/**
 * Local tracking checkouts for remote Git references, one per remote and
 * branch. Each checkout permanently tracks a single ref: the requested branch
 * when the cache key has one, otherwise the remote default branch. Content
 * follows "newest wins": refresh fetches and hard-resets, so readers may
 * observe the checkout move underneath them.
 */
import path from "path"
import { Context, Effect, Layer, Schema } from "effect"
import { FSUtil } from "@opencode-ai/util/fs-util"
import { Git } from "./git"
import { Global } from "@opencode-ai/util/global"
import { Repository } from "./repository"
import { AbsolutePath } from "./schema"
import { makeGlobalNode } from "@opencode-ai/util/effect/app-node"
import { EffectFlock } from "@opencode-ai/util/effect-flock"

export type Result = {
  readonly repository: string
  readonly host: string
  readonly remote: string
  readonly localPath: string
  readonly status: "cached" | "cloned" | "refreshed"
  readonly head?: string
  readonly branch?: string
}

export type EnsureInput = {
  readonly reference: Repository.RemoteReference
  readonly refresh?: boolean
  readonly branch?: string
}

export class InvalidBranchError extends Schema.TaggedErrorClass<InvalidBranchError>()(
  "RepositoryCacheInvalidBranchError",
  {
    branch: Schema.String,
    message: Schema.String,
  },
) {}

export class CloneFailedError extends Schema.TaggedErrorClass<CloneFailedError>()("RepositoryCacheCloneFailedError", {
  repository: Schema.String,
  message: Schema.String,
}) {}

export class FetchFailedError extends Schema.TaggedErrorClass<FetchFailedError>()("RepositoryCacheFetchFailedError", {
  repository: Schema.String,
  message: Schema.String,
}) {}

export class CheckoutFailedError extends Schema.TaggedErrorClass<CheckoutFailedError>()(
  "RepositoryCacheCheckoutFailedError",
  {
    repository: Schema.String,
    branch: Schema.String,
    message: Schema.String,
  },
) {}

export class ResetFailedError extends Schema.TaggedErrorClass<ResetFailedError>()("RepositoryCacheResetFailedError", {
  repository: Schema.String,
  message: Schema.String,
}) {}

export class LockFailedError extends Schema.TaggedErrorClass<LockFailedError>()("RepositoryCacheLockFailedError", {
  localPath: Schema.String,
  message: Schema.String,
}) {}

export class CacheOperationError extends Schema.TaggedErrorClass<CacheOperationError>()(
  "RepositoryCacheOperationError",
  {
    operation: Schema.String,
    path: Schema.String,
    message: Schema.String,
  },
) {}

export type Error =
  | InvalidBranchError
  | CloneFailedError
  | FetchFailedError
  | CheckoutFailedError
  | ResetFailedError
  | LockFailedError
  | CacheOperationError

export interface Interface {
  readonly ensure: (input: EnsureInput) => Effect.Effect<Result, Error>
}

export class Service extends Context.Service<Service, Interface>()("@opencode/RepositoryCache") {}

export function isError(error: unknown): error is Error {
  return (
    error instanceof InvalidBranchError ||
    error instanceof CloneFailedError ||
    error instanceof FetchFailedError ||
    error instanceof CheckoutFailedError ||
    error instanceof ResetFailedError ||
    error instanceof LockFailedError ||
    error instanceof CacheOperationError
  )
}

export const validateBranch = Effect.fn("RepositoryCache.validateBranch")(function* (branch: string) {
  return yield* Effect.try({
    try: () => Repository.validateBranch(branch),
    catch: (error) => new InvalidBranchError({ branch, message: errorMessage(error) }),
  })
})

const layer: Layer.Layer<Service, never, FSUtil.Service | Git.Service | EffectFlock.Service | Global.Service> =
  Layer.effect(
    Service,
    Effect.gen(function* () {
      const fs = yield* FSUtil.Service
      const git = yield* Git.Service
      const flock = yield* EffectFlock.Service
      const global = yield* Global.Service

      return Service.of({
        ensure: Effect.fn("RepositoryCache.ensure")(function* (input) {
          if (input.branch) yield* validateBranch(input.branch)

