package agent

import (
	"context"
	"fmt"
	"os"
	"runtime"
	"slices"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"ollie/cmd/olliesrv/internal/backend"
	toolclient "ollie/cmd/olliesrv/internal/toolclient"
	olog "ollie/log"
	"ollie/util"
)

// Agent holds the state of the current Agent entity (the "agent"
// in the traditional sense). It is swappable: when the user runs /agent,
// a new Agent is built from the new agent config while the session
// host remains stable.
type Agent struct {
	history       *History
	runtime       *Runtime
	name          string // display name (defaults to id)
	profile       string // config profile name (e.g. "default")
	agentsDir     string
	systemPrompt  string // system prompt for /agent reloads
	envBlock      string // environment block for /agent reloads
	newToolServer func() *toolclient.ToolsrvConn
	newBackend    func(string) (backend.Backend, error)
	currentAction atomic.Pointer[actionHandle]
	closed        atomic.Bool
	actionMu      sync.Mutex // serializes action registration with shutdown
	warnedContext bool       // true after warning about context window limits
	resultCache   resultCache // per-agent cache of tool results for read-safe tools

	// Execution state — owned by the agent, protected by stateMu.
	state          string              // "idle", "thinking", "calling: <tool>"
	stateSince     time.Time           // when the current state began
	reply          string              // last assistant response
	getCwd         func() string       // returns session working directory
	cwdOverride    string              // per-agent cwd override (empty = inherit session cwd)
	id             string              // agent identity (unique principal)
	parentID       string              // immutable ID of the agent that spawned this agent
	depth          int                 // sub-agent depth (0=top-level, 1=sub-agent, 2=sub-sub-agent)
	activeChildren atomic.Int32        // number of currently-running child sub-agents
	peers         map[string]struct{} // peer agent names (same session)
	peerMu        sync.RWMutex
	fifo          Fifo // prompt queue
	toolCallCount atomic.Int64
	pendingInject  atomic.Pointer[string]
	submitMu       sync.Mutex // serializes Submit calls (commands + turns)
	stateMu        sync.RWMutex
	signalMu       sync.Mutex
	signalCh       chan struct{} // closed on state change; replaced with a fresh channel

	// Event handler — receives events from this agent.
	output            EventHandler
	log               *olog.Logger
	sessionID         string // the owning session's ID
	memoryWakePending atomic.Bool
	save              func()                      // trigger debounced persistence
	flush             func()                      // immediately flush persistence
	onStateChange     func(agentID, state string) // optional callback for state changes
	onProcStart       func(agentID string, pid int, tool, cmd string) // optional callback for proc start
	onClear           func(agentID string)        // optional callback for clear

	// Chat logs — dual format: JSONL for programmatic access, plain text for humans.
	chatMu       sync.RWMutex
	rawLog       []byte        // JSONL format (one Block per line)
	rawStart     int           // byte offset of first byte in rawLog (for truncation accounting)
	textLog      []byte        // Rendered plain text
	textStart    int           // byte offset of first byte in textLog
	chatVers     uint32        // incremented on each append for change detection
	chatCond     *sync.Cond    // signaled on new chat data
	chatSignalMu sync.Mutex
	chatSignalCh chan struct{} // closed on new chat data; replaced with fresh channel
	partialLine  []byte        // current in-flight (partial) block as a JSONL line; never persisted to rawLog
	partialVers  uint64        // bumped whenever partialLine changes, for stream change detection
	plan         []byte        // agent's plan file contents
	blockCounter uint64        // monotonic counter for block ID generation
}

// Backend returns the active backend from the runtime.
func (ag *Agent) Backend() backend.Backend {
	return ag.runtime.Backend
}

// Name returns the agent's display name.
func (ag *Agent) Name() string { return ag.name }

// Profile returns the config profile name (e.g. "default").
func (ag *Agent) Profile() string { return ag.profile }

