-- renderer.lua — output formatting and ANSI sequences.
-- Phase 0: assistant text plain-printed with `CMD: ` lines highlighted;
-- exec output framed with the exit code on the closing rule.
-- Phase 1: assistant_delta + assistant_flush for streaming render. CMD:
-- highlighting in streaming mode is deferred (Q12); deltas print raw, the
-- §6 substrate `CMD: ` line is still extractable by executor afterwards.
-- Syntax highlighting hooks land in Phase 6 (was Phase 5 pre-MCP renumber).

local M = {}

local A = {
    reset = "\27[0m",
    bold  = "\27[1m",
    dim   = "\27[2m",
    cyan  = "\27[36m",
    red   = "\27[31m",
}

local function emit(...) io.write(...); io.flush() end

-- Print assistant response text. Lines beginning with `CMD: ` (per the §3
-- substrate-locked extraction marker) are emitted bold+cyan so the user
-- can spot the suggestion without scanning prose.
function M.assistant(text)
    for line in ((text or "") .. "\n"):gmatch("([^\n]*)\n") do
        if line:sub(1, 5) == "CMD: " then
            emit(A.bold, A.cyan, line, A.reset, "\n")
        else
            emit(line, "\n")
        end
    end
end

-- Phase 1: executor.exec streams output live to stdout (PTY multiplex), so
-- the frame is split — exec_begin before the spawn, exec_end after wait().
-- The body is not re-rendered here; live output lands directly between the
-- two rules.
function M.exec_begin()
    emit(A.dim, "─── exec output ───", A.reset, "\n")
end

function M.exec_end(exit_code)
    if exit_code and exit_code ~= 0 then
        emit(A.dim, "─── exit ", A.reset,
             A.red, tostring(exit_code), A.reset,
             A.dim, " ───", A.reset, "\n")
    else
        emit(A.dim, "─── exit 0 ───", A.reset, "\n")
    end
end

-- Single-line dim status (e.g. §8 eviction notice, model switch confirms).
function M.status(line)
    emit(A.dim, "[aish] ", tostring(line), A.reset, "\n")
end

-- Streaming assistant output. Phase 1: deltas are written raw — the §6 CMD:
-- highlighting from M.assistant() is not applied incrementally because
-- mid-line cursor manipulation isn't worth the complexity for Phase 1.
-- Q12 (PHASE1.md §10) tracks the upgrade. The full assistant text is still
-- captured by repl.lua and CMD: extraction works against the reassembled
-- string after the stream ends.

local stream_buf = nil   -- non-nil while a stream is in progress

function M.assistant_delta(chunk)
    if not chunk or chunk == "" then return end
    if stream_buf == nil then stream_buf = "" end
    stream_buf = stream_buf .. chunk
    emit(chunk)
end

function M.assistant_flush()
    if stream_buf == nil then return end
    if not stream_buf:match("\n$") then emit("\n") end
    stream_buf = nil
end

return M