--:Minify:--
--   Arrows          move cursor       Home/End        line start/end
--   PgUp/PgDn       page up/down      Backspace       delete left
--   Ctrl-D/Delete   delete right      Tab             4 spaces
--   Ctrl-W          save              Ctrl-X          save + quit
--   Ctrl-P          quit              Ctrl-K          cut line
--   Ctrl-U          paste             Ctrl-F          find
--   Ctrl-N          find next         Ctrl-G          go to line
--   Ctrl-A          line start        Ctrl-E          line end
--   Ctrl-B          page up           Ctrl-L          page down

local args = { ... }

local function termSize()
    local s = syscall.devctl(1, "size")
    return tonumber(s:match("^(%d+)")) or 80,
           tonumber(s:match(";(%d+)$")) or 24
end
local function tpos(x,y)  syscall.devctl(1,"spos",x,y) end
local function tfg(c)     syscall.devctl(1,"sfgc",c)   end
local function tbg(c)     syscall.devctl(1,"sbgc",c)   end
local function twrite(s)  if s and s~="" then syscall.write(1,s) end end
local function tclear()   syscall.devctl(1,"clear")    end

local W, H  = termSize()
local ROWS  = H - 2

local lines      = {""}
local cx         = 1
local cy         = 1
local scrollY    = 0
local dirty      = true
local fname      = nil
local msg        = ""
local msgErr     = false
local clip       = nil
local sPat       = ""
local sLine      = 0
local blinkState = false

local function absPath(p)
    if p:sub(1,1) == "/" then return p end
    local cwd = syscall.getcwd()
    cwd = cwd:gsub("/+$", "")
    return cwd .. "/" .. p
end

local function loadFile(path)
    if not syscall.exists(path) then
        lines = {""}; msg = "[new file]"; return
    end
    local fd = syscall.open(path, "r")
    local buf = ""
    while true do
        local c = syscall.read(fd, 4096)
        if not c or c == "" then break end
        buf = buf .. c
    end
    syscall.close(fd)
    lines = {}
    for ln in (buf.."\n"):gmatch("([^\n]*)\n") do
        table.insert(lines, ln)
    end
    if #lines > 1 and lines[#lines] == "" and buf:sub(-1) == "\n" then
        table.remove(lines)
    end
    if #lines == 0 then lines = {""} end
end

local function saveFile(path)
    local ok, err = pcall(function()
        local fd = syscall.open(path, "w")
        for i, ln in ipairs(lines) do
            syscall.write(fd, ln)
            if i < #lines then syscall.write(fd, "\n") end
        end
        syscall.write(fd, "\n")
        syscall.close(fd)
    end)
    if ok then
        msg = "Saved: "..path; msgErr = false
    else
        msg = "Save failed: "..tostring(err); msgErr = true
    end
end

local function wrappedRows(lineStr)
    return math.max(1, math.ceil(#lineStr / W))
end

local function logicalToScreen(li, col)
    return math.floor((col - 1) / W)
end

local function buildScreenMap()
    local map = {}
    local sr  = 0
    for li = 1, #lines do
        local len  = #lines[li]
        local nrows = wrappedRows(lines[li])
        for r = 0, nrows - 1 do
            sr = sr + 1
            map[sr] = {li, r * W + 1}
        end
    end
    return map, sr
end

local function cursorScreenRow(map)
    local offset = logicalToScreen(cy, cx)
    for sr, entry in ipairs(map) do
        if entry[1] == cy and math.floor((entry[2]-1)/W) == offset then
            return sr
        end
    end
    return 1
end

local function clampCx()
    local m = #lines[cy] + 1
    if cx > m then cx = m end
    if cx < 1 then cx = 1 end
end

local function clampScroll(map)
    local csr = cursorScreenRow(map)
    if csr - 1 < scrollY          then scrollY = csr - 1 end
    if csr - 1 >= scrollY + ROWS  then scrollY = csr - ROWS end
    if scrollY < 0                then scrollY = 0 end
end

local function pad(s, w)
    if #s >= w then return s:sub(1, w) end
    return s .. string.rep(" ", w - #s)
end

local function drawTop()
    tpos(1,1); tbg(4); tfg(16)
    local left  = " edit" .. (fname and (" - "..fname) or "")
    if dirty then left = left .. " [+]" end
    local right = tostring(cy)..","..tostring(cx).." "
    twrite(pad(left..string.rep(" ", math.max(1, W-#left-#right))..right, W))
    tbg(16); tfg(1)
end

