/**
 * Safe Patch Applicator
 *
 * Applies LLM-generated code patches SAFELY.
 * Uses function-level replacement, NOT regex hacks.
 */

import * as fs from 'fs'
import * as path from 'path'
import {execSync} from 'child_process'

export interface PatchResult {
  success: boolean
  error?: string
  originalCode: string
  patchedCode: string
  backupPath?: string
}

export interface PatchRequest {
  filename: string
  // For function-level replacement
  functionName?: string
  functionStartLine?: number
  functionEndLine?: number
  // For line-range replacement (fallback)
  lineStart?: number
  lineEnd?: number
  // The new code to insert
  newCode: string
  language: string
}

/**
 * Apply a patch safely using the most appropriate strategy:
 * 1. Function-level AST-aware replacement (preferred)
 * 2. Line-range replacement with verification (fallback)
 */
export function applyPatch(
  workingDir: string,
  request: PatchRequest
): PatchResult {
  const absPath = path.resolve(workingDir, request.filename)

  if (!fs.existsSync(absPath)) {
    return {
      success: false,
      error: `File not found: ${absPath}`,
      originalCode: '',
      patchedCode: ''
    }
  }

  try {
    const originalCode = fs.readFileSync(absPath, 'utf8')
    const lines = originalCode.split('\n')

    // Strategy 1: Function-level replacement (preferred)
    if (
      request.functionName &&
      request.functionStartLine &&
      request.functionEndLine
    ) {
      const result = applyFunctionLevelPatch(lines, request)
      if (result.success) {
        // Write backup first
        const backupPath = `${absPath}.backup.${Date.now()}`
        fs.writeFileSync(backupPath, originalCode)

        // Write patched code
        fs.writeFileSync(absPath, result.patchedCode)

        return {
          ...result,
          originalCode,
          backupPath
        }
      }
      // Fall through to line-range if function-level fails
    }

    // Strategy 2: Line-range replacement
    if (request.lineStart && request.lineEnd) {
      const result = applyLineRangePatch(lines, request)
      if (result.success) {
        const backupPath = `${absPath}.backup.${Date.now()}`
        fs.writeFileSync(backupPath, originalCode)
        fs.writeFileSync(absPath, result.patchedCode)

        return {
          ...result,
          originalCode,
          backupPath
        }
      }
      return result
    }

    return {
      success: false,
      error: 'No valid patch strategy available',
      originalCode,
      patchedCode: originalCode
    }
  } catch (err: any) {
    return {
      success: false,
      error: `Patch application failed: ${err.message}`,
      originalCode: '',
      patchedCode: ''
    }
  }
}

/**
 * Apply function-level replacement
 * Replaces the entire function with the new implementation
 */
function applyFunctionLevelPatch(
  lines: string[],
  request: PatchRequest
): PatchResult {
  const originalCode = lines.join('\n')

  if (!request.functionStartLine || !request.functionEndLine) {
    return {
      success: false,
      error: 'Function boundaries not specified',
      originalCode,
      patchedCode: originalCode
    }
  }

  // Convert to 0-indexed
  const startIdx = request.functionStartLine - 1
  const endIdx = request.functionEndLine

  if (startIdx < 0 || endIdx > lines.length || startIdx >= endIdx) {
    return {
      success: false,
      error: `Invalid function boundaries: ${request.functionStartLine}-${request.functionEndLine}`,
      originalCode,
      patchedCode: originalCode
    }
  }

  // Verify the function exists at expected location (heuristic check)
  const originalFunction = lines.slice(startIdx, endIdx).join('\n')
  const functionName = request.functionName || 'unknown'

  // Simple heuristic: check if function name appears in the first line
  const firstLine = lines[startIdx].toLowerCase()
  const expectedName = functionName.toLowerCase()

  // Check for function patterns
  const hasFunctionPattern =
    firstLine.includes('function') ||
    firstLine.includes('=>') ||
    firstLine.includes('def ') || // Python
    firstLine.includes(`${expectedName}`)

  if (!hasFunctionPattern) {
    return {
      success: false,
      error: `Function "${functionName}" not found at expected location. Heuristic check failed.`,
      originalCode,
      patchedCode: originalCode
    }
  }

  // Normalize new code indentation
  const newCode = normalizeIndentation(request.newCode, lines[startIdx])

  // Build the patched file
  const beforeFunction = lines.slice(0, startIdx)
  const afterFunction = lines.slice(endIdx)

  const patchedLines = [...beforeFunction, newCode, ...afterFunction]

  const patchedCode = patchedLines.join('\n')

