package executor

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"sync"

	"github.com/modelcontextprotocol/go-sdk/mcp"
	"github.com/thepeterstone/claudomator/internal/role"
)

// Registry maps per-task MCP bearer tokens to a built agent MCP server. A token
// is minted when a runner spawns an agent subprocess and revoked when it exits,
// so the server resolves task context from the token alone and never trusts an
// agent-supplied task ID.
type Registry struct {
	mu      sync.RWMutex
	servers map[string]*mcp.Server
}

func NewRegistry() *Registry {
	return &Registry{servers: make(map[string]*mcp.Server)}
}

// Mint creates a token bound to a freshly built MCP server for ch.
func (r *Registry) Mint(ch AgentChannel) (string, error) {
	buf := make([]byte, 32)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	token := hex.EncodeToString(buf)
	r.mu.Lock()
	r.servers[token] = newAgentServer(ch)
	r.mu.Unlock()
	return token, nil
}

func (r *Registry) server(token string) (*mcp.Server, bool) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	s, ok := r.servers[token]
	return s, ok
}

func (r *Registry) Revoke(token string) {
	r.mu.Lock()
	delete(r.servers, token)
	r.mu.Unlock()
}

type askUserInput struct {
	Question string   `json:"question" jsonschema:"the question to ask the user; phrase it as a real question ending with a question mark"`
	Options  []string `json:"options,omitempty" jsonschema:"optional list of suggested answer choices"`
}

type reportSummaryInput struct {
	Summary string `json:"summary" jsonschema:"a 2-5 sentence summary of what you did and the outcome"`
}

type spawnSubtaskInput struct {
	Name         string   `json:"name" jsonschema:"short descriptive name for the subtask"`
	Instructions string   `json:"instructions" jsonschema:"complete instructions for the subtask agent"`
	Model        string   `json:"model,omitempty" jsonschema:"optional model override, e.g. sonnet or opus"`
	MaxBudgetUSD float64  `json:"max_budget_usd,omitempty" jsonschema:"optional budget cap in USD"`
	Role         string   `json:"role,omitempty" jsonschema:"optional role name to dispatch the subtask through instead of a fixed model (e.g. an evaluator role); when set, model is ignored and the role's escalation ladder picks the provider/model"`
	DependsOn    []string `json:"depends_on,omitempty" jsonschema:"optional list of sibling subtask IDs (returned by prior spawn_subtask calls in this same decomposition) this subtask must wait for before it can run"`
}

type recordProgressInput struct {
	Message string `json:"message" jsonschema:"a short progress note describing what you are doing"`
}

type proposeEpicInput struct {
	Name        string   `json:"name" jsonschema:"short descriptive name for the epic; matched by exact name to reuse an existing epic instead of creating a duplicate"`
	Description string   `json:"description,omitempty" jsonschema:"optional longer description of the initiative"`
	StoryIDs    []string `json:"story_ids" jsonschema:"the story IDs to group under this epic"`
}

// proposeRoleConfigInput mirrors internal/role.RoleConfig's fields directly
// (same json tags) rather than defining a parallel shape, so the tool's
// input decodes straight into a role.RoleConfig with no field-by-field
// translation. See propose_role_config below.
type proposeRoleConfigInput struct {
	Role             string      `json:"role" jsonschema:"the role name this config applies to (e.g. an existing role like builder, or a new one)"`
	SystemPrompt     string      `json:"system_prompt,omitempty" jsonschema:"system prompt appended for tasks dispatched through this role"`
	Tools            []string    `json:"tools,omitempty" jsonschema:"optional tool allowlist for this role"`
	SandboxKind      string      `json:"sandbox_kind,omitempty" jsonschema:"optional sandbox kind for this role"`
	DefaultBudgetUSD float64     `json:"default_budget_usd,omitempty" jsonschema:"optional estimated budget in USD, used when the scheduler considers escalating this role's tasks"`
	EscalationLadder []role.Tier `json:"escalation_ladder,omitempty" jsonschema:"ordered list of escalation tiers; each has candidates (provider/model pairs), an optional selection_mode (round_robin|single), and max_retries"`
}

func (in proposeRoleConfigInput) toRoleConfig() role.RoleConfig {
	return role.RoleConfig{
		Role:             in.Role,
		SystemPrompt:     in.SystemPrompt,
		Tools:            in.Tools,
		SandboxKind:      in.SandboxKind,
		DefaultBudgetUSD: in.DefaultBudgetUSD,
		EscalationLadder: in.EscalationLadder,
	}
}

func textResult(text string) *mcp.CallToolResult {
	return &mcp.CallToolResult{Content: []mcp.Content{&mcp.TextContent{Text: text}}}
}

