import { resolveOpenCodeDataDirectory } from './opencode-data-directory'
import {
  bindOpenCodeSession,
  type OpenCodeSessionBinding
} from '../../shared/agent-hook-listener/opencode-session-registry'
import {
  correlateOpenCodeSessionOwners,
  type CorrelatedClient,
  type CorrelatedPane,
  type CorrelatedSession,
  type SessionOwnership
} from '../../shared/agent-hook-listener/opencode-session-correlation'
import type {
  BinderSessionRow,
  OpenCodeSessionCursor
} from '../foreign-sqlite-readers/opencode-binder-sessions-result'
import { splitWorktreeIdForFilesystem } from '../../shared/worktree/id'
import { listRegisteredPtys } from '../memory/pty-registry'
import { isOpenCodeClientProcess, type ProcessIdentityRow } from './opencode-client-sweep'
import type { HookListenerState } from '../../shared/agent-hook-listener/listener-state'

/**
 * Main-process binder feeding the session→pane registry (#21359), for OpenCode 1
 * `serve` + `attach` only (see isOpenCodeSharedServerPost).
 *
 * Each round: read new sessions from the shared server's SQLite store,
 * snapshot panes, sweep for live clients, correlate, bind. Everything the
 * round needs is injected so the decision core stays unit-testable; the
 * store read runs on the foreign SQLite reader worker
 * (foreign-sqlite-readers/readers/opencode-binder-sessions.ts).
 */

/** One pane snapshot feeding a binder round. */
export type BinderPaneSnapshot = {
  paneKey: string
  /** Worktree root backing the pane (null when unknown); sessions beneath it are candidates. */
  directory: string | null
  worktreeId: string | null
  shellPid: number | null
}

/** Everything one binder round needs, injected for tests. */
export type BinderRoundDeps = {
  nowMs: number
  sessions: readonly BinderSessionRow[]
  panes: readonly BinderPaneSnapshot[]
  processes: readonly ProcessIdentityRow[]
  knownOwners: ReadonlyMap<string, string>
  parentBySessionId: ReadonlyMap<string, string | null>
}

/** Ownership decisions from one binder round. */
export type BinderRoundResult = {
  ownerships: SessionOwnership[]
}

/** Cursor before anything was ever read. */
export const OPENCODE_SESSION_CURSOR_START: OpenCodeSessionCursor = { ms: 0, id: '' }

/** Order cursors the way the store lists rows: oldest first, id as tiebreak. */
function compareSessionRows(left: OpenCodeSessionCursor, right: OpenCodeSessionCursor): number {
  return left.ms - right.ms || (left.id < right.id ? -1 : left.id > right.id ? 1 : 0)
}

/**
 * Advance the store cursor past handled rows only. `fresh` arrives in store
 * order; handling is prefix-closed (the unbound-cap break only ever skips the
 * tail), so the first unhandled row freezes the cursor and every row at or
 * past it is re-listed next round instead of silently dropped.
 */
export function advanceBinderCursor(args: {
  fresh: readonly BinderSessionRow[]
  isHandled: (sessionId: string) => boolean
  current: OpenCodeSessionCursor
}): OpenCodeSessionCursor {
  let cursor = args.current
  for (const session of args.fresh) {
    if (!args.isHandled(session.id)) {
      break
    }
    const candidate: OpenCodeSessionCursor = { ms: session.createdAtMs, id: session.id }
    if (compareSessionRows(candidate, cursor) > 0) {
      cursor = candidate
    }
  }
  return cursor
}

/** pid→ppid index for one sweep; first row wins on duplicate pids. */
function childrenIndex(processes: readonly ProcessIdentityRow[]): Map<number, number> {
  const ppidByPid = new Map<number, number>()
  for (const row of processes) {
    if (!ppidByPid.has(row.pid)) {
      ppidByPid.set(row.pid, row.ppid)
    }
  }
  return ppidByPid
}

/** Nearest pane shell at or above this pid; external terminals stay unattributed. */
function owningPane(
  ppidByPid: Map<number, number>,
  shellPidByPid: Map<number, string>,
  pid: number
): string | null {
  const seen = new Set<number>()
  let current: number | undefined = pid
  while (current !== undefined && !seen.has(current)) {
    seen.add(current)
    const owner = shellPidByPid.get(current)
    if (owner) {
      return owner
    }
    current = ppidByPid.get(current)
  }
  return null
}

