package main

// What the module writes into the agent's machine-wide managed directory (novox/hq design 36 §1–§4).
// Pure: composed from the facts the mesh rendered, the settings the operator set and the licence the node
// holds, so what lands under /etc is tested without a machine.
//
// Three files, owned whole by this module:
//
//	managed-mcp.json        the tool servers every session loads: the mesh's console as `mesh`, and the
//	                        servers the operator declared or registered through this module. Exclusive by
//	                        the vendor's rule — a server not listed here does not load (operator's choice,
//	                        2026-10-03).
//	managed-settings.json   the keys the operator set in this module's `managed_settings` (the agent's
//	                        permissions and auto mode, say), under the mesh's own keys, which always win:
//	                        the repositories' attribution convention, the claude.ai connectors kept beside
//	                        the managed servers, and — for an API-key licence only — the key-helper. A
//	                        person's preferences are theirs, in their own settings.
//	CLAUDE.md               how a session on this mesh works, who this node is, the conventions.

import (
	"bytes"
	"encoding/json"
	"fmt"
	"regexp"
	"strings"
)

// ManagedDir is the agent's machine-wide managed directory.
const ManagedDir = "/etc/claude-code"

const meshEntry = "mesh"

// Facts are what the mesh rendered for this node.
type Facts struct {
	Node    string `json:"node"`
	Console string `json:"console"`
}

// Settings are the operator's, for the mesh or this node.
type Settings struct {
	Role       string                    `json:"role"`
	MCPServers map[string]map[string]any `json:"mcp_servers"`
	// ManagedSettings are keys of the agent's managed settings the operator sets, for the mesh or a node.
	ManagedSettings map[string]any `json:"managed_settings"`
}

// Binding is the licence this node holds, as it was last applied.
type Binding struct {
	Licence    string `json:"licence"`
	Kind       string `json:"kind"` // subscription | api-key
	Generation int64  `json:"generation,omitempty"`
}

// Servers are tool server entries by name, in the vendor's `.mcp.json` shape.
type Servers map[string]map[string]any

var serverName = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)

// EntryProblem says why the vendor's managed file would not take an entry, or "" when it would: a name of
// letters, digits, `-` and `_`, and an http/sse server with a url or a stdio server with a command.
func EntryProblem(name string, entry map[string]any) string {
	if !serverName.MatchString(name) {
		return fmt.Sprintf("%q is not a name the agent takes: letters, digits, - and _", name)
	}
	if name == meshEntry {
		return fmt.Sprintf("%q is the mesh's own entry", meshEntry)
	}
	kind, _ := entry["type"].(string)
	if kind == "" {
		kind = "stdio"
	}
	switch kind {
	case "http", "sse", "streamable-http":
		if u, _ := entry["url"].(string); u != "" {
			return ""
		}
		return fmt.Sprintf("an %s server needs a url", kind)
	case "stdio":
		if c, _ := entry["command"].(string); c != "" {
			return ""
		}
		return "a stdio server needs a command"
	}
	return fmt.Sprintf("%q is not a server type the agent knows (http, sse, stdio)", kind)
}

// jsonFile is a value as the managed files are written: two-space indent, a trailing newline, nothing
// escaped that need not be.
func jsonFile(v any) string {
	var b bytes.Buffer
	enc := json.NewEncoder(&b)
	enc.SetEscapeHTML(false)
	enc.SetIndent("", "  ")
	_ = enc.Encode(v)
	return b.String()
}

// Render composes the three files. registered — what was registered through this module and applies
// here — is laid over the servers the operator set in its settings; config is the rest of what was
// registered (ADR 0216): its settings laid over the operator's `managed_settings`, its instruction sections
// after the mesh's own text. The plugin itself is Marketplace's, and the home's PlaceHome's.
func Render(facts Facts, settings Settings, binding *Binding, helperPath string, registered Servers, config Config) map[string]string {
	return RenderWithMesh(facts, settings, binding, helperPath, registered, config, nil)
}

// RenderWithMesh is Render with what the mesh said about its tools (novox/hq ADR 0245): the "instead of"
// table, after the mesh's own text and before the sections registered for the agent.
func RenderWithMesh(facts Facts, settings Settings, binding *Binding, helperPath string, registered Servers, config Config,
	mesh *MeshTools) map[string]string {
	servers := map[string]any{}
	for _, layer := range []map[string]map[string]any{settings.MCPServers, registered} {
		for name, entry := range layer {
			if EntryProblem(name, entry) != "" {
				continue // the mesh's own entry, or one the agent would refuse
			}
			servers[name] = entry
		}
	}
	servers[meshEntry] = map[string]any{"type": "http", "url": facts.Console}

	// The operator's `managed_settings` (ADR 0213), then what was registered for the mesh, then for this node.
	managed := mergeSettings(map[string]any{}, settings.ManagedSettings)
	managed = mergeSettings(managed, RegisteredSettings(config))
	// The mesh's own keys are laid last: a setting never replaces them.
	managed["attribution"] = map[string]any{"commit": "", "pr": ""}
	managed["allowAllClaudeAiMcps"] = true
	delete(managed, "apiKeyHelper")
	// The plugin's marketplace and the plugin itself, as entries in the operator's own maps, the mesh's
	// entry winning: the operator may know more marketplaces and enable more plugins.
	for key, value := range MarketplaceKeys() {
		entries := map[string]any{}
		if held, ok := managed[key].(map[string]any); ok {
			for k, v := range held {
				entries[k] = v
			}
		}
		for k, v := range value.(map[string]any) {
			entries[k] = v
		}
		managed[key] = entries
	}
	if binding != nil && binding.Kind == "api-key" {
		managed["apiKeyHelper"] = helperPath
	}
	role := strings.TrimSpace(settings.Role)
	if role == "" {
		role = "not stated — set it in this module's settings for the node"
	}
	return map[string]string{
		"managed-mcp.json":      jsonFile(map[string]any{"mcpServers": servers}),
		"managed-settings.json": jsonFile(managed),
		"CLAUDE.md":             instructionsText(facts.Node, role) + InsteadOf(mesh) + InstructionSections(config),
	}
}