--[[--
A text entry area.

@widget text
--]]--
local ROOT = (...):gsub('[^.]*.[^.]*$', '')

local utf8 = require(ROOT .. 'utf8')
local Backend = require(ROOT .. 'backend')

-- make sure selection range doesn't extend past EOT
local function trimRange (self)
    local max = #self.value
    if self.startIndex > max then self.startIndex = max end
    if self.endIndex > max then self.endIndex = max end
end

local function updateHighlight (self)
    local value = self.value
    local font = self:getFont()
    local startIndex, endIndex = self.startIndex, self.endIndex
    local offset = self:getRectangle(true, true) - self.scrollX
    self.startX = font:getAdvance(value:sub(1, startIndex)) + offset
    self.endX = font:getAdvance(value:sub(1, endIndex)) + offset
end

local function scrollToCaret (self)
    updateHighlight(self)
    local x1, y1, w, h = self:getRectangle(true, true)
    local x2, y2 = x1 + w, y1 + h
    local oldX = self.endX or x1

    if oldX <= x1 then
        self.scrollX = self.scrollX - (x1 - oldX)
        updateHighlight(self)
    elseif oldX >= x2 then
        self.scrollX = self.scrollX + (oldX - x2 + 1)
        updateHighlight(self)
    end
end

local function selectRange (self, startIndex, endIndex)
    if startIndex then self.startIndex = startIndex end
    if endIndex then self.endIndex = endIndex end
    trimRange(self)

    scrollToCaret(self)
end

-- return caret index
local function findIndexFromPoint (self, x, y)
    local x1 = self:getRectangle(true, true)

    local font = self.fontData
    local width = 0
    local lastPosition = 0

    local function checkPosition (position)
        local text = self.value:sub(1, position - 1)
        width = font:getAdvance(text)
        if width > x + self.scrollX - x1 then
            if position == 1 then
                return 0
            end
            return lastPosition
        end
        lastPosition = position - 1
    end

    for position in utf8.codes(self.value) do
        local index = checkPosition(position)
        if index then return index end
    end

    local index = checkPosition(#self.value + 1)
    if index then return index end

    return #self.value
end

-- move the caret or end of selection range one character to the left
local function moveCharLeft (self, alterRange)
    trimRange(self)
    local text, endIndex = self.value, self.endIndex

    -- clamp caret to beginning
    if endIndex < 1 then endIndex = 1 end

    -- move left
    local index = (utf8.offset(text, -1, endIndex + 1) or 0) - 1
    selectRange(self, not alterRange and index, index)
end

-- move caret or end of selection range one word to the left
local function moveWordLeft (self, alterRange)
    trimRange(self)
    local text = self.value:sub(1, self.endIndex)
    local pos = text:find('%s[^%s]+%s*$') or 0
    selectRange(self, not alterRange and pos, pos)
end

-- move the caret or end of selection range to the beginning of the line
local function moveLineLeft (self, alterRange)
    trimRange(self)
    selectRange(self, not alterRange and 0, 0)
end

-- move caret or end of selection range one character to the right
local function moveCharRight (self, alterRange)
    trimRange(self)
    local text, endIndex = self.value, self.endIndex

    -- clamp caret to end
    if endIndex >= #text then endIndex = #text - 1 end

    -- move right
    local index = (utf8.offset(text, 2, endIndex + 1) or #text) - 1
    selectRange(self, not alterRange and index, index)
end

-- move caret or end of selection range one word to the right
local function moveWordRight (self, alterRange)
    trimRange(self)
    local text = self.value
    local _, pos = text:find('^%s*[^%s]+', self.endIndex + 1)
    pos = pos or #text + 1
    selectRange(self, not alterRange and pos, pos)
end

-- move caret or end of selection range to the end of the line
local function moveLineRight (self, alterRange)
    trimRange(self)
    local text = self.value
    selectRange(self, not alterRange and #text, #text)
end

local function getRange (self)
    trimRange(self)
    if self.startIndex <= self.endIndex then
        return self.startIndex, self.endIndex
    end

    return self.endIndex, self.startIndex
end

local function deleteRange (self)
    trimRange(self)
    local text = self.value
    local first, last = getRange(self)

