sp.size)
        end
    end
end

return Horizon