  // Safety check: basic syntax validation
  const syntaxError = quickSyntaxCheck(patchedCode, request.language)
  if (syntaxError) {
    return {
      success: false,
      error: `Syntax check failed: ${syntaxError}`,
      originalCode,
      patchedCode: originalCode
    }
  }

  return {
    success: true,
    originalCode,
    patchedCode
  }
}

/**
 * Apply line-range replacement (fallback)
 * Replaces specific lines with new code
 */
function applyLineRangePatch(
  lines: string[],
  request: PatchRequest
): PatchResult {
  const originalCode = lines.join('\n')

  if (!request.lineStart || !request.lineEnd) {
    return {
      success: false,
      error: 'Line range not specified',
      originalCode,
      patchedCode: originalCode
    }
  }

  // Convert to 0-indexed
  const startIdx = request.lineStart - 1
  const endIdx = request.lineEnd

  if (startIdx < 0 || endIdx > lines.length || startIdx >= endIdx) {
    return {
      success: false,
      error: `Invalid line range: ${request.lineStart}-${request.lineEnd}`,
      originalCode,
      patchedCode: originalCode
    }
  }

  // Get base indentation from the first line being replaced
  const baseIndent = getIndentation(lines[startIdx])

  // Normalize and apply new code indentation
  const newCode = normalizeIndentation(request.newCode, lines[startIdx])
  const newCodeLines = newCode.split('\n')

  // Build the patched file
  const beforeRange = lines.slice(0, startIdx)
  const afterRange = lines.slice(endIdx)

  const patchedLines = [...beforeRange, ...newCodeLines, ...afterRange]

  const patchedCode = patchedLines.join('\n')

  // Safety check
  const syntaxError = quickSyntaxCheck(patchedCode, request.language)
  if (syntaxError) {
    return {
      success: false,
      error: `Syntax check failed: ${syntaxError}`,
      originalCode,
      patchedCode: originalCode
    }
  }

  return {
    success: true,
    originalCode,
    patchedCode
  }
}

/**
 * Get indentation of a line
 */
function getIndentation(line: string): string {
  const match = line.match(/^(\s*)/)
  return match ? match[1] : ''
}

/**
 * Normalize indentation of new code to match original context
 */
function normalizeIndentation(newCode: string, referenceLine: string): string {
  const baseIndent = getIndentation(referenceLine)
  const lines = newCode.split('\n')

  // Find minimum indentation in new code
  let minIndent = Infinity
  for (const line of lines) {
    if (line.trim()) {
      const indent = getIndentation(line).length
      minIndent = Math.min(minIndent, indent)
    }
  }

  if (minIndent === Infinity) return newCode

  // Remove min indent from all lines and add base indent
  const normalized = lines.map(line => {
    if (!line.trim()) return ''
    const currentIndent = getIndentation(line).length
    const relativeIndent = currentIndent - minIndent
    return baseIndent + ' '.repeat(relativeIndent) + line.trimStart()
  })

  return normalized.join('\n')
}

/**
 * Semantic validation after patching
 * Runs tsc --noEmit, eslint, or npm test if available
 */
export interface ValidationResult {
  passed: boolean
  command: string
  stdout: string
  stderr: string
  exitCode: number
}

export async function validatePatchSemantically(
  workingDir: string,
  filename: string,
  language: string
): Promise<ValidationResult> {
  // Try validation commands in order of preference
  const validationCommands: Array<{cmd: string; label: string}> = []

  if (language === 'typescript') {
    // Check for TypeScript compiler
    validationCommands.push(
      {cmd: `npx tsc --noEmit ${filename}`, label: 'TypeScript compiler'},
      {cmd: 'npx tsc --noEmit', label: 'Project-wide TypeScript check'}
    )
  }

  // Check for ESLint
  validationCommands.push(
    {cmd: `npx eslint ${filename} --max-warnings=0`, label: 'ESLint'},
    {cmd: 'npx eslint . --max-warnings=0', label: 'Project-wide ESLint'}
  )

