/**
 * Git worktree create — pure validation and command-building functions.
 * No pi SDK dependencies for testability.
 */

// ─── Type Definitions ──────────────────────────────────────────────

/** Error returned when a worktree operation fails. */
export interface WorktreeError {
	/** Human-readable error message from git or validation. */
	message: string;
	/** Suggested fix for the user. */
	suggestion?: string;
}

/** Parameters for creating a new worktree. */
export interface CreateWorktreeParams {
	/** Path for the new worktree (relative or absolute). */
	path: string;
	/** Branch name to check out. */
	branch: string;
	/** Whether to create the branch if it doesn't exist. Defaults to true. */
	createBranch?: boolean;
}

// ─── Validation ────────────────────────────────────────────────────

/**
 * Validate input parameters for creating a worktree.
 *
 * Checks that path and branch name are non-empty and well-formed.
 * Branch names follow git conventions: no spaces, no leading/trailing whitespace,
 * no special characters like ~, ^, . at start or ?, *, [, ], ", ' in the middle (except / for nesting).
 *
 * @param worktreePath - Path for the new worktree
 * @param branchName - Branch name to check out
 * @returns null if valid, or a WorktreeError describing the problem
 */
export function validateCreateWorktreeInput(
	worktreePath: string,
	branchName: string,
): WorktreeError | null {
	// Validate path is non-empty
	if (!worktreePath || !worktreePath.trim()) {
		return {
			message: "Path cannot be empty.",
			suggestion: "Provide a valid path for the new worktree (e.g., '../worktrees/feature-x').",
		};
	}

	// Validate branch name is non-empty
	if (!branchName || !branchName.trim()) {
		return {
			message: "Branch name cannot be empty.",
			suggestion: "Provide a valid branch name (e.g., 'feature-x' or 'bugfix/issue-42').",
		};
	}

	// Validate branch name doesn't contain spaces
	if (branchName.includes(" ")) {
		return {
			message: `Branch name '${branchName}' contains invalid characters (spaces).`,
			suggestion: "Use hyphens or underscores instead of spaces (e.g., 'feature-x' not 'my feature').",
		};
	}

	// Validate branch name doesn't start/end with special chars
	if (/^[\/\-~^\.]/.test(branchName) || /[\/\-\.\s]$/.test(branchName)) {
		return {
			message: `Branch name '${branchName}' starts or ends with an invalid character.`,
			suggestion: "Branch names should start with a letter and not end with '/', '-', '.', or whitespace.",
		};
	}

	// Validate branch name doesn't contain dangerous characters
	if (/[?*\[\]"'\\]/.test(branchName)) {
		return {
			message: `Branch name '${branchName}' contains invalid characters.`,
			suggestion: "Avoid characters like ?, *, [, ], \", ' in branch names.",
		};
	}

	return null;
}

// ─── Path Validation ──────────────────────────────────────────────

/**
 * Check if the target path already exists and return an error if so.
 *
 * @param worktreePath - Path to check
 * @param checkExists - Function that checks if a path exists (injected for testability)
 * @returns null if path is free, or a WorktreeError with the exact message format
 */
export function validatePathDoesNotExist(
	worktreePath: string,
	checkExists: (path: string) => boolean,
): WorktreeError | null {
	if (checkExists(worktreePath)) {
		return {
			message: `Path '${worktreePath}' already exists.`,
			suggestion: "Choose a different location.",
		};
	}
	return null;
}

// ─── Branch Validation ──────────────────────────────────────────────

/**
 * Check if the target branch is the same as the current branch.
 *
 * @param targetBranch - The branch we want to create the worktree on
 * @param currentBranch - The currently checked out branch
 * @returns true if they match (worktree creation should be refused)
 */
export function isCurrentBranch(targetBranch: string, currentBranch: string): boolean {
	return targetBranch === currentBranch;
}

// ─── Command Building ──────────────────────────────────────────────

/**
 * Build the `git worktree add` command arguments.
 *
 * Uses `-b` flag when createBranch is true to create a new branch.
 * Without `-b`, checks out an existing branch.
 *
 * @param params - Worktree creation parameters
 * @returns Array of command arguments (excluding 'git' itself)
 */
export function buildWorktreeAddCommand(params: CreateWorktreeParams): string[] {
	const { path: worktreePath, branch, createBranch = true } = params;

	const args = ["worktree", "add"];

	if (createBranch) {
		args.push("-b", branch);
	} else {
		args.push(branch);
	}

	args.push(worktreePath);

	return args;
}