import memoize from 'lodash-es/memoize.js'
import {
  extractOutputRedirections,
  splitCommandWithOperators,
} from './commands.js'
import type { Node } from './parser.js'
import {
  analyzeCommand,
  type TreeSitterAnalysis,
} from './treeSitterAnalysis.js'

export type OutputRedirection = {
  target: string
  operator: '>' | '>>'
}

/**
 * Interface for parsed command implementations.
 * Both tree-sitter and regex fallback implementations conform to this.
 */
export interface IParsedCommand {
  readonly originalCommand: string
  toString(): string
  getPipeSegments(): string[]
  withoutOutputRedirections(): string
  getOutputRedirections(): OutputRedirection[]
  /**
   * Returns tree-sitter analysis data if available.
   * Returns null for the regex fallback implementation.
   */
  getTreeSitterAnalysis(): TreeSitterAnalysis | null
}

/**
 * @deprecated Legacy regex/shell-quote path. Only used when tree-sitter is
 * unavailable. The primary gate is parseForSecurity (ast.ts).
 *
 * Regex-based fallback implementation using shell-quote parser.
 * Used when tree-sitter is not available.
 * Exported for testing purposes.
 */
export class RegexParsedCommand_DEPRECATED implements IParsedCommand {
  readonly originalCommand: string

  constructor(command: string) {
    this.originalCommand = command
  }

  toString(): string {
    return this.originalCommand
  }

  getPipeSegments(): string[] {
    try {
      const parts = splitCommandWithOperators(this.originalCommand)
      const segments: string[] = []
      let currentSegment: string[] = []

      for (const part of parts) {
        if (part === '|') {
          if (currentSegment.length > 0) {
            segments.push(currentSegment.join(' '))
            currentSegment = []
          }
        } else {
          currentSegment.push(part)
        }
      }

      if (currentSegment.length > 0) {
        segments.push(currentSegment.join(' '))
      }

      return segments.length > 0 ? segments : [this.originalCommand]
    } catch {
      return [this.originalCommand]
    }
  }

  withoutOutputRedirections(): string {
    if (!this.originalCommand.includes('>')) {
      return this.originalCommand
    }
    const { commandWithoutRedirections, redirections } =
      extractOutputRedirections(this.originalCommand)
    return redirections.length > 0
      ? commandWithoutRedirections
      : this.originalCommand
  }

  getOutputRedirections(): OutputRedirection[] {
    const { redirections } = extractOutputRedirections(this.originalCommand)
    return redirections
  }

  getTreeSitterAnalysis(): TreeSitterAnalysis | null {
    return null
  }
}

type RedirectionNode = OutputRedirection & {
  startIndex: number
  endIndex: number
}

function visitNodes(node: Node, visitor: (node: Node) => void): void {
  visitor(node)
  for (const child of node.children) {
    visitNodes(child, visitor)
  }
}

function extractPipePositions(rootNode: Node): number[] {
  const pipePositions: number[] = []
  visitNodes(rootNode, node => {
    if (node.type === 'pipeline') {
      for (const child of node.children) {
        if (child.type === '|') {
          pipePositions.push(child.startIndex)
        }
      }
    }
  })
  // visitNodes is depth-first. For `a | b && c | d`, the outer `list` nests
  // the second pipeline as a sibling of the first, so the outer `|` is
  // visited before the inner one — positions arrive out of order.
  // getPipeSegments iterates them to slice left-to-right, so sort here.
  return pipePositions.sort((a, b) => a - b)
}

function extractRedirectionNodes(rootNode: Node): RedirectionNode[] {
  const redirections: RedirectionNode[] = []
  visitNodes(rootNode, node => {
    if (node.type === 'file_redirect') {
      const children = node.children
      const op = children.find(c => c.type === '>' || c.type === '>>')
      const target = children.find(c => c.type === 'word')
      if (op && target) {
        redirections.push({
          startIndex: node.startIndex,
          endIndex: node.endIndex,
          target: target.text,
          operator: op.type as '>' | '>>',
        })
      }
    }
  })
  return redirections
}

class TreeSitterParsedCommand implements IParsedCommand {
  readonly originalCommand: string
  // Tree-sitter's startIndex/endIndex are UTF-8 byte offsets, but JS
  // String.slice() uses UTF-16 code-unit indices. For ASCII they coincide;
  // for multi-byte code points (e.g. `—` U+2014: 3 UTF-8 bytes, 1 code unit)
  // they diverge and slicing the string directly lands mid-token. Slicing
  // the UTF-8 Buffer with tree-sitter's byte offsets and decoding back to
  // string is correct regardless of code-point width.
  private readonly commandBytes: Buffer
  private readonly pipePositions: number[]
  private readonly redirectionNodes: RedirectionNode[]
  private readonly treeSitterAnalysis: TreeSitterAnalysis

