/*
Copyright 2026 LocoStack.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package reconciler

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"maps"
	"sort"
	"strings"

	"github.com/LocoStack/loco-operator/api/v1alpha1"
	"github.com/LocoStack/loco-operator/pkg/templates/litellm"
	"github.com/LocoStack/loco-operator/pkg/templates/opencode"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
)

// LocoOpenCodeAgentReconciler reconciles the "opencode" template, running the OpenCode
// CLI (https://opencode.ai) in headless server mode. Unlike loco-agents, OpenCode is
// configured entirely through its own config file rather than a LocoStack-specific
// shim, so this reconciler translates AgentComponents into OpenCode's native schema:
// a custom "openai-compatible" provider for the model, native "mcp" entries for tools,
// and native SKILL.md discovery for skills (via AddSkillsToTmpl).
//
// KnowledgeBases and Agents (subagents) dependencies are resolved by getDependencies
// like any other agent template, but intentionally left unused here: OpenCode has no
// native knowledge-base/RAG concept, and no native support for remote (A2A) subagents.
type LocoOpenCodeAgentReconciler struct {
	*DefaultComponentReconciler
	*AgentReconciler
	client    client.Client
	scheme    *runtime.Scheme
	stack     *v1alpha1.Stack
	component *v1alpha1.Component
}

func NewLocoOpenCodeAgentReconciler(client client.Client, scheme *runtime.Scheme, stack *v1alpha1.Stack, component *v1alpha1.Component) *LocoOpenCodeAgentReconciler {
	return &LocoOpenCodeAgentReconciler{
		DefaultComponentReconciler: NewDefaultComponentReconciler(client, scheme, stack, component),
		AgentReconciler:            NewAgentReconciler(client, scheme, stack, component),
		client:                     client,
		scheme:                     scheme,
		stack:                      stack,
		component:                  component,
	}
}

func (r *LocoOpenCodeAgentReconciler) ReconcileComponent(ctx context.Context, tmpl *v1alpha1.Template, variables map[string]string) ([]client.Object, error) {
	deps, comps, err := r.getDependencies(ctx)
	if err != nil {
		return nil, fmt.Errorf("Failed to get dependencies for %s: %w", r.component.Name, err)
	}

	configHash, err := r.reconcileOpenCodeConfig(ctx, r.component.Spec.Variables["systemPrompt"], comps)
	if err != nil {
		return nil, fmt.Errorf("Failed to reconcile config for %s: %w", r.component.Name, err)
	}

	skillsHash, err := r.AddSkillsToTmpl(ctx, comps, tmpl, opencode.OpenCodeSkillsRoot)
	if err != nil {
		return nil, fmt.Errorf("Failed to mount skills for %s: %w", r.component.Name, err)
	}

	if tmpl.Metadata.Annotations == nil {
		tmpl.Metadata.Annotations = make(map[string]string)
	}
	// OpenCode discovers its skills at startup and the mounted ConfigMaps change under a
	// running Pod, so the skill files count towards the Pod template just like the config
	h := sha256.Sum256([]byte(configHash + skillsHash))
	maps.Copy(tmpl.Metadata.Annotations, map[string]string{
		"locostack.com/configHash": hex.EncodeToString(h[:]),
	})

	if _, err := r.DefaultComponentReconciler.ReconcileComponent(ctx, tmpl, variables); err != nil {
		return nil, err
	}
	return deps, nil
}

type openCodeProviderModel struct {
	Name string `json:"name,omitempty"`
}

type openCodeProviderOptions struct {
	BaseURL string `json:"baseURL"`
	APIKey  string `json:"apiKey,omitempty"`
}

type openCodeProvider struct {
	NPM     string                           `json:"npm"`
	Name    string                           `json:"name,omitempty"`
	Options openCodeProviderOptions          `json:"options"`
	Models  map[string]openCodeProviderModel `json:"models"`
}

type openCodeMCPServer struct {
	Type    string            `json:"type"`
	URL     string            `json:"url"`
	Headers map[string]string `json:"headers,omitempty"`
}

type openCodeAgentConfig struct {
	Prompt string `json:"prompt,omitempty"`
}

type openCodeConfig struct {
	Schema   string                         `json:"$schema"`
	Provider map[string]openCodeProvider    `json:"provider"`
	Model    string                         `json:"model,omitempty"`
	MCP      map[string]openCodeMCPServer   `json:"mcp,omitempty"`
	Agent    map[string]openCodeAgentConfig `json:"agent,omitempty"`
}

const openCodeModelProviderID = "locostack"

func (r *LocoOpenCodeAgentReconciler) reconcileOpenCodeConfig(ctx context.Context, systemPrompt string, comps *AgentComponents) (string, error) {
	cfg := openCodeConfig{
		Schema: "https://opencode.ai/config.json",
		Provider: map[string]openCodeProvider{
			openCodeModelProviderID: {
				NPM:  "@ai-sdk/openai-compatible",
				Name: "LocoStack",
				Options: openCodeProviderOptions{
					BaseURL: comps.Model.URL,
					APIKey:  comps.GatewayKey,
				},
				Models: map[string]openCodeProviderModel{
					comps.Model.Name: {},
				},
			},
		},
		Model: fmt.Sprintf("%s/%s", openCodeModelProviderID, comps.Model.Name),
	}

	if systemPrompt != "" {
		cfg.Agent = map[string]openCodeAgentConfig{
			"build": {Prompt: systemPrompt},
		}
	}

	if len(comps.Tools) > 0 {
		cfg.MCP = make(map[string]openCodeMCPServer)
		if comps.Gateway.URL != "" {
			toolNames := make([]string, 0, len(comps.Tools))
			for _, tool := range comps.Tools {
				toolNames = append(toolNames, tool.Name)
			}
			sort.Strings(toolNames)
			cfg.MCP["litellm"] = openCodeMCPServer{
				Type: "remote",
				URL:  fmt.Sprintf("%s/%s/mcp", comps.Gateway.URL, strings.Join(toolNames, ",")),
				Headers: map[string]string{
					litellm.MCPAuthHeaderName: "Bearer " + comps.GatewayKey,
				},
			}
		} else {
			for _, tool := range comps.Tools {
				cfg.MCP[tool.Name] = openCodeMCPServer{Type: "remote", URL: tool.URL}
			}
		}
	}

	jsonBytes, err := json.Marshal(cfg)
	if err != nil {
		return "", fmt.Errorf("marshaling opencode config: %w", err)
	}
	h := sha256.Sum256(jsonBytes)
	configHash := hex.EncodeToString(h[:])
	secret := &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: r.ResourceName("config"), Namespace: r.component.GetNamespace()}}
	_, err = controllerutil.CreateOrUpdate(ctx, r.client, secret, func() error {
		if secret.Labels == nil {
			secret.Labels = map[string]string{}
		}
		maps.Copy(secret.Labels, r.ResourceLabels())
		if secret.Annotations == nil {
			secret.Annotations = make(map[string]string)
		}
		secret.Annotations["hash"] = configHash
		secret.Data = map[string][]byte{
			"opencode.json": jsonBytes,
		}
		return controllerutil.SetControllerReference(r.component, secret, r.scheme)
	})
	return configHash, err
}