import { Effect, Schema } from "effect"
import * as path from "path"
import { FSUtil } from "@opencode-ai/core/fs-util"
import * as Bom from "../util/bom"

export const PatchSchema = Schema.Struct({
  patchText: Schema.String.annotate({ description: "The full patch text that describes all changes to be made" }),
})

export type PatchParams = Schema.Schema.Type

// Core types matching the Rust implementation
export interface ApplyPatchArgs {
  patch: string
  hunks: Hunk[]
  workdir?: string
}

export type Hunk =
  | { type: "add"; path: string; contents: string }
  | { type: "delete"; path: string }
  | { type: "update"; path: string; move_path?: string; chunks: UpdateFileChunk[] }

export interface UpdateFileChunk {
  old_lines: string[]
  new_lines: string[]
  change_context?: string
  is_end_of_file?: boolean
}

export interface ApplyPatchAction {
  changes: Map
  patch: string
  cwd: string
}

export type ApplyPatchFileChange =
  | { type: "add"; content: string }
  | { type: "delete"; content: string }
  | { type: "update"; unified_diff: string; move_path?: string; new_content: string }

export interface AffectedPaths {
  added: string[]
  modified: string[]
  deleted: string[]
}

export enum ApplyPatchError {
  ParseError = "ParseError",
  IoError = "IoError",
  ComputeReplacements = "ComputeReplacements",
  ImplicitInvocation = "ImplicitInvocation",
}

export enum MaybeApplyPatch {
  Body = "Body",
  ShellParseError = "ShellParseError",
  PatchParseError = "PatchParseError",
  NotApplyPatch = "NotApplyPatch",
}

export enum MaybeApplyPatchVerified {
  Body = "Body",
  ShellParseError = "ShellParseError",
  CorrectnessError = "CorrectnessError",
  NotApplyPatch = "NotApplyPatch",
}

// Parser implementation
function parsePatchHeader(
  lines: string[],
  startIdx: number,
): { filePath: string; movePath?: string; nextIdx: number } | null {
  const line = lines[startIdx]

  if (line.startsWith("*** Add File:")) {
    const filePath = line.slice("*** Add File:".length).trim()
    return filePath ? { filePath, nextIdx: startIdx + 1 } : null
  }

  if (line.startsWith("*** Delete File:")) {
    const filePath = line.slice("*** Delete File:".length).trim()
    return filePath ? { filePath, nextIdx: startIdx + 1 } : null
  }

  if (line.startsWith("*** Update File:")) {
    const filePath = line.slice("*** Update File:".length).trim()
    let movePath: string | undefined
    let nextIdx = startIdx + 1

    // Check for move directive
    if (nextIdx < lines.length && lines[nextIdx].startsWith("*** Move to:")) {
      movePath = lines[nextIdx].slice("*** Move to:".length).trim()
      nextIdx++
    }

    return filePath ? { filePath, movePath, nextIdx } : null
  }

  return null
}

function parseUpdateFileChunks(lines: string[], startIdx: number): { chunks: UpdateFileChunk[]; nextIdx: number } {
  const chunks: UpdateFileChunk[] = []
  let i = startIdx

  while (i < lines.length && !lines[i].startsWith("***")) {
    if (lines[i].startsWith("@@")) {
      // Parse context line
      const contextLine = lines[i].substring(2).trim()
      i++

      const oldLines: string[] = []
      const newLines: string[] = []
      let isEndOfFile = false

      // Parse change lines
      while (i < lines.length && !lines[i].startsWith("@@") && !lines[i].startsWith("***")) {
        const changeLine = lines[i]

        if (changeLine === "*** End of File") {
          isEndOfFile = true
          i++
          break
        }

        if (changeLine.startsWith(" ")) {
          // Keep line - appears in both old and new
          const content = changeLine.substring(1)
          oldLines.push(content)
          newLines.push(content)
        } else if (changeLine.startsWith("-")) {
          // Remove line - only in old
          oldLines.push(changeLine.substring(1))
        } else if (changeLine.startsWith("+")) {
          // Add line - only in new
          newLines.push(changeLine.substring(1))
        }

        i++
      }

      chunks.push({
        old_lines: oldLines,
        new_lines: newLines,
        change_context: contextLine || undefined,
        is_end_of_file: isEndOfFile || undefined,
      })
    } else {
      i++
    }
  }

  return { chunks, nextIdx: i }
}

function parseAddFileContent(lines: string[], startIdx: number): { content: string; nextIdx: number } {
  let content = ""
  let i = startIdx

  while (i < lines.length && !lines[i].startsWith("***")) {
    if (lines[i].startsWith("+")) {
      content += lines[i].substring(1) + "\n"
    }
    i++
  }

