import type { AgentState, Metadata, Session, TodoItem, WorktreeMetadata } from './schemas'
import { isKnownFlavor } from './flavors'
import type { AgentFlavor } from './modes'

export type PendingRequestKind = 'permission' | 'input'

const INPUT_REQUEST_TOOLS = new Set([
    'AskUserQuestion',
    'ask_user_question',
    'ExitPlanMode',
    'exit_plan_mode',
    'request_user_input'
])

/** Cap on `pendingRequests` carried in `SessionSummary`. The list is meant for
 *  per-row hover copy ("Approve `Bash`, `Edit` (+1 more)"); deep inspection
 *  should use `Session.agentState.requests`. The `pendingRequestsCount` field
 *  is the authoritative total — `pendingRequests.length` may be smaller. */
export const PENDING_REQUEST_SUMMARY_CAP = 5

export type PendingRequest = {
    id: string
    kind: PendingRequestKind
    tool: string
    /** Epoch ms when the request was raised; falls back to the caller-supplied
     *  `fallbackSince` (typically `session.updatedAt`) for older requests
     *  stored without `createdAt`. */
    since: number
}

function classifyKind(tool: string): PendingRequestKind {
    return INPUT_REQUEST_TOOLS.has(tool) ? 'input' : 'permission'
}

export type SessionSummaryMetadata = {
    name?: string
    path: string
    machineId?: string
    summary?: { text: string }
    flavor?: string | null
    worktree?: WorktreeMetadata
    agentSessionId?: string
    lifecycleState?: string
    /** Loopback MCP URL when session CLI happy server is running (#956). */
    hapiMcpUrl?: string
}

export type SessionSummary = {
    hasConversationContent?: boolean
    id: string
    active: boolean
    thinking: boolean
    activeAt: number
    updatedAt: number
    /** Epoch ms when the session was created. Drives the fixed-order session
     *  list sort. Optional because summaries from an older hub lack it —
     *  consumers fall back to `updatedAt` via the session-order key. */
    createdAt?: number
    pinned?: boolean
    globalPinned?: boolean
    metadata: SessionSummaryMetadata | null
    /** Watermarks for structured SSE patches (PR #897). List cache must gate
     *  without requiring a detail query — otherwise global SSE forces O(N)
     *  /sessions invalidation for every versioned write. */
    metadataVersion: number
    agentStateVersion: number
    todosUpdatedAt: number
    todoProgress: { completed: number; total: number } | null
    pendingRequestsCount: number
    pendingRequestKinds: PendingRequestKind[]
    /** Capped, oldest-first slice of pending tool requests. Use this for tooltip
     *  / per-row UX. The full count (which may exceed the cap) is in
     *  `pendingRequestsCount`. */
    pendingRequests: PendingRequest[]
    backgroundTaskCount: number
    futureScheduledMessageCount: number
    /** Epoch ms of the soonest uninvoked future scheduled message, or null. */
    nextScheduledAt: number | null
    model: string | null
    modelReasoningEffort?: string | null
    effort: string | null
}

// Re-exported as a standalone derivation so SSE patch handlers can recompute
// summary fields from a structured `agentState` patch without needing the
// full Session in hand.
export function computePendingRequestKinds(agentState: AgentState | null | undefined): PendingRequestKind[] {
    const requests = agentState?.requests
    if (!requests) {
        return []
    }

    const kinds = new Set<PendingRequestKind>()
    for (const request of Object.values(requests)) {
        kinds.add(classifyKind(request.tool))
    }

    return kinds.has('permission') && kinds.has('input')
        ? ['permission', 'input']
        : Array.from(kinds)
}

export function computePendingRequests(
    agentState: AgentState | null | undefined,
    fallbackSince: number,
    cap: number = PENDING_REQUEST_SUMMARY_CAP
): PendingRequest[] {
    const requests = agentState?.requests
    if (!requests) {
        return []
    }

    const items: PendingRequest[] = []
    for (const [id, request] of Object.entries(requests)) {
        items.push({
            id,
            kind: classifyKind(request.tool),
            tool: request.tool,
            since: typeof request.createdAt === 'number' ? request.createdAt : fallbackSince
        })
    }