// Messages returns the conversation history messages.
func (ag *Agent) Messages() []backend.Message {
	if ag.history == nil {
		return nil
	}
	return ag.history.history()
}

// UsageStats holds token usage and cost information.
type UsageStats struct {
	TotalInputTokens         int
	TotalCachedInputTokens   int
	TotalCacheCreationTokens int
	TotalOutputTokens        int
	TotalRequests            int
	Estimated                bool
	LastTurnCostUSD          float64
	SessionCostUSD           float64
	CacheHitRatio            float64
}

// Usage returns the agent's usage statistics.
func (ag *Agent) Usage() *UsageStats {
	if ag.history == nil {
		return nil
	}
	return &UsageStats{
		TotalInputTokens:         ag.history.TotalInputTokens,
		TotalCachedInputTokens:   ag.history.TotalCachedInputTokens,
		TotalCacheCreationTokens: ag.history.TotalCacheCreationTokens,
		TotalOutputTokens:        ag.history.TotalOutputTokens,
		TotalRequests:            ag.history.TotalRequests,
		Estimated:                ag.history.Estimated,
		LastTurnCostUSD:          ag.history.LastTurnCostUSD,
		SessionCostUSD:           ag.history.SessionCostUSD,
		CacheHitRatio:            ag.history.cacheHitRatio(),
	}
}

// SetName changes the agent's display name without reloading config.
func (ag *Agent) SetName(name string) {
	ag.stateMu.Lock()
	ag.name = name
	ag.stateMu.Unlock()
}

// ID returns the agent's unique identity.
func (ag *Agent) ID() string { return ag.id }

// ParentID returns the immutable ID of the agent that spawned this agent.
func (ag *Agent) ParentID() string { return ag.parentID }

// BackendName returns the name of the active backend.
func (ag *Agent) BackendName() string {
	if ag.runtime.Backend == nil {
		return ""
	}
	return ag.runtime.Backend.Name()
}

// ModelName returns the name of the active model.
func (ag *Agent) ModelName() string {
	if ag.runtime.Backend == nil {
		return ""
	}
	return ag.runtime.Backend.Model()
}

// SwitchBackend replaces the active backend by name. The new backend is fully
// constructed before the runtime is changed, so a failed switch leaves the
// current backend usable. Backend changes are only safe between turns.
func (ag *Agent) SwitchBackend(name string) error {
	name = strings.TrimSpace(name)
	if name == "" {
		return fmt.Errorf("backend requires a name")
	}
	if ag.IsRunning() {
		return fmt.Errorf("cannot switch backend while agent is running")
	}
	if ag.newBackend == nil {
		return fmt.Errorf("backend switching unavailable")
	}
	be, err := ag.newBackend(name)
	if err != nil {
		return fmt.Errorf("backend %q: %w", name, err)
	}
	ag.runtime.Backend = be
	ag.save()
	ag.flush()
	ag.notifyChange()
	return nil
}

// SetToolServer updates the tool server connection and factory.
// Used when resuming a paused session that was restored without infra.
func (ag *Agent) SetToolServer(newToolServer func() *toolclient.ToolsrvConn, conn *toolclient.ToolsrvConn) {
	ag.newToolServer = newToolServer
	if ag.runtime != nil {
		ag.runtime.ToolServer = conn
	}
}

// Cwd returns the agent's effective working directory: the per-agent override
// if one is set, otherwise the inherited session working directory.
func (ag *Agent) Cwd() string {
	ag.stateMu.RLock()
	override := ag.cwdOverride
	ag.stateMu.RUnlock()
	if override != "" {
		return override
	}
	if ag.getCwd != nil {
		return ag.getCwd()
	}
	wd, _ := os.Getwd()
	return wd
}

// SessionCwd returns the inherited session working directory, ignoring any
// per-agent override.
func (ag *Agent) SessionCwd() string {
	if ag.getCwd != nil {
		return ag.getCwd()
	}
	wd, _ := os.Getwd()
	return wd
}

