local ui = {}

ui.theme = {
    bg          = {0.13, 0.13, 0.14},
    panel       = {0.17, 0.17, 0.19},
    border      = {0.28, 0.28, 0.30},
    borderwidth = 3,
    text        = {0.90, 0.90, 0.90},
    text_dim    = {0.50, 0.50, 0.55},
    accent      = {0.27, 0.52, 0.90},
    hover       = {0.22, 0.25, 0.35},
    active      = {0.20, 0.40, 0.75},
}

ui.theme2 = {
    bg          = {0.5, 0, 0},
    panel       = {0.25, 0, 0},
    border      = {1, 0, 0},
    borderwidth = 3,
    text        = {0, 0, 1},
    text_dim    = {1, 0, 0},
    accent      = {0.7, 0, 0},
    hover       = {1, 0, 0},
    active      = {1, 0, 0},
}

ui.activeTheme = ui.theme

-- per-frame state (most/all gets reset if i remember)
ui._wasDown       = false
ui._focused       = nil
ui._inputs        = {}
ui._claimedFocus  = false
ui._clickConsumed = false
ui._elements      = {} -- queue of UI elements, processed at end of frame
ui._hoverConsumed = false -- so it sets hovered to the correct thing

-- draws a basic bordered panel
function ui._draw_panel(e)
    love.graphics.setColor(ui.activeTheme.panel)
    love.graphics.rectangle("fill", e.x, e.y, e.w, e.h)
    love.graphics.setColor(ui.activeTheme.border)
    love.graphics.setLineWidth(ui.activeTheme.borderwidth)
    love.graphics.rectangle("line", e.x, e.y, e.w, e.h)
end

-- draws centered, wrapped, clipped text inside a box
function ui._draw_text(e)
    local font = love.graphics.getFont()
    local _, lines = font:getWrap(e.text, e.w)
    local totalHeight = #lines * font:getHeight()
    local startY = e.y + (e.h - totalHeight) / 2

    love.graphics.setScissor(e.x, e.y, e.w, e.h) -- clip to box bounds
    love.graphics.setColor(ui.activeTheme.text)
    love.graphics.printf(e.text, e.x, startY, e.w, "center")
    love.graphics.setScissor() -- reset clip
end

-- draws a button, highlighted on hover
function ui._draw_button(e)
    local mx, my = love.mouse.getPosition()
    local hovered = not ui._hoverConsumed and mx > e.x and mx < e.x + e.w and my > e.y and my < e.y + e.h

    love.graphics.setColor(e._hovered and ui.activeTheme.hover or ui.activeTheme.panel)
    love.graphics.rectangle("fill", e.x, e.y, e.w, e.h)
    love.graphics.setColor(ui.activeTheme.border)
    love.graphics.setLineWidth(ui.activeTheme.borderwidth)
    love.graphics.rectangle("line", e.x, e.y, e.w, e.h)
    ui._draw_text(e)
end

-- draws a text input, changes appearance based on focus state
function ui._draw_textInput(e)
    local focused = ui._focused == e.placeholder
    local text    = ui._inputs[e.placeholder] or ""

    if focused then
        love.graphics.setColor(ui.activeTheme.panel)
        love.graphics.rectangle("fill", e.x, e.y, e.w, e.h)
        love.graphics.setColor(ui.activeTheme.accent)
        love.graphics.setLineWidth(ui.activeTheme.borderwidth)
        love.graphics.rectangle("line", e.x, e.y, e.w, e.h)

        if text == "" then
            -- show dimmed placeholder text when empty
            local font = love.graphics.getFont()
            local startY = e.y + (e.h - font:getHeight()) / 2
            love.graphics.setColor(ui.activeTheme.text_dim)
            love.graphics.printf(e.placeholder, e.x + 4, startY, e.w - 8, "left")
        else
            ui._draw_text({ x=e.x, y=e.y, w=e.w, h=e.h, text=text })
        end
    else
        -- unfocused
        local display = text == "" and e.placeholder or text
        ui._draw_button({ x=e.x, y=e.y, w=e.w, h=e.h, text=display })
    end
end

-- bordered panel, no interaction
function ui.panel(x, y, w, h)
    table.insert(ui._elements, {
        type = "panel",
        x=x, y=y, w=w, h=h
    })
end

-- centered text inside a box, no background
function ui.text(x, y, w, h, text)
    table.insert(ui._elements, {
        type = "text",
        x=x, y=y, w=w, h=h, text=text
    })
end

-- panel with centered text inside (justs draws a panel and puts text ontop, dependant on ui.text)
function ui.textPanel(x, y, w, h, text)
    table.insert(ui._elements, {
        type = "textPanel",
        x=x, y=y, w=w, h=h, text=text
    })
end

-- clickable button. callback is called when clicked (optional)
-- example: ui.button(x, y, w, h, "Click me", function() print("hi") end)
function ui.button(x, y, w, h, text, callback)
    table.insert(ui._elements, {
        type = "button",
        x=x, y=y, w=w, h=h, text=text,
        callback = callback
    })
end

-- text input field. placeholder is also used as its unique ID
-- read typed text with: ui._inputs["placeholder"]
function ui.textInput(x, y, w, h, placeholder)
    table.insert(ui._elements, {
        type = "textInput",
        x=x, y=y, w=w, h=h,
        placeholder = placeholder
    })
end

function ui.process()
    local mx, my   = love.mouse.getPosition()
    local clicked   = love.mouse.isDown(1) and not ui._wasDown
    for i = #ui._elements, 1, -1 do
        local e = ui._elements[i]
        local inside = mx > e.x and mx < e.x + e.w and my > e.y and my < e.y + e.h

        -- consume hover for top thing
        if inside and not ui._hoverConsumed then
            e._hovered = true
            ui._hoverConsumed = true
        else
            e._hovered = false
        end
    end

    -- reverse hit test so topmost element gets the click, similar to above but just for clicking
    for i = #ui._elements, 1, -1 do
        local e = ui._elements[i]
        if clicked and not ui._clickConsumed then
            local inside = mx > e.x and mx < e.x + e.w and my > e.y and my < e.y + e.h
            if inside then
                if e.type == "button" then
                    if e.callback then e.callback() end -- fire callback if provided
                    ui._clickConsumed = true

                elseif e.type == "textInput" then
                    ui._focused      = e.placeholder
                    ui._claimedFocus = true
                    ui._clickConsumed = true
                end
            end
        end
    end

    -- clicked outside everything, clear focus
    if clicked and not ui._claimedFocus then
        ui._focused = nil
    end

    -- draw in order
    for i = 1, #ui._elements do
        local e = ui._elements[i]
        if     e.type == "panel"     then ui._draw_panel(e)
        elseif e.type == "text"      then ui._draw_text(e)
        elseif e.type == "textPanel" then ui._draw_panel(e) ui._draw_text(e)
        elseif e.type == "button"    then ui._draw_button(e)
        elseif e.type == "textInput" then ui._draw_textInput(e)
        end
    end

    -- clear queue/list for next frame (leave at end)
    ui._elements = {}
end

function ui.flush()
    ui._wasDown       = love.mouse.isDown(1)
    ui._claimedFocus  = false
    ui._clickConsumed = false
    ui._hoverConsumed = false
end

-- text things, both used in the process of rendering text
function ui.textinput_char(t)
    if ui._focused then
        ui._inputs[ui._focused] = (ui._inputs[ui._focused] or "") .. t
    end
end

function ui.textinput_backspace()
    if ui._focused then
        local str = ui._inputs[ui._focused] or ""
        ui._inputs[ui._focused] = str:sub(1, -2)
    end
end

return ui