  constructor(
    command: string,
    pipePositions: number[],
    redirectionNodes: RedirectionNode[],
    treeSitterAnalysis: TreeSitterAnalysis,
  ) {
    this.originalCommand = command
    this.commandBytes = Buffer.from(command, 'utf8')
    this.pipePositions = pipePositions
    this.redirectionNodes = redirectionNodes
    this.treeSitterAnalysis = treeSitterAnalysis
  }

  toString(): string {
    return this.originalCommand
  }

  getPipeSegments(): string[] {
    if (this.pipePositions.length === 0) {
      return [this.originalCommand]
    }

    const segments: string[] = []
    let currentStart = 0

    for (const pipePos of this.pipePositions) {
      const segment = this.commandBytes
        .subarray(currentStart, pipePos)
        .toString('utf8')
        .trim()
      if (segment) {
        segments.push(segment)
      }
      currentStart = pipePos + 1
    }

    const lastSegment = this.commandBytes
      .subarray(currentStart)
      .toString('utf8')
      .trim()
    if (lastSegment) {
      segments.push(lastSegment)
    }

    return segments
  }

  withoutOutputRedirections(): string {
    if (this.redirectionNodes.length === 0) return this.originalCommand

    const sorted = [...this.redirectionNodes].sort(
      (a, b) => b.startIndex - a.startIndex,
    )

    let result = this.commandBytes
    for (const redir of sorted) {
      result = Buffer.concat([
        result.subarray(0, redir.startIndex),
        result.subarray(redir.endIndex),
      ])
    }
    return result.toString('utf8').trim().replace(/\s+/g, ' ')
  }

  getOutputRedirections(): OutputRedirection[] {
    return this.redirectionNodes.map(({ target, operator }) => ({
      target,
      operator,
    }))
  }

  getTreeSitterAnalysis(): TreeSitterAnalysis {
    return this.treeSitterAnalysis
  }
}

const getTreeSitterAvailable = memoize(async (): Promise<boolean> => {
  try {
    const { parseCommand } = await import('./parser.js')
    const testResult = await parseCommand('echo test')
    return testResult !== null
  } catch {
    return false
  }
})

/**
 * Build a TreeSitterParsedCommand from a pre-parsed AST root. Lets callers
 * that already have the tree skip the redundant native.parse that
 * ParsedCommand.parse would do.
 */
export function buildParsedCommandFromRoot(
  command: string,
  root: Node,
): IParsedCommand {
  const pipePositions = extractPipePositions(root)
  const redirectionNodes = extractRedirectionNodes(root)
  const analysis = analyzeCommand(root, command)
  return new TreeSitterParsedCommand(
    command,
    pipePositions,
    redirectionNodes,
    analysis,
  )
}

async function doParse(command: string): Promise<IParsedCommand | null> {
  if (!command) return null

  const treeSitterAvailable = await getTreeSitterAvailable()
  if (treeSitterAvailable) {
    try {
      const { parseCommand } = await import('./parser.js')
      const data = await parseCommand(command)
      if (data) {
        // Native NAPI parser returns plain JS objects (no WASM handles);
        // nothing to free — extract directly.
        return buildParsedCommandFromRoot(command, data.rootNode)
      }
    } catch {
      // Fall through to regex implementation
    }
  }

  // Fallback to regex implementation
  return new RegexParsedCommand_DEPRECATED(command)
}

// Single-entry cache: legacy callers (bashCommandIsSafeAsync,
// buildSegmentWithoutRedirections) may call ParsedCommand.parse repeatedly
// with the same command string. Each parse() is ~1 native.parse + ~6 tree
// walks, so caching the most recent command skips the redundant work.
// Size-1 bound avoids leaking TreeSitterParsedCommand instances.
let lastCmd: string | undefined
let lastResult: Promise<IParsedCommand | null> | undefined

/**
 * ParsedCommand provides methods for working with shell commands.
 * Uses tree-sitter when available for quote-aware parsing,
 * falls back to regex-based parsing otherwise.
 */
export const ParsedCommand = {
  /**
   * Parse a command string and return a ParsedCommand instance.
   * Returns null if parsing fails completely.
   */
  parse(command: string): Promise<IParsedCommand | null> {
    if (command === lastCmd && lastResult !== undefined) {
      return lastResult
    }
    lastCmd = command
    lastResult = doParse(command)
    return lastResult
  },
}