import fs from "fs/promises"
import { existsSync } from "fs"
import path from "path"

import simpleGit, { SimpleGit, CleanOptions } from "simple-git"

import { CheckpointStrategy, CheckpointService, CheckpointServiceOptions } from "./types"

export interface LocalCheckpointServiceOptions extends CheckpointServiceOptions {}

/**
 * The CheckpointService provides a mechanism for storing a snapshot of the
 * current VSCode workspace each time a Roo Code tool is executed. It uses Git
 * under the hood.
 *
 * HOW IT WORKS
 *
 * Two branches are used:
 *  - A main branch for normal operation (the branch you are currently on).
 *  - A hidden branch for storing checkpoints.
 *
 * Saving a checkpoint:
 *  - A temporary branch is created to store the current state.
 *  - All changes (including untracked files) are staged and committed on the temp branch.
 *  - The hidden branch is reset to match main.
 *  - The temporary branch commit is cherry-picked onto the hidden branch.
 *  - The workspace is restored to its original state and the temp branch is deleted.
 *
 * Restoring a checkpoint:
 *  - The workspace is restored to the state of the specified checkpoint using
 *    `git restore` and `git clean`.
 *
 * This approach allows for:
 *  - Non-destructive version control (main branch remains untouched).
 *  - Preservation of the full history of checkpoints.
 *  - Safe restoration to any previous checkpoint.
 *  - Atomic checkpoint operations with proper error recovery.
 *
 * NOTES
 *
 *  - Git must be installed.
 *  - If the current working directory is not a Git repository, we will
 *    initialize a new one with a .gitkeep file.
 *  - If you manually edit files and then restore a checkpoint, the changes
 *    will be lost. Addressing this adds some complexity to the implementation
 *    and it's not clear whether it's worth it.
 */

export class LocalCheckpointService implements CheckpointService {
	private static readonly USER_NAME = "Roo Code"
	private static readonly USER_EMAIL = "support@roocode.com"
	private static readonly CHECKPOINT_BRANCH = "roo-code-checkpoints"
	private static readonly STASH_BRANCH = "roo-code-stash"

	public readonly strategy: CheckpointStrategy = "local"
	public readonly version = 1

	public get baseHash() {
		return this._baseHash
	}

	constructor(
		public readonly taskId: string,
		public readonly git: SimpleGit,
		public readonly workspaceDir: string,
		private readonly mainBranch: string,
		private _baseHash: string,
		private readonly hiddenBranch: string,
		private readonly log: (message: string) => void,
	) {}

	private async ensureBranch(expectedBranch: string) {
		const branch = await this.git.revparse(["--abbrev-ref", "HEAD"])

		if (branch.trim() !== expectedBranch) {
			throw new Error(`Git branch mismatch: expected '${expectedBranch}' but found '${branch}'`)
		}
	}

	public async getDiff({ from, to }: { from?: string; to?: string }) {
		const result = []

		if (!from) {
			from = this.baseHash
		}

		const { files } = await this.git.diffSummary([`${from}..${to}`])

		for (const file of files.filter((f) => !f.binary)) {
			const relPath = file.file
			const absPath = path.join(this.workspaceDir, relPath)
			const before = await this.git.show([`${from}:${relPath}`]).catch(() => "")

			const after = to
				? await this.git.show([`${to}:${relPath}`]).catch(() => "")
				: await fs.readFile(absPath, "utf8").catch(() => "")

			result.push({
				paths: { relative: relPath, absolute: absPath },
				content: { before, after },
			})
		}

		return result
	}

	private async restoreMain({
		branch,
		stashSha,
		force = false,
	}: {
		branch: string
		stashSha: string
		force?: boolean
	}) {
		let currentBranch = await this.git.revparse(["--abbrev-ref", "HEAD"])

		if (currentBranch !== this.mainBranch) {
			if (force) {
				try {
					await this.git.checkout(["-f", this.mainBranch])
				} catch (err) {
					this.log(
						`[restoreMain] failed to force checkout ${this.mainBranch}: ${err instanceof Error ? err.message : String(err)}`,
					)
				}
			} else {
				try {
					await this.git.checkout(this.mainBranch)
				} catch (err) {
					this.log(
						`[restoreMain] failed to checkout ${this.mainBranch}: ${err instanceof Error ? err.message : String(err)}`,
					)

					// Escalate to a forced checkout if we can't checkout the
					// main branch under normal circumstances.
					currentBranch = await this.git.revparse(["--abbrev-ref", "HEAD"])

					if (currentBranch !== this.mainBranch) {
						await this.git.checkout(["-f", this.mainBranch]).catch(() => {})
					}
				}
			}
		}

		currentBranch = await this.git.revparse(["--abbrev-ref", "HEAD"])

		if (currentBranch !== this.mainBranch) {
			throw new Error(`Unable to restore ${this.mainBranch}`)
		}

		if (stashSha) {
			this.log(`[restoreMain] applying stash ${stashSha}`)

			try {
				await this.git.raw(["stash", "apply", "--index", stashSha])
			} catch (err) {
				this.log(`[restoreMain] Failed to apply stash: ${err instanceof Error ? err.message : String(err)}`)
			}
		}

		this.log(`[restoreMain] restoring from ${branch} branch`)

		try {
			await this.git.raw(["restore", "--source", branch, "--worktree", "--", "."])
		} catch (err) {
			this.log(`[restoreMain] Failed to restore branch: ${err instanceof Error ? err.message : String(err)}`)
		}
	}

	public async saveCheckpoint(message: string) {
		const startTime = Date.now()

		await this.ensureBranch(this.mainBranch)

		const stashSha = (await this.git.raw(["stash", "create"])).trim()
		const latestSha = await this.git.revparse([this.hiddenBranch])