// CwdOverride returns the per-agent cwd override, or "" if the agent inherits
// the session working directory.
func (ag *Agent) CwdOverride() string {
	ag.stateMu.RLock()
	defer ag.stateMu.RUnlock()
	return ag.cwdOverride
}

// SetCwdOverride sets (or, with an empty dir, clears) the per-agent working
// directory override and propagates it to the tool server so that this agent's
// tools execute in the chosen directory. Other agents in the session are
// unaffected. The effective directory is also reflected in the preamble
// environment section.
func (ag *Agent) SetCwdOverride(dir string) {
	dir = strings.TrimSpace(dir)
	ag.stateMu.Lock()
	ag.cwdOverride = dir
	ag.stateMu.Unlock()

	// Refresh the preamble environment section to reflect the effective cwd.
	eff := ag.Cwd()
	if ag.runtime != nil {
		ag.envBlock = EnvironmentBlock(eff, runtime.GOOS, util.IsGitRepo(eff), "")
		if ag.runtime.Preamble != nil {
			ag.runtime.Preamble.Set(SectionEnv, ag.envBlock)
		}
	}

	ag.SyncCwdToToolServer()
	ag.notifyChange()
}

// SyncCwdToToolServer pushes this agent's per-agent cwd override to its current
// tool server. The toolsrv keeps per-agent overrides in process memory, so this
// must be re-run whenever the tool server connection is (re)established — on
// profile switch, resume, or respawn — otherwise the agent silently falls back
// to the session cwd. Pushing an empty override clears any stale entry.
func (ag *Agent) SyncCwdToToolServer() {
	ag.stateMu.RLock()
	override := ag.cwdOverride
	ag.stateMu.RUnlock()
	if ts := ag.ToolServer(); ts != nil && ag.id != "" {
		ts.SetAgentCWD(ag.id, override)
	}
}

// SetGetCwd sets the CWD getter callback.
func (ag *Agent) SetGetCwd(fn func() string) {
	ag.getCwd = fn
}

// IsRunning returns true if the agent has an active turn in progress.
func (ag *Agent) IsRunning() bool {
	return ag.currentAction.Load() != nil
}

// Interrupt cancels the current in-progress agent turn.
// Returns true if an action was running and was cancelled.
func (ag *Agent) Interrupt(cause error) bool {
	ag.actionMu.Lock()
	defer ag.actionMu.Unlock()
	if h := ag.currentAction.Load(); h != nil {
		h.cancel(cause)
		return true
	}
	return false
}

// Compact runs manual context compaction. Returns an error if the agent is
// running or compaction fails.
func (ag *Agent) Compact(ctx context.Context) error {
	if ag.IsRunning() {
		return fmt.Errorf("cannot compact while agent is running")
	}
	if ag.history == nil {
		return nil
	}
	ag.SetState("compacting")
	_, err := ag.runCompact(ctx, "manual")
	ag.SetState("idle")
	if err != nil {
		return err
	}
	ag.save()
	return nil
}

// Clear resets the agent history and chat log. Returns an error if the agent is running.
func (ag *Agent) Clear() error {
	if ag.IsRunning() {
		return fmt.Errorf("cannot clear while agent is running")
	}
	ag.history = nil
	ag.chatMu.Lock()
	ag.rawLog = nil
	ag.rawStart = 0
	ag.textLog = nil
	ag.textStart = 0
	ag.partialLine = nil
	ag.partialVers++
	ag.chatVers++
	ag.chatMu.Unlock()
	ag.chatCond.Broadcast()
	if ag.onClear != nil {
		ag.onClear(ag.id)
	}
	return nil
}