  // Remove trailing newline
  if (content.endsWith("\n")) {
    content = content.slice(0, -1)
  }

  return { content, nextIdx: i }
}

function stripHeredoc(input: string): string {
  // Match heredoc patterns like: cat  boolean

function tryMatch(lines: string[], pattern: string[], startIndex: number, compare: Comparator, eof: boolean): number {
  // If EOF anchor, try matching from end of file first
  if (eof) {
    const fromEnd = lines.length - pattern.length
    if (fromEnd >= startIndex) {
      let matches = true
      for (let j = 0; j < pattern.length; j++) {
        if (!compare(lines[fromEnd + j], pattern[j])) {
          matches = false
          break
        }
      }
      if (matches) return fromEnd
    }
  }

  // Forward search from startIndex
  for (let i = startIndex; i  a === b, eof)
  if (exact !== -1) return exact

  // Pass 2: rstrip (trim trailing whitespace)
  const rstrip = tryMatch(lines, pattern, startIndex, (a, b) => a.trimEnd() === b.trimEnd(), eof)
  if (rstrip !== -1) return rstrip

  // Pass 3: trim (both ends)
  const trim = tryMatch(lines, pattern, startIndex, (a, b) => a.trim() === b.trim(), eof)
  if (trim !== -1) return trim

  // Pass 4: normalized (Unicode punctuation to ASCII)
  const normalized = tryMatch(
    lines,
    pattern,
    startIndex,
    (a, b) => normalizeUnicode(a.trim()) === normalizeUnicode(b.trim()),
    eof,
  )
  return normalized
}

function generateUnifiedDiff(oldContent: string, newContent: string): string {
  const oldLines = oldContent.split("\n")
  const newLines = newContent.split("\n")

  // Simple diff generation - in a real implementation you'd use a proper diff algorithm
  let diff = "@@ -1 +1 @@\n"

  // Find changes (simplified approach)
  const maxLen = Math.max(oldLines.length, newLines.length)
  let hasChanges = false

  for (let i = 0; i < maxLen; i++) {
    const oldLine = oldLines[i] || ""
    const newLine = newLines[i] || ""

    if (oldLine !== newLine) {
      if (oldLine) diff += `-${oldLine}\n`
      if (newLine) diff += `+${newLine}\n`
      hasChanges = true
    } else if (oldLine) {
      diff += ` ${oldLine}\n`
    }
  }

  return hasChanges ? diff : ""
}

// Apply hunks to filesystem
export const applyHunksToFiles = Effect.fn("Patch.applyHunksToFiles")(function* (hunks: Hunk[]) {
  if (hunks.length === 0) {
    return yield* Effect.fail(new Error("No files were modified."))
  }

  const fs = yield* FSUtil.Service

  const added: string[] = []
  const modified: string[] = []
  const deleted: string[] = []

  for (const hunk of hunks) {
    switch (hunk.type) {
      case "add": {
        yield* fs.writeWithDirs(hunk.path, hunk.contents)
        added.push(hunk.path)
        yield* Effect.logInfo(`Added file: ${hunk.path}`)
        break
      }

      case "delete": {
        yield* fs.remove(hunk.path)
        deleted.push(hunk.path)
        yield* Effect.logInfo(`Deleted file: ${hunk.path}`)
        break
      }

      case "update": {
        const originalText = yield* fs.readFileString(hunk.path)
        const fileUpdate = deriveNewContentsFromChunks(hunk.path, hunk.chunks, originalText)

        if (hunk.move_path) {
          yield* fs.writeWithDirs(hunk.move_path, Bom.join(fileUpdate.content, fileUpdate.bom))
          yield* fs.remove(hunk.path)
          modified.push(hunk.move_path)
          yield* Effect.logInfo(`Moved file: ${hunk.path} -> ${hunk.move_path}`)
        } else {
          yield* fs.writeWithDirs(hunk.path, Bom.join(fileUpdate.content, fileUpdate.bom))
          modified.push(hunk.path)
          yield* Effect.logInfo(`Updated file: ${hunk.path}`)
        }
        break
      }
    }
  }

  return { added, modified, deleted } satisfies AffectedPaths
})