		/**
		 * PHASE: Create stash
		 * Mutations:
		 *   - Create branch
		 *   - Change branch
		 */
		const stashBranch = `${LocalCheckpointService.STASH_BRANCH}-${Date.now()}`
		await this.git.checkout(["-b", stashBranch])
		this.log(`[saveCheckpoint] created and checked out ${stashBranch}`)

		/**
		 * Phase: Stage stash
		 * Mutations: None
		 * Recovery:
		 *   - UNDO: Create branch
		 *   - UNDO: Change branch
		 */
		try {
			await this.git.add(["-A"])
		} catch (err) {
			this.log(
				`[saveCheckpoint] failed in stage stash phase: ${err instanceof Error ? err.message : String(err)}`,
			)
			await this.restoreMain({ branch: stashBranch, stashSha, force: true })
			await this.git.branch(["-D", stashBranch]).catch(() => {})
			throw err
		}

		/**
		 * Phase: Commit stash
		 * Mutations:
		 *   - Commit stash
		 *   - Change branch
		 * Recovery:
		 *   - UNDO: Create branch
		 *   - UNDO: Change branch
		 */
		let stashCommit

		try {
			stashCommit = await this.git.commit(message, undefined, { "--no-verify": null })
			this.log(`[saveCheckpoint] stashCommit: ${message} -> ${JSON.stringify(stashCommit)}`)
		} catch (err) {
			this.log(
				`[saveCheckpoint] failed in stash commit phase: ${err instanceof Error ? err.message : String(err)}`,
			)
			await this.restoreMain({ branch: stashBranch, stashSha, force: true })
			await this.git.branch(["-D", stashBranch]).catch(() => {})
			throw err
		}

		if (!stashCommit) {
			this.log("[saveCheckpoint] no stash commit")
			await this.restoreMain({ branch: stashBranch, stashSha })
			await this.git.branch(["-D", stashBranch])
			return undefined
		}

		/**
		 * PHASE: Diff
		 * Mutations:
		 *   - Checkout hidden branch
		 * Recovery:
		 *   - UNDO: Create branch
		 *   - UNDO: Change branch
		 *   - UNDO: Commit stash
		 */
		let diff

		try {
			diff = await this.git.diff([latestSha, stashBranch])
		} catch (err) {
			this.log(`[saveCheckpoint] failed in diff phase: ${err instanceof Error ? err.message : String(err)}`)
			await this.restoreMain({ branch: stashBranch, stashSha, force: true })
			await this.git.branch(["-D", stashBranch]).catch(() => {})
			throw err
		}

		if (!diff) {
			this.log("[saveCheckpoint] no diff")
			await this.restoreMain({ branch: stashBranch, stashSha })
			await this.git.branch(["-D", stashBranch])
			return undefined
		}

		/**
		 * PHASE: Reset
		 * Mutations:
		 *   - Reset hidden branch
		 * Recovery:
		 *   - UNDO: Create branch
		 *   - UNDO: Change branch
		 *   - UNDO: Commit stash
		 */
		try {
			await this.git.checkout(this.hiddenBranch)
			this.log(`[saveCheckpoint] checked out ${this.hiddenBranch}`)
			await this.git.reset(["--hard", this.mainBranch])
			this.log(`[saveCheckpoint] reset ${this.hiddenBranch}`)
		} catch (err) {
			this.log(`[saveCheckpoint] failed in reset phase: ${err instanceof Error ? err.message : String(err)}`)
			await this.restoreMain({ branch: stashBranch, stashSha, force: true })
			await this.git.branch(["-D", stashBranch]).catch(() => {})
			throw err
		}

		/**
		 * PHASE: Cherry pick
		 * Mutations:
		 *   - Hidden commit (NOTE: reset on hidden branch no longer needed in
		 *     success scenario.)
		 * Recovery:
		 *   - UNDO: Create branch
		 *   - UNDO: Change branch
		 *   - UNDO: Commit stash
		 *   - UNDO: Reset hidden branch
		 */
		let commit = ""

		try {
			try {
				await this.git.raw(["cherry-pick", stashBranch])
			} catch (err) {
				// Check if we're in the middle of a cherry-pick.
				// If the cherry-pick resulted in an empty commit (e.g., only
				// deletions) then complete it with --allow-empty.
				// Otherwise, rethrow the error.
				if (existsSync(path.join(this.workspaceDir, ".git/CHERRY_PICK_HEAD"))) {
					await this.git.raw(["commit", "--allow-empty", "--no-edit"])
				} else {
					throw err
				}
			}

			commit = await this.git.revparse(["HEAD"])
			this.log(`[saveCheckpoint] cherry-pick commit = ${commit}`)
		} catch (err) {
			this.log(
				`[saveCheckpoint] failed in cherry pick phase: ${err instanceof Error ? err.message : String(err)}`,
			)
			await this.git.reset(["--hard", latestSha]).catch(() => {})
			await this.restoreMain({ branch: stashBranch, stashSha, force: true })
			await this.git.branch(["-D", stashBranch]).catch(() => {})
			throw err
		}

		await this.restoreMain({ branch: stashBranch, stashSha })
		await this.git.branch(["-D", stashBranch])