// SwitchProfile loads a new agent profile by name, replacing the runtime
// and clearing history. Returns the loaded config on success for the caller
// to reload tools. Returns an error if the agent is running or the profile
// cannot be loaded.
func (ag *Agent) SwitchProfile(name string) (*AgentConfig, error) {
	if ag.IsRunning() {
		return nil, fmt.Errorf("cannot switch agent while agent is running")
	}
	cfgPath := AgentConfigPath(ag.agentsDir, name)
	f, err := os.Open(cfgPath)
	if err != nil {
		return nil, fmt.Errorf("agent %q: %w", name, err)
	}
	cfg, err := Load(f)
	f.Close()
	if err != nil {
		return nil, fmt.Errorf("agent %q: %w", name, err)
	}
	disp := ag.newToolServer()
	if disp != nil && ag.id != "" {
		disp.SetAgentID(ag.id)
	}
	env := []string{"OLLIE_SESSION_ID=" + ag.sessionID, "OLLIE_UNAME=" + ag.id}
	rt := BuildRuntime(cfg, disp, ag.Cwd(), env, ag.systemPrompt, ag.envBlock)
	if cfg.Backend != "" {
		newBe, err := ag.newBackend(cfg.Backend)
		if err != nil {
			return nil, fmt.Errorf("backend %q: %w", cfg.Backend, err)
		}
		if cfg.Model != "" {
			newBe.SetModel(cfg.Model)
		}
		rt.Backend = newBe
	} else {
		rt.Backend = ag.runtime.Backend
		if cfg.Model != "" {
			rt.Backend.SetModel(cfg.Model)
		}
	}
	ag.runtime = rt
	ag.profile = name
	ag.history = nil
	// The profile switch dialed a fresh tool server connection; re-apply the
	// per-agent cwd override so it survives the reconnect.
	ag.SyncCwdToToolServer()
	ag.save()
	ag.flush()
	ag.notifyChange()
	return cfg, nil
}

// Event is a typed output event emitted during an agent turn or in response
// to a command.
// Event carries a single piece of output from the agent loop to consumers
// (frontends, loggers, the turn orchestrator in turn.go).
//
// The Role field determines the event semantics:
//
//	Role          Name       Content                     Emitted by
//	────────────  ─────────  ──────────────────────────  ──────────
//	"user"        —          user input text             turn.go (before run)
//	"assistant"   —          streamed LLM text chunk     loop.go (streamResponse)
//	"reasoning"   —          <think>…</think> chunks    loop.go (streamResponse)
//	"call"        tool name  JSON args                   loop.go (execOne)
//	"tool"        tool name  result text (may stream)    loop.go (execOne)
//	"usage"       —          "in out est cost cached creation" loop.go (streamResponse)
//	"state"       —          "thinking"|"compacting"|…   loop.go / turn.go
//	"limitretry"  —          —                           loop.go (rate limit hit)
//	"retry"       —          "HH:MM:SS" countdown       loop.go (retryCountdown)
//	"maxsteps"    —          step count as string        loop.go (budget exhausted)
//	"error"       —          error message               turn.go / loop.go
//	"info"        —          informational text          turn.go (compaction, cost)
//
// turn.go intercepts events before forwarding to the external handler:
//   - "assistant" → accumulates reply text
//   - "call"      → updates agent state to "calling: <name>"
//   - "tool"      → logs result
//   - "state"     → calls ag.SetState()
//   - "limitretry"→ sets state to "limitretry"
//   - "usage"     → parses token counts, updates history
//   - "error"     → logs
type Event struct {
	Role         string
	Name         string
	Content      string
	ResponseID   string
	OutputFormat string
}

// EventHandler receives events from the agent.
type EventHandler func(Event)

// actionHandle holds the cancel function for the current agent turn.
type actionHandle struct {
	cancel context.CancelCauseFunc
	done   chan struct{}
}