// Main patch application function
export const applyPatch = Effect.fn("Patch.applyPatch")(function* (patchText: string) {
  const { hunks } = parsePatch(patchText)
  return yield* applyHunksToFiles(hunks)
})

type MaybeApplyPatchVerifiedResult =
  | { type: MaybeApplyPatchVerified.Body; action: ApplyPatchAction }
  | { type: MaybeApplyPatchVerified.CorrectnessError; error: Error }
  | { type: MaybeApplyPatchVerified.NotApplyPatch }

// Effectful verified-parse: needs FSUtil.Service to read existing files
export const maybeParseApplyPatchVerified = Effect.fn("Patch.maybeParseApplyPatchVerified")(function* (
  argv: string[],
  cwd: string,
) {
  // Detect implicit patch invocation (raw patch without apply_patch command)
  if (argv.length === 1) {
    try {
      parsePatch(argv[0])
      return {
        type: MaybeApplyPatchVerified.CorrectnessError,
        error: new Error(ApplyPatchError.ImplicitInvocation),
      } satisfies MaybeApplyPatchVerifiedResult
    } catch {
      // Not a patch, continue
    }
  }

  const result = maybeParseApplyPatch(argv)

  switch (result.type) {
    case MaybeApplyPatch.Body: {
      const fs = yield* FSUtil.Service
      const args = result.args
      const effectiveCwd = args.workdir ? path.resolve(cwd, args.workdir) : cwd
      const changes = new Map()

      for (const hunk of args.hunks) {
        const resolvedPath = path.resolve(
          effectiveCwd,
          hunk.type === "update" && hunk.move_path ? hunk.move_path : hunk.path,
        )

        switch (hunk.type) {
          case "add":
            changes.set(resolvedPath, {
              type: "add",
              content: hunk.contents,
            })
            break

          case "delete": {
            const deletePath = path.resolve(effectiveCwd, hunk.path)
            const content = yield* fs.readFileString(deletePath).pipe(Effect.catch(() => Effect.succeed(undefined)))
            if (content === undefined) {
              return {
                type: MaybeApplyPatchVerified.CorrectnessError,
                error: new Error(`Failed to read file for deletion: ${deletePath}`),
              } satisfies MaybeApplyPatchVerifiedResult
            }
            changes.set(resolvedPath, {
              type: "delete",
              content,
            })
            break
          }

          case "update": {
            const updatePath = path.resolve(effectiveCwd, hunk.path)
            const originalText = yield* fs
              .readFileString(updatePath)
              .pipe(
                Effect.catch((cause) =>
                  Effect.succeed(new Error(`Failed to read file ${updatePath}: ${cause}`, { cause })),
                ),
              )
            if (originalText instanceof Error) {
              return {
                type: MaybeApplyPatchVerified.CorrectnessError,
                error: originalText,
              } satisfies MaybeApplyPatchVerifiedResult
            }
            try {
              const fileUpdate = deriveNewContentsFromChunks(updatePath, hunk.chunks, originalText)
              changes.set(resolvedPath, {
                type: "update",
                unified_diff: fileUpdate.unified_diff,
                move_path: hunk.move_path ? path.resolve(effectiveCwd, hunk.move_path) : undefined,
                new_content: fileUpdate.content,
              })
            } catch (error) {
              return {
                type: MaybeApplyPatchVerified.CorrectnessError,
                error: error as Error,
              } satisfies MaybeApplyPatchVerifiedResult
            }
            break
          }
        }
      }

      return {
        type: MaybeApplyPatchVerified.Body,
        action: {
          changes,
          patch: args.patch,
          cwd: effectiveCwd,
        },
      } satisfies MaybeApplyPatchVerifiedResult
    }

    case MaybeApplyPatch.PatchParseError:
      return {
        type: MaybeApplyPatchVerified.CorrectnessError,
        error: result.error,
      } satisfies MaybeApplyPatchVerifiedResult

    case MaybeApplyPatch.NotApplyPatch:
      return { type: MaybeApplyPatchVerified.NotApplyPatch } satisfies MaybeApplyPatchVerifiedResult
  }
})

export * as Patch from "."