import {
	PluginArrayMethods,
	latest,
	loadPlugin,
	markChanged,
	prepareCopy,
	handleCrossReference,
	ProxyArrayState
} from "../internal"

/**
 * Methods that directly modify the array in place.
 * These operate on the copy without creating per-element proxies:
 * - `push`, `pop`: Add/remove from end
 * - `shift`, `unshift`: Add/remove from start (marks all indices reassigned)
 * - `splice`: Add/remove at arbitrary position (marks all indices reassigned)
 * - `reverse`, `sort`: Reorder elements (marks all indices reassigned)
 */
type MutatingArrayMethod =
	| "push"
	| "pop"
	| "shift"
	| "unshift"
	| "splice"
	| "reverse"
	| "sort"

/**
 * Methods that read from the array without modifying it.
 * These fall into distinct categories based on return semantics:
 *
 * **Subset operations** (return drafts - mutations propagate):
 * - `filter`, `slice`: Return array of draft proxies
 * - `find`, `findLast`: Return single draft proxy or undefined
 *
 * **Transform operations** (return base values - mutations don't track):
 * - `concat`, `flat`: Create new structures, not subsets of original
 *
 * **Primitive-returning** (no draft needed):
 * - `findIndex`, `findLastIndex`, `indexOf`, `lastIndexOf`: Return numbers
 * - `some`, `every`, `includes`: Return booleans
 * - `join`, `toString`, `toLocaleString`: Return strings
 */
type NonMutatingArrayMethod =
	| "filter"
	| "slice"
	| "concat"
	| "flat"
	| "find"
	| "findIndex"
	| "findLast"
	| "findLastIndex"
	| "some"
	| "every"
	| "indexOf"
	| "lastIndexOf"
	| "includes"
	| "join"
	| "toString"
	| "toLocaleString"

/** Union of all array operation methods handled by the plugin. */
export type ArrayOperationMethod = MutatingArrayMethod | NonMutatingArrayMethod

/**
 * Enables optimized array method handling for Immer drafts.
 *
 * This plugin overrides array methods to avoid unnecessary Proxy creation during iteration,
 * significantly improving performance for array-heavy operations.
 *
 * **Mutating methods** (push, pop, shift, unshift, splice, sort, reverse):
 * Operate directly on the copy without creating per-element proxies.
 *
 * **Non-mutating methods** fall into categories:
 * - **Subset operations** (filter, slice, find, findLast): Return draft proxies - mutations track
 * - **Transform operations** (concat, flat): Return base values - mutations don't track
 * - **Primitive-returning** (indexOf, includes, some, every, etc.): Return primitives
 *
 * **Important**: Callbacks for overridden methods receive base values, not drafts.
 * This is the core performance optimization.
 *
 * @example
 * ```ts
 * import { enableArrayMethods, produce } from "immer"
 *
 * enableArrayMethods()
 *
 * const next = produce(state, draft => {
 *   // Optimized - no proxy creation per element
 *   draft.items.sort((a, b) => a.value - b.value)
 *
 *   // filter returns drafts - mutations propagate
 *   const filtered = draft.items.filter(x => x.value > 5)
 *   filtered[0].value = 999 // Affects draft.items[originalIndex]
 * })
 * ```
 *
 * @see https://immerjs.github.io/immer/array-methods
 */
export function enableArrayMethods() {
	const SHIFTING_METHODS = new Set<MutatingArrayMethod>(["shift", "unshift"])

	const QUEUE_METHODS = new Set<MutatingArrayMethod>(["push", "pop"])

	const RESULT_RETURNING_METHODS = new Set<MutatingArrayMethod>([
		...QUEUE_METHODS,
		...SHIFTING_METHODS
	])

	const REORDERING_METHODS = new Set<MutatingArrayMethod>(["reverse", "sort"])

