import { tool } from "@opencode-ai/plugin"
import { readFileSync, existsSync } from "fs"
import { join } from "path"
import { resolveWorktree, debugLog } from "../state-io.ts"

function stripComments(src: string): string {
  let out = src.replace(/([^:])\/\/[^\n]*/g, "$1")
  out = out.replace(/\/\*[\s\S]*?\*\//g, "")
  out = out.replace(/\n{3,}/g, "\n\n")
  return out.trim()
}

function extractSignatures(src: string): string {
  const patterns = [
    /^export\s+(default\s+)?(async\s+)?function\s+/,
    /^export\s+(default\s+)?class\s+/,
    /^export\s+(type|interface)\s+/,
    /^export\s+(const|let|var)\s+\w+/,
    /^(async\s+)?function\s+\w+/,
    /^class\s+\w+/,
    /^interface\s+\w+/,
    /^type\s+\w+\s*=/,
    /^(const|let|var)\s+\w+\s*[:=]/,
    /^import\s+/,
  ]
  return src
    .split("\n")
    .filter((line) => patterns.some((p) => p.test(line.trimStart())))
    .join("\n")
}

function extractMinimal(src: string): string {
  const lines = src.split("\n")
  const head = lines.slice(0, 10)
  const exports = lines.filter((l) => /^export\s/.test(l.trimStart()))
  const seen = new Set<string>()
  return [...head, "", "// ...", ...exports]
    .filter((l) => {
      if (seen.has(l)) return false
      seen.add(l)
      return true
    })
    .join("\n")
}

export default tool({
  description:
    "Compress a source file for agent context. 0 LLM tokens. " +
    "Modes: full (strip comments), signatures (declarations only), minimal (header + exports).",
  args: {
    file: tool.schema.string().describe("File path relative to project root or absolute"),
    mode: tool.schema.enum(["full", "signatures", "minimal"]).describe("Compression level"),
  },
  async execute(args, context) {
    const wt = resolveWorktree(context.worktree)
    const abs = args.file.startsWith("/")
      ? args.file
      : join(wt, args.file)

    if (!existsSync(abs)) throw new Error(`File not found: ${args.file}`)

    const src = readFileSync(abs, "utf-8")
    const originalLines = src.split("\n").length

    let compressed: string
    switch (args.mode) {
      case "full":
        compressed = stripComments(src)
        break
      case "signatures":
        compressed = extractSignatures(src)
        break
      case "minimal":
        compressed = extractMinimal(src)
        break
      default:
        compressed = src
    }

    const compressedLines = compressed.split("\n").length
    const savedLines = originalLines - compressedLines
    const ratio = originalLines > 0
      ? Math.round((1 - compressedLines / originalLines) * 100)
      : 0

    debugLog("tool", "compress_executed", {
      file: args.file,
      mode: args.mode,
      original_lines: originalLines,
      compressed_lines: compressedLines,
      saved_lines: savedLines,
      reduction_percent: ratio,
    })

    return JSON.stringify({
      file: args.file,
      mode: args.mode,
      content: compressed,
      original_lines: originalLines,
      compressed_lines: compressedLines,
      saved_lines: savedLines,
      reduction: `${ratio}%`,
    })
  },
})