import type { Plugin } from "@opencode-ai/plugin"
import { spawn } from "bun"
import { appendFileSync } from "fs"

/**
 * tmux-panes plugin
 *
 * When opencode spawns a background subagent, this plugin automatically opens
 * a new tmux pane showing that subagent's live TUI via `opencode attach`.
 *
 * Layout:
 *   - First subagent: horizontal 60/40 split — main pane on left, subagent on right
 *   - Additional subagents: stacked vertically in the right column
 *   - Panes close automatically when subagent sessions end
 *
 * Only activates when running inside a tmux session (TMUX env var is set).
 *
 * Debug log: /tmp/opencode-tmux-debug.log
 */

const DEBUG_LOG = "/tmp/opencode-tmux-debug.log"
const log = (msg: string) =>
	appendFileSync(DEBUG_LOG, `[${new Date().toISOString()}] ${msg}\n`)

const isInsideTmux = () => Boolean(process.env.TMUX)
const getCurrentPaneId = () => process.env.TMUX_PANE

const plugin: Plugin = async (ctx) => {
	if (!isInsideTmux()) return {}

	const sessions = new Map<string, string>() // sessionId → tmux paneId
	const sourcePaneId = getCurrentPaneId()
	const serverUrl = ctx.serverUrl?.toString() ?? ""
	log(`plugin init — serverUrl=${serverUrl} sourcePaneId=${sourcePaneId}`)

	// Ordered list of pane IDs in the right column.
	// Empty = no right column yet; length > 0 = right column exists.
	const rightColumnPanes: string[] = []

	return {
		event: async ({ event }) => {
			// Spawn a new pane when a subagent session is created
			if (event.type === "session.created") {
				const info = (event as any).properties?.info
				// parentID presence distinguishes subagents from the root session
				if (!info?.id || !info?.parentID) return
				const sessionId: string = info.id
				if (sessions.has(sessionId)) return

				// Wrap the attach command: on failure, show the error and keep the
			// pane open for 30 s so we can read it before it disappears.
			const attachCmd = `opencode attach ${serverUrl} --session ${sessionId}`
			const cmd = `bash -c '${attachCmd}; _exit=$?; echo "--- exit: $_exit ---" >> ${DEBUG_LOG}; [ $_exit -ne 0 ] && sleep 30'`
			log(`spawning pane — cmd: ${attachCmd}`)

				let args: string[]
				if (rightColumnPanes.length === 0) {
					// First subagent: open a horizontal split, giving the new (right)
					// pane 40% of the window width so the main pane keeps 60%.
					args = [
						"tmux",
						"split-window",
						"-h", // horizontal split — new pane appears on the right
						"-p", "40", // new pane gets 40% of window width
						"-d", // don't focus the new pane
						"-P",
						"-F",
						"#{pane_id}",
						...(sourcePaneId ? ["-t", sourcePaneId] : []),
						cmd,
					]
				} else {
					// Additional subagents: stack vertically within the right column
					// by splitting the last right-column pane horizontally.
					const lastRightPane = rightColumnPanes[rightColumnPanes.length - 1]
					args = [
						"tmux",
						"split-window",
						"-v", // vertical split — new pane stacks below the target
						"-d", // don't focus the new pane
						"-P",
						"-F",
						"#{pane_id}",
						"-t", lastRightPane,
						cmd,
					]
				}

				const proc = spawn(args, { stdout: "pipe", stderr: "pipe" })
				const paneId = (await new Response(proc.stdout).text()).trim()
			const exitCode = await proc.exited
			log(`split-window exit=${exitCode} paneId=${paneId}`)
			if (exitCode === 0 && paneId) {
				sessions.set(sessionId, paneId)
				rightColumnPanes.push(paneId)
			}
			}

			// Kill the pane when the subagent session ends
			if (event.type === "session.deleted") {
				const info = (event as any).properties?.info
				const paneId = sessions.get(info?.id)
				if (paneId) {
					spawn(["tmux", "kill-pane", "-t", paneId], {
						stdout: "ignore",
						stderr: "ignore",
					})
					sessions.delete(info.id)
					const idx = rightColumnPanes.indexOf(paneId)
					if (idx !== -1) rightColumnPanes.splice(idx, 1)
				}
			}
		},
	}
}

export default plugin