import { Message, Model, Part, Session, SnapshotFileDiff } from "@opencode-ai/sdk/v2"
import { fn } from "@opencode-ai/core/util/fn"
import { iife } from "@opencode-ai/core/util/iife"
import z from "zod"
import { Storage } from "./storage"

export namespace Share {
  export const Info = z.object({
    id: z.string(),
    secret: z.string(),
    sessionID: z.string(),
  })
  export type Info = z.infer<typeof Info>

  export const Data = z.discriminatedUnion("type", [
    z.object({
      type: z.literal("session"),
      data: z.custom<Session>(),
    }),
    z.object({
      type: z.literal("message"),
      data: z.custom<Message>(),
    }),
    z.object({
      type: z.literal("part"),
      data: z.custom<Part>(),
    }),
    z.object({
      type: z.literal("session_diff"),
      data: z.custom<SnapshotFileDiff[]>(),
    }),
    z.object({
      type: z.literal("model"),
      data: z.custom<Model[]>(),
    }),
  ])
  export type Data = z.infer<typeof Data>

  type Snapshot = {
    data: Data[]
  }

  type Compaction = {
    event?: string
    data: Data[]
  }

  function key(item: Data) {
    switch (item.type) {
      case "session":
        return "session"
      case "message":
        return `message/${item.data.id}`
      case "part":
        return `part/${item.data.messageID}/${item.data.id}`
      case "session_diff":
        return "session_diff"
      case "model":
        return "model"
    }
  }

  function merge(...items: Data[][]) {
    const map = new Map<string, Data>()
    for (const list of items) {
      for (const item of list) {
        map.set(key(item), item)
      }
    }
    return Array.from(map.entries())
      .sort(([a], [b]) => a.localeCompare(b))
      .map(([, item]) => item)
  }

  async function readSnapshot(shareID: string) {
    return (await Storage.read<Snapshot>(["share_snapshot", shareID]))?.data
  }

  async function writeSnapshot(shareID: string, data: Data[]) {
    await Storage.write<Snapshot>(["share_snapshot", shareID], { data })
  }

  async function legacy(shareID: string) {
    const compaction: Compaction = (await Storage.read<Compaction>(["share_compaction", shareID])) ?? {
      data: [],
      event: undefined,
    }
    const list = await Storage.list({
      prefix: ["share_event", shareID],
      before: compaction.event,
    }).then((x) => x.toReversed())
    if (list.length === 0) {
      if (compaction.data.length > 0) await writeSnapshot(shareID, compaction.data)
      return compaction.data
    }

    const next = merge(
      compaction.data,
      await Promise.all(list.map(async (event) => await Storage.read<Data[]>(event))).then((x) =>
        x.flatMap((item) => item ?? []),
      ),
    )

    await Promise.all([
      Storage.write(["share_compaction", shareID], {
        event: list.at(-1)?.at(-1),
        data: next,
      }),
      writeSnapshot(shareID, next),
    ])
    return next
  }

  export const create = fn(z.object({ sessionID: z.string() }), async (body) => {
    const isTest = process.env.NODE_ENV === "test" || body.sessionID.startsWith("test_")
    const info: Info = {
      id: (isTest ? "test_" : "") + body.sessionID.slice(-8),
      sessionID: body.sessionID,
      secret: crypto.randomUUID(),
    }
    const exists = await get(info.id)
    if (exists) throw new Errors.AlreadyExists(info.id)
    await Promise.all([Storage.write(["share", info.id], info), writeSnapshot(info.id, [])])
    return info
  })

  export async function get(id: string) {
    return Storage.read<Info>(["share", id])
  }

  export const remove = fn(Info.pick({ id: true, secret: true }), async (body) => {
    const share = await get(body.id)
    if (!share) throw new Errors.NotFound(body.id)
    if (share.secret !== body.secret) throw new Errors.InvalidSecret(body.id)
    await Storage.remove(["share", body.id])
    const groups = await Promise.all([
      Storage.list({ prefix: ["share_snapshot", body.id] }),
      Storage.list({ prefix: ["share_compaction", body.id] }),
      Storage.list({ prefix: ["share_event", body.id] }),
      Storage.list({ prefix: ["share_data", body.id] }),
    ])
    for (const item of groups.flat()) {
      await Storage.remove(item)
    }
  })

  export const sync = fn(
    z.object({
      share: Info.pick({ id: true, secret: true }),
      data: Data.array(),
    }),
    async (input) => {
      const share = await get(input.share.id)
      if (!share) throw new Errors.NotFound(input.share.id)
      if (share.secret !== input.share.secret) throw new Errors.InvalidSecret(input.share.id)
      const data = (await readSnapshot(input.share.id)) ?? (await legacy(input.share.id))
      await writeSnapshot(input.share.id, merge(data, input.data))
    },
  )

  export async function data(shareID: string) {
    return (await readSnapshot(shareID)) ?? legacy(shareID)
  }

  export const syncOld = fn(
    z.object({
      share: Info.pick({ id: true, secret: true }),
      data: Data.array(),
    }),
    async (input) => {
      const share = await get(input.share.id)
      if (!share) throw new Errors.NotFound(input.share.id)
      if (share.secret !== input.share.secret) throw new Errors.InvalidSecret(input.share.id)
      const promises = []
      for (const item of input.data) {
        promises.push(
          iife(async () => {
            switch (item.type) {
              case "session":
                await Storage.write(["share_data", input.share.id, "session"], item.data)
                break
              case "message": {
                const data = item.data as Message
                await Storage.write(["share_data", input.share.id, "message", data.id], item.data)
                break
              }
              case "part": {
                const data = item.data as Part
                await Storage.write(["share_data", input.share.id, "part", data.messageID, data.id], item.data)
                break
              }
              case "session_diff":
                await Storage.write(["share_data", input.share.id, "session_diff"], item.data)
                break
              case "model":
                await Storage.write(["share_data", input.share.id, "model"], item.data)
                break
            }
          }),
        )
      }
      await Promise.all(promises)
    },
  )

  export const Errors = {
    NotFound: class extends Error {
      constructor(public id: string) {
        super(`Share not found: ${id}`)
      }
    },
    InvalidSecret: class extends Error {
      constructor(public id: string) {
        super(`Share secret invalid: ${id}`)
      }
    },
    AlreadyExists: class extends Error {
      constructor(public id: string) {
        super(`Share already exists: ${id}`)
      }
    },
  }
}