		// We've gotten reports that checkpoints can be slow in some cases, so
		// we'll log the duration of the checkpoint save.
		const duration = Date.now() - startTime
		this.log(`[saveCheckpoint] saved checkpoint ${commit} in ${duration}ms`)

		return { commit }
	}

	public async restoreCheckpoint(commitHash: string) {
		const startTime = Date.now()
		await this.ensureBranch(this.mainBranch)
		await this.git.clean([CleanOptions.FORCE, CleanOptions.RECURSIVE])
		await this.git.raw(["restore", "--source", commitHash, "--worktree", "--", "."])
		const duration = Date.now() - startTime
		this.log(`[restoreCheckpoint] restored checkpoint ${commitHash} in ${duration}ms`)
	}

	public static async create({ taskId, workspaceDir, log = console.log }: LocalCheckpointServiceOptions) {
		const git = simpleGit(workspaceDir)
		const version = await git.version()

		if (!version?.installed) {
			throw new Error(`Git is not installed. Please install Git if you wish to use checkpoints.`)
		}

		if (!workspaceDir || !existsSync(workspaceDir)) {
			throw new Error(`Base directory is not set or does not exist.`)
		}

		const { currentBranch, currentSha, hiddenBranch } = await LocalCheckpointService.initRepo(git, {
			taskId,
			workspaceDir,
			log,
		})

		log(
			`[create] taskId = ${taskId}, workspaceDir = ${workspaceDir}, currentBranch = ${currentBranch}, currentSha = ${currentSha}, hiddenBranch = ${hiddenBranch}`,
		)

		return new LocalCheckpointService(taskId, git, workspaceDir, currentBranch, currentSha, hiddenBranch, log)
	}

	private static async initRepo(
		git: SimpleGit,
		{ taskId, workspaceDir, log }: Required<LocalCheckpointServiceOptions>,
	) {
		const isExistingRepo = existsSync(path.join(workspaceDir, ".git"))

		if (!isExistingRepo) {
			await git.init()
			log(`[initRepo] Initialized new Git repository at ${workspaceDir}`)
		}

		const globalUserName = await git.getConfig("user.name", "global")
		const localUserName = await git.getConfig("user.name", "local")
		const userName = localUserName.value || globalUserName.value

		const globalUserEmail = await git.getConfig("user.email", "global")
		const localUserEmail = await git.getConfig("user.email", "local")
		const userEmail = localUserEmail.value || globalUserEmail.value

		// Prior versions of this service indiscriminately set the local user
		// config, and it should not override the global config. To address
		// this we remove the local user config if it matches the default
		// user name and email and there's a global config.
		if (globalUserName.value && localUserName.value === LocalCheckpointService.USER_NAME) {
			await git.raw(["config", "--unset", "--local", "user.name"])
		}

		if (globalUserEmail.value && localUserEmail.value === LocalCheckpointService.USER_EMAIL) {
			await git.raw(["config", "--unset", "--local", "user.email"])
		}

		// Only set user config if not already configured.
		if (!userName) {
			await git.addConfig("user.name", LocalCheckpointService.USER_NAME)
		}

		if (!userEmail) {
			await git.addConfig("user.email", LocalCheckpointService.USER_EMAIL)
		}

		if (!isExistingRepo) {
			// We need at least one file to commit, otherwise the initial
			// commit will fail, unless we use the `--allow-empty` flag.
			// However, using an empty commit causes problems when restoring
			// the checkpoint (i.e. the `git restore` command doesn't work
			// for empty commits).
			await fs.writeFile(path.join(workspaceDir, ".gitkeep"), "")
			await git.add(".gitkeep")
			const commit = await git.commit("Initial commit")

			if (!commit.commit) {
				throw new Error("Failed to create initial commit")
			}

			log(`[initRepo] Initial commit: ${commit.commit}`)
		}

		const currentBranch = await git.revparse(["--abbrev-ref", "HEAD"])
		const currentSha = await git.revparse(["HEAD"])

		const hiddenBranch = `${LocalCheckpointService.CHECKPOINT_BRANCH}-${taskId}`
		const branchSummary = await git.branch()

		if (!branchSummary.all.includes(hiddenBranch)) {
			await git.checkoutBranch(hiddenBranch, currentBranch)
			await git.checkout(currentBranch)
		}

		return { currentBranch, currentSha, hiddenBranch }
	}
}