// newAgentServer builds an MCP server exposing the five agent tools bound to ch.
func newAgentServer(ch AgentChannel) *mcp.Server {
	s := mcp.NewServer(&mcp.Implementation{Name: "claudomator", Version: "1"}, nil)

	mcp.AddTool(s, &mcp.Tool{
		Name:        "ask_user",
		Description: "Ask the user a question when you genuinely need a decision to proceed. Your turn ends after calling this; the task is resumed with the user's answer. Prefer making a reasonable decision and noting it in report_summary over asking.",
	}, func(ctx context.Context, _ *mcp.CallToolRequest, in askUserInput) (*mcp.CallToolResult, any, error) {
		q := map[string]any{"text": in.Question}
		if len(in.Options) > 0 {
			q["options"] = in.Options
		}
		payload, _ := json.Marshal(q)
		ans, err := ch.AskUser(ctx, string(payload))
		if errors.Is(err, ErrAgentBlocked) {
			return textResult("Question recorded. End your turn now without calling any more tools; the task will be resumed once the user answers."), nil, nil
		}
		if err != nil {
			return nil, nil, err
		}
		return textResult(ans), nil, nil
	})

	mcp.AddTool(s, &mcp.Tool{
		Name:        "report_summary",
		Description: "Record a concise summary of what you accomplished. Call this before finishing.",
	}, func(ctx context.Context, _ *mcp.CallToolRequest, in reportSummaryInput) (*mcp.CallToolResult, any, error) {
		if err := ch.ReportSummary(ctx, in.Summary); err != nil {
			return nil, nil, err
		}
		return textResult("Summary recorded."), nil, nil
	})

	mcp.AddTool(s, &mcp.Tool{
		Name:        "spawn_subtask",
		Description: "Create a child task to be executed separately. Use this to break large work into focused pieces, then finish your turn.",
	}, func(ctx context.Context, _ *mcp.CallToolRequest, in spawnSubtaskInput) (*mcp.CallToolResult, any, error) {
		id, err := ch.SpawnSubtask(ctx, SubtaskSpec{
			Name:         in.Name,
			Instructions: in.Instructions,
			Model:        in.Model,
			MaxBudgetUSD: in.MaxBudgetUSD,
			Role:         in.Role,
			DependsOn:    in.DependsOn,
		})
		if err != nil {
			return nil, nil, err
		}
		return textResult("Created subtask " + id), nil, nil
	})

	mcp.AddTool(s, &mcp.Tool{
		Name:        "record_progress",
		Description: "Record a short progress note that appears in the task timeline.",
	}, func(ctx context.Context, _ *mcp.CallToolRequest, in recordProgressInput) (*mcp.CallToolResult, any, error) {
		if err := ch.RecordProgress(ctx, in.Message); err != nil {
			return nil, nil, err
		}
		return textResult("Noted."), nil, nil
	})

	mcp.AddTool(s, &mcp.Tool{
		Name:        "propose_epic",
		Description: "Group one or more stories under a new or existing epic (matched by exact name) when they form a cohesive initiative. Only call this when you've been given several story IDs and independently judge that they belong together.",
	}, func(ctx context.Context, _ *mcp.CallToolRequest, in proposeEpicInput) (*mcp.CallToolResult, any, error) {
		id, err := ch.ProposeEpic(ctx, EpicProposal{
			Name:        in.Name,
			Description: in.Description,
			StoryIDs:    in.StoryIDs,
		})
		if err != nil {
			return nil, nil, err
		}
		return textResult("Proposed epic " + id), nil, nil
	})

	mcp.AddTool(s, &mcp.Tool{
		Name:        "propose_role_config",
		Description: "Propose a new draft configuration version for a role, after reflecting on what happened (e.g. during a story retro). Creates a new draft role_configs row for a human to review and activate via POST /api/roles/{role}/activate -- it never changes what is currently active.",
	}, func(ctx context.Context, _ *mcp.CallToolRequest, in proposeRoleConfigInput) (*mcp.CallToolResult, any, error) {
		version, err := ch.ProposeRoleConfig(ctx, in.toRoleConfig())
		if err != nil {
			return nil, nil, err
		}
		return textResult(fmt.Sprintf("Proposed role config %s v%d (draft)", in.Role, version)), nil, nil
	})

	return s
}

func bearerToken(r *http.Request) string {
	h := r.Header.Get("Authorization")
	if h == "" {
		return ""
	}
	return strings.TrimSpace(strings.TrimPrefix(h, "Bearer "))
}

// NewAgentMCPHandler returns the HTTP handler for the per-task agent MCP server.
// It resolves the request's bearer token to the server for that task's run;
// unknown tokens yield a 400 from the underlying handler.
func NewAgentMCPHandler(reg *Registry) http.Handler {
	return mcp.NewStreamableHTTPHandler(func(r *http.Request) *mcp.Server {
		s, ok := reg.server(bearerToken(r))
		if !ok {
			return nil
		}
		return s
	}, nil)
}