  // Check for npm test (if tests exist)
  validationCommands.push({
    cmd: 'npm test -- --passWithNoTests --testPathPattern=' + filename,
    label: 'npm test'
  })

  for (const {cmd, label} of validationCommands) {
    try {
      console.log(`[VALIDATION] Running ${label}...`)
      const stdout = execSync(cmd, {
        cwd: workingDir,
        encoding: 'utf8',
        timeout: 60000,
        stdio: ['pipe', 'pipe', 'pipe']
      })

      console.log(`[VALIDATION] ✓ ${label} passed`)
      return {
        passed: true,
        command: cmd,
        stdout,
        stderr: '',
        exitCode: 0
      }
    } catch (err: any) {
      // Command failed - this might be expected for missing tools
      if (
        err.status === 127 ||
        err.message?.includes('not found') ||
        err.message?.includes('ENOENT')
      ) {
        console.log(`[VALIDATION] ${label} not available, skipping...`)
        continue // Try next command
      }

      // Validation actually failed
      console.log(`[VALIDATION] ✗ ${label} failed (exit ${err.status})`)
      return {
        passed: false,
        command: cmd,
        stdout: err.stdout || '',
        stderr: err.stderr || '',
        exitCode: err.status || 1
      }
    }
  }

  // No validation tools available
  console.log(`[VALIDATION] ⚠ No semantic validation tools available`)
  return {
    passed: true, // Allow patch if we can't validate
    command: 'none',
    stdout: '',
    stderr: 'No validation tools available',
    exitCode: 0
  }
}

/**
 * Quick syntax validation
 * Not comprehensive, catches obvious issues
 */
function quickSyntaxCheck(code: string, language: string): string | null {
  // Basic brace/parenthesis balance check
  let braceCount = 0
  let parenCount = 0
  let bracketCount = 0
  let inString = false
  let stringChar = ''

  for (let i = 0; i < code.length; i++) {
    const char = code[i]
    const prevChar = i > 0 ? code[i - 1] : ''

    // Handle strings
    if (!inString && (char === '"' || char === "'" || char === '`')) {
      inString = true
      stringChar = char
      continue
    }
    if (inString && char === stringChar && prevChar !== '\\') {
      inString = false
      continue
    }

    if (inString) continue

    // Count braces
    if (char === '{') braceCount++
    else if (char === '}') braceCount--
    else if (char === '(') parenCount++
    else if (char === ')') parenCount--
    else if (char === '[') bracketCount++
    else if (char === ']') bracketCount--

    // Early termination on severe imbalance
    if (braceCount < -2 || parenCount < -2 || bracketCount < -2) {
      return `Unbalanced ${braceCount < 0 ? 'braces' : parenCount < 0 ? 'parentheses' : 'brackets'}`
    }
  }

  if (braceCount !== 0)
    return `Unbalanced braces: ${braceCount > 0 ? 'missing' : 'extra'} ${Math.abs(braceCount)} }`
  if (parenCount !== 0)
    return `Unbalanced parentheses: ${parenCount > 0 ? 'missing' : 'extra'} ${Math.abs(parenCount)} )`
  if (bracketCount !== 0)
    return `Unbalanced brackets: ${bracketCount > 0 ? 'missing' : 'extra'} ${Math.abs(bracketCount)} ]`

  // Language-specific checks
  if (language === 'typescript' || language === 'javascript') {
    // Check for common syntax issues
    if (/\bfunction\s*\([^)]*\)\s*[^=>{]/.test(code)) {
      return 'Function without body'
    }
  }

  return null
}

/**
 * Rollback a patch using backup file
 */
export function rollbackPatch(
  backupPath: string,
  originalPath: string
): boolean {
  try {
    if (!fs.existsSync(backupPath)) {
      console.error(`[PATCH] Backup not found: ${backupPath}`)
      return false
    }

    fs.copyFileSync(backupPath, originalPath)
    console.log(`[PATCH] Rolled back ${originalPath} from ${backupPath}`)
    return true
  } catch (err: any) {
    console.error(`[PATCH] Rollback failed: ${err.message}`)
    return false
  }
}

/**
 * Clean up backup files older than specified age
 */
export function cleanupOldBackups(
  workingDir: string,
  maxAgeMs: number = 24 * 60 * 60 * 1000
): void {
  try {
    const files = fs.readdirSync(workingDir)
    const now = Date.now()

    for (const file of files) {
      if (file.includes('.backup.')) {
        const backupPath = path.join(workingDir, file)
        const stats = fs.statSync(backupPath)
        const age = now - stats.mtimeMs

        if (age > maxAgeMs) {
          fs.unlinkSync(backupPath)
          console.log(`[PATCH] Cleaned up old backup: ${file}`)
        }
      }
    }
  } catch (err: any) {
    console.error(`[PATCH] Cleanup failed: ${err.message}`)
  }
}