package fs

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"strings"
	"sync"

	"ollie/cmd/olliesrv/internal/agent"
	"ollie/cmd/olliesrv/internal/backend"
	"ollie/cmd/olliesrv/internal/bypass"
	"ollie/virtfs"
	"ollie/cmd/olliesrv/internal/session"
	"ollie/toolsrv"
)

// mergeCtx returns a context that cancels when either parent or child cancels.
// parent is typically the session context; child is the per-read timeout from the server.
func mergeCtx(parent, child context.Context) (context.Context, context.CancelFunc) {
	merged, cancel := context.WithCancel(parent)
	stop := context.AfterFunc(child, func() { cancel() })
	return merged, func() { stop(); cancel() }
}

// wireAgentEvents connects an agent's output and state change events.
// Called once per agent: at creation (handlers_agent.go) and on restore (newroot.go).
//
// Contract:
//   - SetOutput → events flow to the AgentLog (chat stream, tool blocks, etc.)
//   - SetOnStateChange → state transitions publish to the event bus
func wireAgentEvents(sessID string, ag *agent.Agent, al *AgentLog) {
	ag.SetOutput(NewEventHandler(al))
	ag.SetOnStateChange(func(agentID, state string) {
		session.PublishEvent("session."+sessID+".agent."+agentID+".state", state)
	})
}

func readBackends() ([]byte, error) {
	return []byte(strings.Join(backend.Backends(), "\n") + "\n"), nil
}

var helpFn func() string

// helpSpec stores the spec for help generation. Set during tree build.
var helpSpec *virtfs.FsNodeDecl

func readHelp() ([]byte, error) {
	if helpFn == nil {
		return []byte("help not initialized\n"), nil
	}
	return []byte(helpFn()), nil
}

func init() {
	helpFn = func() string {
		helpOnce.Do(func() {
			if helpSpec != nil {
				helpText = virtfs.GenerateHelp(*helpSpec)
			}
		})
		return helpText
	}
}

var (
	helpOnce sync.Once
	helpText string
)

func readModels(mc *ModelCache) ([]byte, error) {
	if mc != nil {
		return mc.Get(), nil
	}
	return []byte("(no model cache)\n"), nil
}

func readAgents() ([]byte, error) {
	var sb strings.Builder
	for _, dir := range agent.AgentsDirs() {
		entries, err := os.ReadDir(dir)
		if err != nil {
			continue
		}
		for _, e := range entries {
			if !e.IsDir() && strings.HasSuffix(e.Name(), ".json") {
				sb.WriteString(strings.TrimSuffix(e.Name(), ".json"))
				sb.WriteByte('\n')
			}
		}
	}
	return []byte(sb.String()), nil
}

func readTools() ([]byte, error) {
	tools := toolsrv.DiscoverTools()
	if len(tools) == 0 {
		return []byte("(no tools found)\n"), nil
	}
	var sb strings.Builder
	for _, ti := range tools {
		fmt.Fprintf(&sb, "%-24s %s\n", ti.Name, ti.Description)
	}
	return []byte(sb.String()), nil
}

func rootCtlHandler(mc *ModelCache, invalidate func(), shutdown func()) func([]byte) ([]byte, error) {
	handlers := map[string]func([]string) ([]byte, error){
		"invalidate": func(_ []string) ([]byte, error) {
			if mc != nil {
				mc.Invalidate()
			}
			if invalidate != nil {
				invalidate()
			}
			return []byte("ok\n"), nil
		},
		"kill": func(_ []string) ([]byte, error) {
			if shutdown != nil {
				shutdown()
			}
			return []byte("ok\n"), nil
		},
	}
	return func(data []byte) ([]byte, error) {
		return dispatch(handlers, data)
	}
}

func readEventwait() ([]byte, error) {
	return nil, fmt.Errorf("eventwait: use blocking read")
}

func blockEventwait(cctx context.Context, _ string) ([]byte, string, error) {
	return session.WaitEvent(cctx)
}

func requestGenerate(ctx context.Context, data []byte) ([]byte, error) {
	var req backend.GenerateRequest
	if err := json.Unmarshal(data, &req); err != nil {
		req.Prompt = strings.TrimSpace(string(data))
	}
	result, err := backend.Generate(ctx, req)
	if err != nil {
		return nil, err
	}
	return []byte(result + "\n"), nil
}

func readAliases() ([]byte, error) {
	var sb strings.Builder
	for name, sess := range session.Sessions() {
		sid := sess.ID
		fmt.Fprintf(&sb, "%s\tsession/%s\n", sid, name)
		for _, ag := range sess.Agents() {
			fmt.Fprintf(&sb, "%s\tsession/%s/agent/%s\n", ag.ID(), name, ag.Name())
		}
	}
	return []byte(sb.String()), nil
}

var errNoBypass = fmt.Errorf("bypass broker not available")

func readBypassPolicy(b *bypass.Broker) ([]byte, error) {
	if b == nil {
		return nil, errNoBypass
	}
	p := b.GlobalPolicy().Global()
	return p.Marshal()
}

func writeBypassPolicy(b *bypass.Broker, data []byte) error {
	if b == nil {
		return errNoBypass
	}
	var p bypass.Policy
	if err := bypass.ParsePolicy(data, &p); err != nil {
		return err
	}
	return b.GlobalPolicy().SetGlobal(p)
}

func readBypassRequest(req *bypass.Request) ([]byte, error) {
	return []byte(req.Summary() + "\n"), nil
}

func writeBypassRequest(b *bypass.Broker, req *bypass.Request, data []byte) error {
	cmd := strings.TrimSpace(string(data))
	var res bypass.Resolution
	switch cmd {
	case "approve":
		res = bypass.ResolveApprove
	case "deny":
		res = bypass.ResolveDeny
	case "persist":
		res = bypass.ResolvePersist
	default:
		return fmt.Errorf("unknown resolution: %s (use approve/deny/persist)", cmd)
	}
	if !b.Resolve(req.ID, res) {
		return fmt.Errorf("request already resolved or timed out")
	}
	return nil
}