    items.sort((a, b) => {
        if (a.since !== b.since) return a.since - b.since
        return a.id < b.id ? -1 : a.id > b.id ? 1 : 0
    })

    return cap >= items.length ? items : items.slice(0, cap)
}

export function getPendingRequestKinds(session: Session): PendingRequestKind[] {
    return computePendingRequestKinds(session.agentState)
}

export function getPendingRequests(
    session: Session,
    cap: number = PENDING_REQUEST_SUMMARY_CAP
): PendingRequest[] {
    return computePendingRequests(session.agentState, session.updatedAt, cap)
}

export function computePendingRequestsCount(agentState: AgentState | null | undefined): number {
    return agentState?.requests ? Object.keys(agentState.requests).length : 0
}

export function computeTodoProgress(todos: TodoItem[] | undefined): SessionSummary['todoProgress'] {
    if (!todos?.length) {
        return null
    }
    return {
        completed: todos.filter((todo) => todo.status === 'completed').length,
        total: todos.length
    }
}

const AGENT_SESSION_ID_FIELD_BY_FLAVOR: Partial<Record<AgentFlavor, keyof Metadata>> = {
    claude: 'claudeSessionId',
    codex: 'codexSessionId',
    gemini: 'geminiSessionId',
    opencode: 'opencodeSessionId',
    grok: 'grokSessionId',
    agy: 'agySessionId',
    cursor: 'cursorSessionId',
    kimi: 'kimiSessionId',
    copilot: 'copilotSessionId',
    pi: 'piSessionId'
}

function getSummaryAgentSessionId(metadata: Metadata): string | undefined {
    const flavor = metadata.flavor
    if (isKnownFlavor(flavor)) {
        const flavorField = AGENT_SESSION_ID_FIELD_BY_FLAVOR[flavor]
        if (!flavorField) return undefined
        const flavorSessionId = metadata[flavorField]
        return typeof flavorSessionId === 'string' && flavorSessionId.trim()
            ? flavorSessionId.trim()
            : undefined
    }

    // Legacy fallback only applies when the stored flavor is missing or unknown.
    return metadata.codexSessionId
        ?? metadata.claudeSessionId
        ?? metadata.geminiSessionId
        ?? metadata.opencodeSessionId
        ?? metadata.grokSessionId
        ?? metadata.agySessionId
        ?? metadata.cursorSessionId
        ?? metadata.kimiSessionId
        ?? metadata.copilotSessionId
        ?? undefined
}

export function toSessionSummaryMetadata(metadata: Metadata | null | undefined): SessionSummaryMetadata | null {
    if (!metadata) {
        return null
    }
    return {
        name: metadata.name,
        path: metadata.path,
        machineId: metadata.machineId ?? undefined,
        summary: metadata.summary ? { text: metadata.summary.text } : undefined,
        flavor: metadata.flavor ?? null,
        worktree: metadata.worktree,
        agentSessionId: getSummaryAgentSessionId(metadata),
        lifecycleState: metadata.lifecycleState,
        hapiMcpUrl: metadata.hapiMcpUrl ?? undefined
    }
}

export function toSessionSummary(session: Session): SessionSummary {
    return {
        hasConversationContent: session.hasConversationContent ?? false,
        id: session.id,
        active: session.active,
        thinking: session.thinking,
        activeAt: session.activeAt,
        updatedAt: session.updatedAt,
        createdAt: session.createdAt,
        pinned: session.pinned ?? false,
        globalPinned: session.globalPinned ?? false,
        metadata: toSessionSummaryMetadata(session.metadata),
        metadataVersion: session.metadataVersion,
        agentStateVersion: session.agentStateVersion,
        todosUpdatedAt: session.todosUpdatedAt ?? 0,
        todoProgress: computeTodoProgress(session.todos),
        pendingRequestsCount: computePendingRequestsCount(session.agentState),
        pendingRequestKinds: computePendingRequestKinds(session.agentState),
        pendingRequests: computePendingRequests(session.agentState, session.updatedAt),
        backgroundTaskCount: session.backgroundTaskCount ?? 0,
        futureScheduledMessageCount: 0,
        nextScheduledAt: null,
        model: session.model,
        modelReasoningEffort: session.modelReasoningEffort,
        effort: session.effort
    }
}