	// Optimized method detection using array-based lookup
	const MUTATING_METHODS = new Set<MutatingArrayMethod>([
		...RESULT_RETURNING_METHODS,
		...REORDERING_METHODS,
		"splice"
	])

	const FIND_METHODS = new Set<NonMutatingArrayMethod>(["find", "findLast"])

	const NON_MUTATING_METHODS = new Set<NonMutatingArrayMethod>([
		"filter",
		"slice",
		"concat",
		"flat",
		...FIND_METHODS,
		"findIndex",
		"findLastIndex",
		"some",
		"every",
		"indexOf",
		"lastIndexOf",
		"includes",
		"join",
		"toString",
		"toLocaleString"
	])

	// Type guard for method detection
	function isMutatingArrayMethod(
		method: string
	): method is MutatingArrayMethod {
		return MUTATING_METHODS.has(method as any)
	}

	function isNonMutatingArrayMethod(
		method: string
	): method is NonMutatingArrayMethod {
		return NON_MUTATING_METHODS.has(method as any)
	}

	function isArrayOperationMethod(
		method: string
	): method is ArrayOperationMethod {
		return isMutatingArrayMethod(method) || isNonMutatingArrayMethod(method)
	}

	function enterOperation(
		state: ProxyArrayState,
		method: ArrayOperationMethod
	) {
		state.operationMethod = method
	}

	function exitOperation(state: ProxyArrayState) {
		state.operationMethod = undefined
	}

	// Shared utility functions for array method handlers
	function executeArrayMethod<T>(
		state: ProxyArrayState,
		operation: () => T,
		markLength = true
	): T {
		prepareCopy(state)
		const result = operation()
		markArrayChanged(state, markLength)
		return result
	}

	/**
	 * Marks the array (and its ancestors) as modified after a mutating operation.
	 *
	 * Kept separate from `executeArrayMethod` so that operations which turn out to
	 * be no-ops (e.g. `push()` with no arguments, `splice(i, 0)`, `pop()`/`shift()`
	 * on an empty array) can prepare a copy but skip marking, preserving Immer's
	 * structural-sharing guarantee that a change-free producer returns the base.
	 */
	function markArrayChanged(state: ProxyArrayState, markLength = true) {
		markChanged(state)
		if (markLength) state.assigned_!.set("length", true)
	}

	function markAllIndicesReassigned(state: ProxyArrayState) {
		state.allIndicesReassigned_ = true
		state.baseRefs_ = new Set(state.base_)
	}

	function normalizeSliceIndex(index: number, length: number): number {
		if (index < 0) {
			return Math.max(length + index, 0)
		}
		return Math.min(index, length)
	}

	/**
	 * Calls handleCrossReference for each value being inserted into the array,
	 * and marks the corresponding indices as assigned in `assigned_`.
	 *
	 * This ensures nested drafts inside inserted values (e.g. from spreading
	 * a draft object) are properly finalized, matching the behavior of the
	 * proxy set trap which calls handleCrossReference on every assignment.
	 *
	 * Without this, values containing draft proxies (like `{...state[0]}`)
	 * pushed via the array methods plugin would have their nested drafts
	 * revoked during finalization without being replaced by final values.
	 *
	 * The index is stringified because the proxy traps only ever see property
	 * names, so `assigned_` is keyed by string everywhere else. A numeric key
	 * would be invisible to the readers that look indices up by name, such as
	 * patch generation.
	 */
	function handleInsertedValues(
		state: ProxyArrayState,
		startIndex: number,
		values: any[]
	) {
		for (let i = 0; i < values.length; i++) {
			const index = "" + (startIndex + i)
			state.assigned_!.set(index, true)
			handleCrossReference(state, index, values[i])
		}
	}

	/**
	 * Handles mutating operations that add/remove elements (push, pop, shift, unshift, splice).
	 *
	 * Operates directly on `state.copy_` without creating per-element proxies.
	 * For shifting methods (shift, unshift), marks all indices as reassigned since
	 * indices shift.
	 *
	 * @returns For push/pop/shift/unshift: the native method result. For others: the draft.
	 */
	function handleSimpleOperation(
		state: ProxyArrayState,
		method: string,
		args: any[]
	) {
		// Detect no-op calls before creating a copy so structural sharing is
		// preserved: push/unshift with no arguments add nothing, and pop/shift
		// on an empty array remove nothing. The check must happen before
		// prepareCopy - a stray copy_ on an unmodified state would be picked
		// up by finalization of a parent Set and break identity there.
		const isInsert = method === "push" || method === "unshift"
		if (isInsert ? args.length === 0 : latest(state).length === 0) {
			// Match the native return values: push/unshift return the
			// (unchanged) length, pop/shift on an empty array return undefined
			return isInsert ? latest(state).length : undefined
		}

		prepareCopy(state)