/** Attribute opencode client rows to panes via shell-subtree walks. */
function toCorrelatedClients(
  processes: readonly ProcessIdentityRow[],
  panes: readonly BinderPaneSnapshot[],
  nowMs: number
): CorrelatedClient[] {
  const ppidByPid = childrenIndex(processes)
  const shellPidByPid = new Map<number, string>()
  for (const pane of panes) {
    if (pane.shellPid !== null && !shellPidByPid.has(pane.shellPid)) {
      shellPidByPid.set(pane.shellPid, pane.paneKey)
    }
  }
  const clients: CorrelatedClient[] = []
  for (const row of processes) {
    if (!isOpenCodeClientProcess(row)) {
      continue
    }
    const paneKey = owningPane(ppidByPid, shellPidByPid, row.pid)
    if (!paneKey) {
      continue
    }
    // Why lastSeenAlive = now: the sweep just observed it. Bracketing uses
    // startedAt for the lower bound and this observation for the upper.
    clients.push({ paneKey, startedAtMs: row.startedAtMs, lastSeenAliveMs: nowMs, argv: row.argv })
  }
  return clients
}

/** Pure round core: correlate unbound sessions against panes and clients. */
export function runOpenCodeBinderRound(deps: BinderRoundDeps): BinderRoundResult {
  // Why dedupe by key, newest wins: remints and reattachments can leave a
  // stale registry row beside the live one; counting rows instead of panes
  // would turn every same-pane tie into a false ambiguous and nothing would
  // ever bind, while the oldest row would point the candidate set at a dead
  // worktree.
  const paneByKey = new Map<string, CorrelatedPane>()
  for (const pane of deps.panes) {
    paneByKey.set(pane.paneKey, { paneKey: pane.paneKey, directory: pane.directory })
  }
  const panes = [...paneByKey.values()]
  const clients = toCorrelatedClients(deps.processes, deps.panes, deps.nowMs)
  const sessions: CorrelatedSession[] = deps.sessions.map((row) => ({
    id: row.id,
    directory: row.directory,
    createdAtMs: row.createdAtMs,
    parentId: row.parentId
  }))
  // Why resolve inheritance here: the SQLite round only carries new rows, so
  // an old root is invisible to the correlator; the binder's parent map walks
  // the chain and the registry supplies the known root owner. Resolved heirs
  // are emitted as binds (the registry lacks them) and fed back as known so
  // the correlator skips what is already decided.
  const knownOwners = new Map(deps.knownOwners)
  const inherited: SessionOwnership[] = []
  for (const session of sessions) {
    if (knownOwners.has(session.id) || !session.parentId) {
      continue
    }
    let parent: string | null | undefined = session.parentId
    const seen = new Set<string>([session.id])
    while (parent && !seen.has(parent)) {
      seen.add(parent)
      const owner = knownOwners.get(parent)
      if (owner) {
        knownOwners.set(session.id, owner)
        inherited.push({ sessionId: session.id, paneKey: owner, basis: 'creation-correlation' })
        break
      }
      parent = deps.parentBySessionId.get(parent)
    }
  }
  const ownerships = [
    ...inherited,
    ...correlateOpenCodeSessionOwners({
      sessions,
      panes,
      clients,
      knownOwners
    })
  ]
  return { ownerships }
}

/** Default database path for the local shared server. */
export function defaultOpenCodeDbPath(): string {
  return `${resolveOpenCodeDataDirectory()}/opencode.db`
}

/**
 * Live local panes from the PTY registry: pane key, worktree root and shell
 * pid. Panes without a key or pid (hydrated gaps, remote panes) cannot own a
 * client subtree, so they are skipped — their sessions stay unbound rather
 * than guessed.
 */
export function listBinderPaneSnapshots(): BinderPaneSnapshot[] {
  const snapshots: BinderPaneSnapshot[] = []
  for (const pty of listRegisteredPtys()) {
    if (!pty.paneKey || pty.pid === null) {
      continue
    }
    const parsed = pty.worktreeId ? splitWorktreeIdForFilesystem(pty.worktreeId) : null
    snapshots.push({
      paneKey: pty.paneKey,
      directory: parsed?.worktreePath ?? null,
      worktreeId: pty.worktreeId,
      shellPid: pty.pid
    })
  }
  return snapshots
}

/** Apply one round's decisions to the listener registry. */
export function applyBinderOwnerships(
  state: HookListenerState,
  panes: readonly BinderPaneSnapshot[],
  ownerships: readonly SessionOwnership[],
  nowMs: number
): number {
  const worktreeByPane = new Map<string, string | null>()
  for (const pane of panes) {
    // Why overwrite: matching the round's newest-wins pane dedupe, so a
    // remint's live row wins over a stale row with a different worktree.
    worktreeByPane.set(pane.paneKey, pane.worktreeId)
  }
  let applied = 0
  for (const ownership of ownerships) {
    const binding: OpenCodeSessionBinding = {
      paneKey: ownership.paneKey,
      boundAt: nowMs,
      basis: ownership.basis
    }
    const worktreeId = worktreeByPane.get(ownership.paneKey)
    if (worktreeId) {
      binding.worktreeId = worktreeId
    }
    if (bindOpenCodeSession(state, ownership.sessionId, binding)) {
      applied += 1
    }
  }
  return applied
}