local function drawBottom()
    tpos(1, H); tbg(4); tfg(16)
    if msg ~= "" then
        if msgErr then tbg(2) end
        twrite(pad(" "..msg, W))
        msg = ""; msgErr = false
    else
        twrite(pad(" ^W Save  ^X Quit+Save  ^P Quit  ^K Cut  ^U Paste  ^F Find  ^G Go", W))
    end
    tbg(16); tfg(1)
end

local function drawLines(map)
    local curSR    = cursorScreenRow(map)
    local curRowOffset = logicalToScreen(cy, cx)
    local curColInRow  = cx - curRowOffset * W

    for row = 1, ROWS do
        local sr = scrollY + row
        tpos(1, row + 1)
        local entry = map[sr]
        if entry then
            local li       = entry[1]
            local startCol = entry[2]
            local seg      = lines[li]:sub(startCol, startCol + W - 1)
            local isCursorRow = (sr == curSR)

            if isCursorRow then
                local ci = curColInRow
                ci = math.min(ci, #seg + 1)
                local before = seg:sub(1, ci-1)
                local curCh  = ci > #seg and " " or seg:sub(ci, ci)
                local after  = seg:sub(ci+1)

                tfg(1); tbg(16); twrite(before)
                if blinkState then tfg(16); tbg(1) else tfg(1); tbg(16) end
                twrite(curCh)
                tfg(1); tbg(16); twrite(after)
                local drawn = #before + 1 + #after
                if drawn < W then twrite(string.rep(" ", W - drawn)) end
            else
                if li == sLine and sPat ~= "" and entry[2] == 1 then
                    local s, e = seg:find(sPat)
                    if s then
                        tfg(1);  tbg(16); twrite(seg:sub(1,s-1))
                        tfg(16); tbg(3);  twrite(seg:sub(s,e))
                        tfg(1);  tbg(16); twrite(seg:sub(e+1))
                        twrite(string.rep(" ", W - #seg))
                    else
                        tfg(1); tbg(16); twrite(pad(seg, W))
                    end
                else
                    tfg(1); tbg(16); twrite(pad(seg, W))
                end
            end
        else
            tfg(13); tbg(16); twrite(pad("~", W)); tfg(1)
        end
    end
end

local function redraw()
    W, H = termSize(); ROWS = H - 2
    local map = buildScreenMap()
    clampScroll(map)
    drawTop()
    drawLines(map)
    drawBottom()
    tpos(1, H)
    tbg(16); tfg(1)
end

local function prompt(label, default)
    local inp = default or ""
    while true do
        tpos(1, H); tbg(3); tfg(16)
        twrite(pad(" "..label..inp.." ", W))
        tbg(16); tfg(1)
        local key = syscall.read(0)
        if not key or key == "" then sleep(0.02)
        elseif key == "" then return nil
        elseif key == "\n"  then return inp
        elseif key == "\b"  then if #inp > 0 then inp = inp:sub(1,-2) end
        else
            local b = key:byte(1)
            if b >= 32 and b < 127 then inp = inp..key:sub(1,1) end
        end
    end
end

local function insChar(c)
    local ln = lines[cy]
    lines[cy] = ln:sub(1,cx-1)..c..ln:sub(cx)
    cx = cx+1; dirty = true
end

local function delLeft()
    if cx > 1 then
        local ln = lines[cy]
        lines[cy] = ln:sub(1,cx-2)..ln:sub(cx)
        cx = cx-1; dirty = true
    elseif cy > 1 then
        local above = lines[cy-1]
        cx = #above+1
        lines[cy-1] = above..lines[cy]
        table.remove(lines, cy)
        cy = cy-1; dirty = true
    end
end

local function delRight()
    local ln = lines[cy]
    if cx <= #ln then
        lines[cy] = ln:sub(1,cx-1)..ln:sub(cx+1); dirty = true
    elseif cy < #lines then
        lines[cy] = ln..lines[cy+1]
        table.remove(lines, cy+1); dirty = true
    end
end

local function newline()
    local ln   = lines[cy]
    local pre  = ln:sub(1,cx-1)
    local post = ln:sub(cx)
    local ind  = pre:match("^(%s*)") or ""
    lines[cy]  = pre
    table.insert(lines, cy+1, ind..post)
    cy = cy+1; cx = #ind+1; dirty = true
end

local function cutLine()
    clip = lines[cy]
    table.remove(lines, cy)
    if #lines == 0 then lines = {""} end
    if cy > #lines then cy = #lines end
    cx = 1; dirty = true; msg = "Cut"
end