		// For push/unshift, capture the length before the operation
		// so we can compute insertion indices for handleCrossReference
		const lengthBefore = state.copy_!.length

		const result = (state.copy_! as any)[method](...args)

		markArrayChanged(state)

		// Handle index reassignment for shifting methods
		if (SHIFTING_METHODS.has(method as MutatingArrayMethod)) {
			markAllIndicesReassigned(state)
		}

		// Handle cross-references for newly inserted values.
		// push appends at the end, unshift inserts at the beginning.
		if (method === "push") {
			handleInsertedValues(state, lengthBefore, args)
		} else if (method === "unshift") {
			handleInsertedValues(state, 0, args)
		}

		// Return appropriate value based on method
		return RESULT_RETURNING_METHODS.has(method as MutatingArrayMethod)
			? result
			: state.draft_
	}

	/**
	 * Handles reordering operations (reverse, sort) that change element order.
	 *
	 * Operates directly on `state.copy_` and marks all indices as reassigned
	 * since element positions change. Does not mark length as changed since
	 * these operations preserve array length.
	 *
	 * @returns The draft proxy for method chaining.
	 */
	function handleReorderingOperation(
		state: ProxyArrayState,
		method: string,
		args: any[]
	) {
		// Reordering an array with fewer than two elements cannot change it,
		// so preserve structural sharing and skip copying (see
		// handleSimpleOperation for why this must run before prepareCopy).
		if (latest(state).length <= 1) return state.draft_

		return executeArrayMethod(
			state,
			() => {
				;(state.copy_! as any)[method](...args)
				markAllIndicesReassigned(state)
				return state.draft_
			},
			false
		) // Don't mark length as changed
	}

	/**
	 * Creates an interceptor function for a specific array method.
	 *
	 * The interceptor wraps array method calls to:
	 * 1. Set `state.operationMethod` flag during execution (allows proxy `get` trap
	 *    to detect we're inside an optimized method and skip proxy creation)
	 * 2. Route to appropriate handler based on method type
	 * 3. Clean up the operation flag in `finally` block
	 *
	 * The `operationMethod` flag is the key mechanism that enables the proxy's `get`
	 * trap to return base values instead of creating nested proxies during iteration.
	 *
	 * @param state - The proxy array state
	 * @param originalMethod - Name of the array method being intercepted
	 * @returns Interceptor function that handles the method call
	 */
	function createMethodInterceptor(
		state: ProxyArrayState,
		originalMethod: string
	) {
		return function interceptedMethod(...args: any[]) {
			// Enter operation mode - this flag tells the proxy's get trap to return
			// base values instead of creating nested proxies during iteration
			const method = originalMethod as ArrayOperationMethod
			enterOperation(state, method)

			try {
				// Check if this is a mutating method
				if (isMutatingArrayMethod(method)) {
					// Direct method dispatch - no configuration lookup needed
					if (RESULT_RETURNING_METHODS.has(method)) {
						return handleSimpleOperation(state, method, args)
					}
					if (REORDERING_METHODS.has(method)) {
						return handleReorderingOperation(state, method, args)
					}

					if (method === "splice") {
						const insertCount = args.length > 2 ? args.length - 2 : 0

						// Detect no-op calls before creating a copy so structural
						// sharing is preserved (see handleSimpleOperation). A splice
						// removes nothing when called with no arguments, when the
						// normalized start is at/past the end, or when the delete
						// count coerces to less than 1. splice(start) with a single
						// argument removes everything from start onwards, so it must
						// not match. Exotic arguments that slip through are caught
						// by the post-copy check below.
						if (insertCount === 0) {
							const length = latest(state).length
							if (
								args.length === 0 ||
								normalizeSliceIndex(args[0] ?? 0, length) === length ||
								(args.length > 1 && !(args[1] >= 1))
							) {
								return []
							}
						}

						prepareCopy(state)
						const res = state.copy_!.splice(
							...(args as [number, number, ...any[]])
						)