// SetSessionEnv injects session env vars into the execute server.
func (ag *Agent) SetSessionEnv(sessionID string) {
	if ag.runtime == nil || ag.runtime.ToolServer == nil {
		return
	}
	ag.runtime.ToolServer.SetEnv("OLLIE_SESSION_ID", sessionID)
	if ag.id != "" {
		ag.runtime.ToolServer.SetAgentID(ag.id)
	}
	if u := os.Getenv("USER"); u != "" {
		ag.runtime.ToolServer.SetEnv("USER", u)
	}
}

// SetEnv stores an environment variable on the execute server.
func (ag *Agent) SetEnv(key, value string) {
	ag.runtime.ToolServer.SetEnv(key, value)
}

// Close releases agent resources (dispatcher, execute server). It first prevents
// new work, cancels the active turn, and waits for that turn to release its
// references to the runtime before closing the tools connection.
func (ag *Agent) Close() {
	ag.closed.Store(true)

	ag.actionMu.Lock()
	h := ag.currentAction.Load()
	if h != nil {
		h.cancel(context.Canceled)
	}
	ag.actionMu.Unlock()
	if h != nil {
		<-h.done
	}

	if ag.runtime != nil && ag.runtime.ToolServer != nil {
		ag.runtime.ToolServer.Close()
	}
}

// SetCWD updates the preamble environment section and toolserver CWD.
// Note: This updates local state only. To change session CWD, use session.SetCwd().
func (ag *Agent) SetCWD(dir string) {
	isGitRepo := util.IsGitRepo(dir)
	ag.envBlock = EnvironmentBlock(dir, runtime.GOOS, isGitRepo, "")
	ag.runtime.Preamble.Set(SectionEnv, ag.envBlock)
	if ag.runtime.ToolServer != nil {
		ag.runtime.ToolServer.SetCWD(dir)
	}
	ag.notifyChange()
}

// RefreshTools forces a refresh of the tool listing in the agent's preamble.
func (ag *Agent) RefreshTools() {
	if infos, err := ag.runtime.ToolServer.ListTools(); err == nil {
		ag.runtime.Preamble.Set(SectionTools, RenderTools(infos))
	}
}

// SetToolsPreamble updates the tools section of the preamble.
func (ag *Agent) SetToolsPreamble(content string) {
	ag.runtime.Preamble.Set(SectionTools, content)
}

// CtxSz returns a human-readable context size string.
func (ag *Agent) CtxSz() string {
	if ag.history == nil {
		return "no active session"
	}
	ctxLen := ag.runtime.Backend.ContextLength(context.Background())
	if ctxLen <= 0 {
		ctxLen = defaultContextLength
	}
	estimated := ag.history.estimateTokens()
	pct := estimated * 100 / ctxLen
	return fmt.Sprintf("%d / %d (%d%%)", estimated, ctxLen, pct)
}

// CostStr returns formatted cost information.
func (ag *Agent) CostStr() string {
	if ag.history == nil {
		return "no active session"
	}
	return fmt.Sprintf("costLast=$%.4f\ncostSession=$%.4f\n",
		ag.history.LastTurnCostUSD, ag.history.SessionCostUSD)
}

// UsageStr returns formatted usage information.
func (ag *Agent) UsageStr() string {
	if ag.history == nil {
		return "no active session"
	}
	str := fmt.Sprintf("%d in, %d out, %d requests",
		ag.history.TotalInputTokens, ag.history.TotalOutputTokens,
		ag.history.TotalRequests)
	if ag.history.TotalCachedInputTokens > 0 {
		str += fmt.Sprintf(", %d cached", ag.history.TotalCachedInputTokens)
	}
	if ag.history.Estimated {
		str += " [estimated]"
	}
	return str
}

// Context returns the full message context (system prompt + history).
func (ag *Agent) Context() []backend.Message {
	var msgs []backend.Message
	if ag.history != nil {
		msgs = slices.Clone(ag.history.history())
	}
	if preamble := ag.runtime.PreambleString(); preamble != "" {
		msgs = append([]backend.Message{{Role: "system", Content: preamble}}, msgs...)
	}
	return msgs
}