local function pasteLine()
    if not clip then msg = "Nothing to paste"; return end
    table.insert(lines, cy, clip)
    cy = cy+1; cx = 1; dirty = true; msg = "Pasted"
end

local function findNext()
    if sPat == "" then
        local p = prompt("Find: ", "")
        if not p or p == "" then dirty = true; return end
        sPat = p; sLine = 0
    end
    local start = sLine > 0 and sLine or cy
    for i = 1, #lines do
        local idx = (start-1+i) % #lines + 1
        if lines[idx]:find(sPat) then
            cy = idx; sLine = idx
            cx = lines[idx]:find(sPat) or 1
            msg = "Found: line "..idx; dirty = true; return
        end
    end
    msg = "Not found: "..sPat; msgErr = true; dirty = true
end

local function goToLine()
    local p = prompt("Go to line: ", "")
    if not p then dirty = true; return end
    local n = tonumber(p)
    if not n then msg = "Not a number"; msgErr = true; dirty = true; return end
    cy = math.max(1, math.min(#lines, math.floor(n)))
    cx = 1; msg = "Line "..cy; dirty = true
end

local function doSave()
    if not fname then
        local p = prompt("Save as: ", "")
        dirty = true
        if not p or p == "" then return false end
        fname = absPath(p)
    end
    saveFile(fname); dirty = true; return not msgErr
end

local function moveCursorUp(map)
    local csr = cursorScreenRow(map)
    if csr <= 1 then return end
    local prev = map[csr - 1]
    if not prev then return end
    local newLi  = prev[1]
    local newCol = prev[2] + (cx - 1) % W
    cx = math.min(newCol, #lines[newLi] + 1)
    cy = newLi
end

local function moveCursorDown(map)
    local csr = cursorScreenRow(map)
    local next = map[csr + 1]
    if not next then return end
    local newLi  = next[1]
    local newCol = next[2] + (cx - 1) % W
    cx = math.min(newCol, #lines[newLi] + 1)
    cy = newLi
end

if args[1] then
    fname = absPath(args[1])
    loadFile(fname)
end

tclear()

local running = true
while running do
    local map = buildScreenMap()

    local key = syscall.read(0)
    if key and key ~= "" then
        local b = key:byte(1)
        if     key == ""  then moveCursorUp(map); dirty=true
        elseif key == ""  then moveCursorDown(map); dirty=true
        elseif key == ""  then
            if cx <= #lines[cy] then cx=cx+1
            elseif cy < #lines then cy=cy+1; cx=1 end
            dirty=true
        elseif key == ""  then
            if cx > 1 then cx=cx-1
            elseif cy > 1 then cy=cy-1; cx=#lines[cy]+1 end
            dirty=true
        elseif key == ""  then cx=1; dirty=true
        elseif key == ""  then cx=#lines[cy]+1; dirty=true
        elseif key == "[5~" then for _=1,ROWS do moveCursorUp(map) end; dirty=true
        elseif key == "[6~" then for _=1,ROWS do moveCursorDown(map) end; dirty=true
        elseif key == "[3~" then delRight()
        elseif key == "\n"  then newline()
        elseif key == "\b"  then delLeft()
        elseif key == "\t"  then for _=1,4 do insChar(" ") end
        elseif b == 6  then
            local p=prompt("Find: ",sPat); dirty=true
            if p then sPat=p; sLine=0; findNext() end
        elseif b == 7  then goToLine()
        elseif b == 11 then cutLine()
        elseif b == 14 then
            if sPat=="" then
                local p=prompt("Find: ",""); dirty=true
                if p then sPat=p; sLine=0 end
            end
            findNext()
        elseif b == 16 then
            if dirty then
                local p=prompt("Unsaved changes. Quit? [y/N] ","")
                dirty=true
                if p and p:lower()=="y" then running=false end
            else running=false end
        elseif b == 21 then pasteLine()
        elseif b == 23 then doSave()
        elseif b == 24 then doSave(); running=false
        else
            if b >= 32 and b < 127 then insChar(key:sub(1,1)) end
        end
    end

    local curBlink = (math.floor(syscall.getUptime() / 500) % 2) == 0
    if curBlink ~= blinkState then
        blinkState = curBlink
        dirty = true
    end

    if dirty then
        clampCx()
        redraw()
        dirty = false
    end

    sleep(0.05)
end

tclear(); tfg(1); tbg(16); tpos(1,1)
print("edit: exited"..(fname and (" - "..fname) or ""))