						// Backstop for exotic arguments the pre-check above missed:
						// if nothing was removed and nothing inserted, the array is
						// unchanged and must not be marked as modified.
						if (res.length === 0 && insertCount === 0) {
							return res
						}

						markArrayChanged(state)
						markAllIndicesReassigned(state)
						// Handle cross-references for inserted values (args from index 2+)
						if (insertCount > 0) {
							const startIndex = normalizeSliceIndex(
								args[0] ?? 0,
								state.copy_!.length
							)
							handleInsertedValues(state, startIndex, args.slice(2))
						}
						return res
					}
				} else {
					// Handle non-mutating methods
					return handleNonMutatingOperation(state, method, args)
				}
			} finally {
				// Always exit operation mode - must be in finally to handle exceptions
				exitOperation(state)
			}
		}
	}

	/**
	 * Handles non-mutating array methods with different return semantics.
	 *
	 * **Subset operations** return draft proxies for mutation tracking:
	 * - `filter`, `slice`: Return `state.draft_[i]` for each selected element
	 * - `find`, `findLast`: Return `state.draft_[i]` for the found element
	 *
	 * This allows mutations on returned elements to propagate back to the draft:
	 * ```ts
	 * const filtered = draft.items.filter(x => x.value > 5)
	 * filtered[0].value = 999 // Mutates draft.items[originalIndex]
	 * ```
	 *
	 * **Transform operations** return base values (no draft tracking):
	 * - `concat`, `flat`: These create NEW arrays rather than selecting subsets.
	 *   Since the result structure differs from the original, tracking mutations
	 *   back to specific draft indices would be impractical/impossible.
	 *
	 * **Primitive operations** return the native result directly:
	 * - `indexOf`, `includes`, `some`, `every`, `join`, etc.
	 *
	 * @param state - The proxy array state
	 * @param method - The non-mutating method name
	 * @param args - Arguments passed to the method
	 * @returns Drafts for subset operations, base values for transforms, primitives otherwise
	 */
	function handleNonMutatingOperation(
		state: ProxyArrayState,
		method: NonMutatingArrayMethod,
		args: any[]
	) {
		const source = latest(state)

		// Methods that return arrays with selected items - need to return drafts
		if (method === "filter") {
			const predicate = args[0]
			const result: any[] = []

			// First pass: call predicate on base values to determine which items pass
			for (let i = 0; i < source.length; i++) {
				if (predicate(source[i], i, source)) {
					// Only create draft for items that passed the predicate
					result.push(state.draft_[i])
				}
			}

			return result
		}

		if (FIND_METHODS.has(method)) {
			const predicate = args[0]
			const isForward = method === "find"
			const step = isForward ? 1 : -1
			const start = isForward ? 0 : source.length - 1

			for (let i = start; i >= 0 && i < source.length; i += step) {
				if (predicate(source[i], i, source)) {
					return state.draft_[i]
				}
			}
			return undefined
		}

		if (method === "slice") {
			const rawStart = args[0] ?? 0
			const rawEnd = args[1] ?? source.length

			// Normalize negative indices
			const start = normalizeSliceIndex(rawStart, source.length)
			const end = normalizeSliceIndex(rawEnd, source.length)

			const result: any[] = []

			// Return drafts for items in the slice range
			for (let i = start; i < end; i++) {
				result.push(state.draft_[i])
			}

			return result
		}

		// For other methods, call on base array directly:
		// - indexOf, includes, join, toString: Return primitives, no draft needed
		// - concat, flat: Return NEW arrays (not subsets). Elements are base values.
		//   This is intentional - concat/flat create new data structures rather than
		//   selecting subsets of the original, making draft tracking impractical.
		return source[method as keyof typeof Array.prototype](...args)
	}

	loadPlugin(PluginArrayMethods, {
		createMethodInterceptor,
		isArrayOperationMethod,
		isMutatingArrayMethod
	})
}