// SystemPrompt returns the rendered system prompt.
func (ag *Agent) SystemPrompt() string {
	return ag.runtime.PreambleString()
}

// GenParams returns the current generation parameters.
func (ag *Agent) GenParams() backend.GenerationParams {
	return ag.runtime.GenParams
}

// SetGenParams sets the generation parameters.
func (ag *Agent) SetGenParams(params backend.GenerationParams) {
	ag.runtime.GenParams = params
}

// ListModels returns available models from the backend.
func (ag *Agent) ListModels() []string {
	return ag.runtime.Backend.Models(context.Background())
}

// ToolServer returns the tool execution server, or nil if unavailable.
// Exported for use by the 9P filesystem layer to sync tool registries.
func (ag *Agent) ToolServer() *toolclient.ToolsrvConn {
	return ag.runtime.ToolServer
}

// SetRuntime replaces the agent's runtime (used on session resume).
func (ag *Agent) SetRuntime(rt *Runtime) {
	ag.runtime = rt
}

// SetCompactionModel sets the model used for context compaction.
func (ag *Agent) SetCompactionModel(model string) {
	ag.runtime.CompactionModel = model
}

// CompactionModel returns the configured context compaction model.
func (ag *Agent) CompactionModel() string {
	return ag.runtime.CompactionModel
}

// Queue pushes a prompt onto the agent's FIFO.
func (ag *Agent) Queue(prompt string) error {
	return ag.fifo.Push(prompt)
}

// RequireMemoryWake makes the next top-level turn load persistent memory first.
func (ag *Agent) RequireMemoryWake() {
	if ag.depth == 0 {
		ag.memoryWakePending.Store(true)
	}
}

func (ag *Agent) consumeMemoryWake() bool {
	return ag.memoryWakePending.CompareAndSwap(true, false)
}

// PopQueue pops the next prompt from the FIFO.
func (ag *Agent) PopQueue() (string, bool) {
	return ag.fifo.Pop()
}

// AgentParams holds the runtime dependencies for constructing a new Agent.
// Not to be confused with AgentConfig, which is the on-disk JSON schema.
type AgentParams struct {
	ID            string // unique agent identity (uname)
	SessionID     string // id of session the agent belongs to
	Profile       string // config profile name (e.g. "default" → agents/default.json)
	ParentID      string // immutable ID of the agent that spawned this agent
	History       *History
	Runtime       *Runtime
	AgentsDir     string
	GetCwd        func() string // returns session working directory
	SystemPrompt  string
	EnvBlock      string
	NewToolServer func() *toolclient.ToolsrvConn
	NewBackend    func(string) (backend.Backend, error)
	Log           *olog.Logger
	Save          func()
	Flush         func()
}

// NewAgent constructs an Agent from the given configuration.
// Post-construction wiring (SetSessionEnv) is handled internally —
// no additional calls are required after construction.
func NewAgent(cfg AgentParams) *Agent {
	ag := &Agent{
		history:         cfg.History,
		runtime:         cfg.Runtime,
		profile:         cfg.Profile,
		name:            cfg.ID, // display name defaults to uname
		agentsDir:       cfg.AgentsDir,
		id:              cfg.ID,
		parentID:        cfg.ParentID,
		getCwd:          cfg.GetCwd,
		systemPrompt:  cfg.SystemPrompt,
		envBlock:      cfg.EnvBlock,
		newToolServer: cfg.NewToolServer,
		newBackend:    cfg.NewBackend,
		log:           cfg.Log,
		sessionID:     cfg.SessionID,
		save:          cfg.Save,
		flush:         cfg.Flush,
		state:         "idle",
	}
	ag.signalCh = make(chan struct{})
	ag.chatSignalCh = make(chan struct{})
	ag.chatCond = sync.NewCond(ag.chatMu.RLocker())
	ag.initChatHandler()
	ag.SetSessionEnv(cfg.SessionID)
	return ag
}