    -- if expanded range is selected, delete text in range
    if first ~= last then
        local left = text:sub(1, first)
        local index = #left
        self.value = left .. text:sub(last + 1)
        selectRange(self, index, index)
        return true
    end
end

local function deleteCharacterLeft (self)
    trimRange(self)
    local text = self.value
    local first, last = getRange(self)

    -- if cursor is at beginning, do nothing
    if first < 1 then
        return
    end

    -- delete character to the left
    local offset = utf8.offset(text, -1, last + 1) or 0
    local left = text:sub(1, offset - 1)
    local index = #left
    self.value = left .. text:sub(first + 1)
    selectRange(self, index, index)
end

local function deleteCharacterRight (self)
    trimRange(self)
    local text = self.value
    local first, last = getRange(self)

    -- if cursor is at end, do nothing
    if first == #text then
        return
    end

    -- delete character to the right
    local offset = utf8.offset(text, 2, last + 1) or 0
    local left = text:sub(1, first)
    local index = #left
    self.value = left .. text:sub(offset)
    selectRange(self, index, index)
end

local function copyRangeToClipboard (self)
    trimRange(self)
    local text = self.value
    local first, last = getRange(self)
    if last >= first + 1 then
        Backend.setClipboardText(text:sub(first + 1, last))
    end
end

local function pasteFromClipboard (self)
    trimRange(self)
    local text = self.value
    local pasted = Backend.getClipboardText() or ''
    local first, last = getRange(self)
    local left = text:sub(1, first) .. pasted
    local index = #left
    self.value = left .. text:sub(last + 1)
    selectRange(self, index, index)
end

local function insertText (self, newText)
    trimRange(self)
    local text = self.value
    local first, last = getRange(self)
    local left = text:sub(1, first) .. newText
    local index = #left
    self.value = left .. text:sub(last + 1)
    selectRange(self, index, index)
end

local function isShiftPressed ()
    return Backend.isKeyDown('lshift', 'rshift')
end

-- check command (gui) key, only on Mac.
local isCommandPressed
if Backend.isMac() then
    isCommandPressed = function ()
        return Backend.isKeyDown('lgui', 'rgui')
    end
else
    isCommandPressed = function ()
        return false
    end
end

-- check command (gui) key on Mac and ctrl key everywhere else.
local isCommandOrCtrlPressed
if Backend.isMac() then
    isCommandOrCtrlPressed = function ()
        return Backend.isKeyDown('lgui', 'rgui')
    end
else
    isCommandOrCtrlPressed = function ()
        return Backend.isKeyDown('lctrl', 'rctrl')
    end
end

-- check option (alt) key on Mac and ctrl key everywhere else.
local isOptionOrCtrlPressed
if Backend.isMac() then
    isOptionOrCtrlPressed = function ()
        return Backend.isKeyDown('lalt', 'ralt')
    end
else
    isOptionOrCtrlPressed = function ()
        return Backend.isKeyDown('lctrl', 'rctrl')
    end
end