          const repository = input.reference.label
          const localPath = Repository.cachePath(global.repos, input.reference, input.branch)
          const cloneTarget = Repository.parse(input.reference.remote) ?? input.reference

          return yield* flock
            .withLock(
              Effect.gen(function* () {
                yield* cacheOperation(fs.ensureDir(path.dirname(localPath)), "ensure cache directory", localPath)

                const existing = yield* git.repo.discover(AbsolutePath.make(localPath))
                const origin = existing ? yield* git.remote.get(existing) : undefined
                const originReference = origin ? Repository.parse(origin) : undefined
                // Discovery walks upward, so an enclosing repository with a
                // matching origin could masquerade as the cache entry; reuse
                // requires the checkout to live exactly at the cache path.
                const worktree = existing ? yield* fs.resolve(localPath) : undefined
                const reuse = Boolean(
                  existing &&
                    existing.worktree === worktree &&
                    originReference &&
                    Repository.same(originReference, cloneTarget),
                )
                if (!reuse && (yield* fs.existsSafe(localPath))) {
                  yield* cacheOperation(fs.remove(localPath, { recursive: true }), "remove stale cache", localPath)
                }

                const status = !reuse
                  ? ("cloned" as const)
                  : input.refresh
                    ? ("refreshed" as const)
                    : ("cached" as const)

                if (status === "cloned") {
                  yield* git.repo
                    .clone({
                      remote: input.reference.remote,
                      directory: AbsolutePath.make(localPath),
                      branch: input.branch,
                    })
                    .pipe(Effect.mapError((error) => new CloneFailedError({ repository, message: error.message })))
                }

                if (status === "refreshed") {
                  if (!existing)
                    return yield* new FetchFailedError({ repository, message: "Repository is unavailable" })
                  yield* git.sync
                    .fetchRemotes(existing)
                    .pipe(Effect.mapError((error) => new FetchFailedError({ repository, message: error.message })))

                  if (input.branch) {
                    yield* git.sync
                      .fetchBranch(existing, { branch: input.branch })
                      .pipe(Effect.mapError((error) => new FetchFailedError({ repository, message: error.message })))
                  }

                  // Checking out the tracked ref before resetting keeps the
                  // checkout self-healing even if it was left on another
                  // branch.
                  const branch = input.branch ?? (yield* git.history.defaultRemoteBranch(existing))
                  if (branch) {
                    yield* git.sync
                      .checkoutRemoteBranch(existing, { branch })
                      .pipe(
                        Effect.mapError(
                          (error) => new CheckoutFailedError({ repository, branch, message: error.message }),
                        ),
                      )
                  }

                  const target = branch ?? (yield* git.history.branch(existing))
                  yield* git.sync
                    .resetHard(existing, target ? `origin/${target}` : "HEAD")
                    .pipe(Effect.mapError((error) => new ResetFailedError({ repository, message: error.message })))
                }

                const checkout = yield* git.repo.discover(AbsolutePath.make(localPath))

                return {
                  repository,
                  host: input.reference.host,
                  remote: input.reference.remote,
                  localPath,
                  status,
                  head: checkout ? yield* git.history.head(checkout) : undefined,
                  branch: checkout ? yield* git.history.branch(checkout) : undefined,
                } satisfies Result
              }),
              `repository-cache:${localPath}`,
            )
            .pipe(
              Effect.mapError((error) =>
                isError(error) ? error : new LockFailedError({ localPath, message: errorMessage(error) }),
              ),
            )
        }),
      })
    }),
  )

export const node = makeGlobalNode({
  service: Service,
  layer,
  deps: [EffectFlock.node, FSUtil.node, Git.node, Global.node],
})

function errorMessage(error: unknown) {
  return error instanceof globalThis.Error ? error.message : String(error)
}

function cacheOperation<A, E, R>(effect: Effect.Effect<A, E, R>, operation: string, target: string) {
  return effect.pipe(
    Effect.mapError((error) => new CacheOperationError({ operation, path: target, message: errorMessage(error) })),
  )
}

export * as RepositoryCache from "./repository-cache"