-- Special keys.
local function createDefaultKeyActions (self)
    return {
        -- let tab press propagate
        ['tab'] = function () return true end,
        ['backspace'] = function ()
            if not deleteRange(self) then
                deleteCharacterLeft(self)
            end
        end,
        ['delete'] = function ()
            if not deleteRange(self) then
                deleteCharacterRight(self)
            end
        end,
        ['left'] = function ()
            if isOptionOrCtrlPressed() then
                moveWordLeft(self, isShiftPressed())
            elseif isCommandPressed() then
                moveLineLeft(self, isShiftPressed())
            else
                moveCharLeft(self, isShiftPressed())
            end
        end,
        ['right'] = function ()
            if isOptionOrCtrlPressed() then
                moveWordRight(self, isShiftPressed())
            elseif isCommandPressed() then
                moveLineRight(self, isShiftPressed())
            else
                moveCharRight(self, isShiftPressed())
            end
        end,
        ['home'] = function ()
            moveLineLeft(self, isShiftPressed())
        end,
        ['end'] = function ()
            moveLineRight(self, isShiftPressed())
        end,
        ['x'] = function ()
            if isCommandOrCtrlPressed() then
                copyRangeToClipboard(self)
                deleteRange(self)
            end
        end,
        ['c'] = function ()
            if isCommandOrCtrlPressed() then
                copyRangeToClipboard(self)
            end
        end,
        ['v'] = function ()
            if isCommandOrCtrlPressed() then
                pasteFromClipboard(self)
            end
        end,
        ['a'] = function ()
            if isCommandOrCtrlPressed() then
                selectRange(self, 0, #self.value)
            end
        end,
    }
end

local textInputKeys = {
    ['space'] = true,
    ['return'] = true,
    ['kp00'] = true,
    ['kp000'] = true,
    ['kp&&'] = true,
    ['kp||'] = true,
}

local function isKeyTextInput (key)
    if textInputKeys[key] or #key == 1
    or (#key == 3 and key:sub(1, 2) == "kp") then
        return not Backend.isKeyDown(
            'lalt', 'ralt', 'lctrl', 'rctrl', 'lgui', 'rgui')
    end
    return false
end

return function (self)
    self.startIndex, self.endIndex = 0, 0
    self.startX, self.endX = -1, -1
    self.scrollX = 0
    self.value = tostring(self.value or self.text or '')
    self.text = ''
    self.keyActions = createDefaultKeyActions(self)

--[[--
Special Attributes

@section special
--]]--

--[[--
Highlight color.

Should contain an array with 3 or 4 values (RGB or RGBA) from 0 to 255.

This color is used to indicate the selected range of text.

@attrib highlight
--]]--

    self:defineAttribute('highlight')
    local defaultHighlight = { 0x80, 0x80, 0x80, 0x80 }
--[[--
@section end
--]]--

    self:onPressStart(function (event)
        if event.button ~= 'left' then return end
        self.startIndex = findIndexFromPoint(self, event.x)
        self.endIndex = self.startIndex
        scrollToCaret(self)
    end)

    self:onPressDrag(function (event)
        if event.button ~= 'left' then return end
        self.endIndex = findIndexFromPoint(self, event.x)
        scrollToCaret(self)
    end)

    self:onTextInput(function (event)
        insertText(self, event.text)
    end)

    self:onKeyPress(function (event)
        local key = event.key
        local act = self.keyActions[key]
        if act then
            if act() then return end
        end
        return isKeyTextInput(key) or nil
    end)

    self:onDisplay(function (event)
        local startX, endX = self.startX, self.endX
        local x, y, w, h = self:getRectangle(true, true)
        local width, height = endX - startX, h
        local font = self:getFont()
        local color = self.color or { 0, 0, 0, 255 }
        local textTop = math.floor(y + (h - font:getLineHeight()) / 2)

        Backend.push()
        Backend.intersectScissor(x, y, w, h)
        Backend.setFont(font)

        if self.focused then
            -- draw highlighted selection
            Backend.setColor(self.highlight or defaultHighlight)
            Backend.drawRectangle('fill', startX, y, width, height)
            -- draw cursor selection
            if Backend.getTime() % 2 < 1.75 then
                Backend.setColor(color)
                Backend.drawRectangle('fill', endX, y, 1, height)
            end
        else
            Backend.setColor { color[1], color[2], color[3],
                (color[4] or 256) / 8 }
            Backend.drawRectangle('fill', startX, y, width, height)
        end

        -- draw text
        Backend.setColor(color)
        Backend.print(self.value, x - self.scrollX, textTop)

        Backend.pop()
    end)

    self:onReshape(function ()
        updateHighlight(self)
    end)
end