package provider

import (
	"context"
	"errors"
	"fmt"

	"github.com/hashicorp/terraform-plugin-framework/path"
	"github.com/hashicorp/terraform-plugin-framework/resource"
	"github.com/hashicorp/terraform-plugin-framework/resource/schema"
	"github.com/hashicorp/terraform-plugin-framework/resource/schema/planmodifier"
	"github.com/hashicorp/terraform-plugin-framework/resource/schema/stringplanmodifier"
	"github.com/hashicorp/terraform-plugin-framework/types"
)

var _ resource.Resource = &AgentResource{}
var _ resource.ResourceWithImportState = &AgentResource{}

// AgentResource defines the resource implementation.
type AgentResource struct {
	client *Client
}

// AgentResourceModel describes the resource data model.
type AgentResourceModel struct {
	ID         types.String `tfsdk:"id"`
	Name       types.String `tfsdk:"name"`
	Token      types.String `tfsdk:"token"`
	InsertedAt types.String `tfsdk:"inserted_at"`
}

// NewAgentResource creates a new agent resource.
func NewAgentResource() resource.Resource {
	return &AgentResource{}
}

func (r *AgentResource) Metadata(ctx context.Context, req resource.MetadataRequest, resp *resource.MetadataResponse) {
	resp.TypeName = req.ProviderTypeName + "_agent"
}

func (r *AgentResource) Schema(ctx context.Context, req resource.SchemaRequest, resp *resource.SchemaResponse) {
	resp.Schema = schema.Schema{
		Description: "Manages a TowerOps agent token. Agents are deployed on customer networks to poll devices via SNMP, ping, and SSH.",
		Attributes: map[string]schema.Attribute{
			"id": schema.StringAttribute{
				Description: "The unique identifier of the agent.",
				Computed:    true,
				PlanModifiers: []planmodifier.String{
					stringplanmodifier.UseStateForUnknown(),
				},
			},
			"name": schema.StringAttribute{
				Description: "The name of the agent. Changing this forces a new resource to be created.",
				Required:    true,
				PlanModifiers: []planmodifier.String{
					stringplanmodifier.RequiresReplace(),
				},
			},
			"token": schema.StringAttribute{
				Description: "The bearer token for this agent. Only available after creation and cannot be retrieved again.",
				Computed:    true,
				Sensitive:   true,
				PlanModifiers: []planmodifier.String{
					stringplanmodifier.UseStateForUnknown(),
				},
			},
			"inserted_at": schema.StringAttribute{
				Description: "The timestamp when the agent was created.",
				Computed:    true,
				PlanModifiers: []planmodifier.String{
					stringplanmodifier.UseStateForUnknown(),
				},
			},
		},
	}
}

func (r *AgentResource) Configure(ctx context.Context, req resource.ConfigureRequest, resp *resource.ConfigureResponse) {
	if req.ProviderData == nil {
		return
	}

	client, ok := req.ProviderData.(*Client)
	if !ok {
		resp.Diagnostics.AddError(
			"Unexpected Resource Configure Type",
			fmt.Sprintf("Expected *Client, got: %T", req.ProviderData),
		)
		return
	}

	r.client = client
}

func (r *AgentResource) Create(ctx context.Context, req resource.CreateRequest, resp *resource.CreateResponse) {
	var data AgentResourceModel

	resp.Diagnostics.Append(req.Plan.Get(ctx, &data)...)
	if resp.Diagnostics.HasError() {
		return
	}

	agent := Agent{
		Name: data.Name.ValueString(),
	}

	created, err := r.client.CreateAgent(agent)
	if err != nil {
		resp.Diagnostics.AddError("Failed to create agent", err.Error())
		return
	}

	data.ID = types.StringValue(created.ID)
	data.Token = types.StringValue(created.Token)
	data.InsertedAt = types.StringValue(created.InsertedAt)

	resp.Diagnostics.Append(resp.State.Set(ctx, &data)...)
}

func (r *AgentResource) Read(ctx context.Context, req resource.ReadRequest, resp *resource.ReadResponse) {
	var data AgentResourceModel

	resp.Diagnostics.Append(req.State.Get(ctx, &data)...)
	if resp.Diagnostics.HasError() {
		return
	}

	agent, err := r.client.GetAgent(data.ID.ValueString())
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			resp.State.RemoveResource(ctx)
			return
		}
		resp.Diagnostics.AddError("Failed to read agent", err.Error())
		return
	}

	data.Name = types.StringValue(agent.Name)
	data.InsertedAt = types.StringValue(agent.InsertedAt)
	// Token is not returned by GET, preserve existing state value

	resp.Diagnostics.Append(resp.State.Set(ctx, &data)...)
}

func (r *AgentResource) Update(ctx context.Context, req resource.UpdateRequest, resp *resource.UpdateResponse) {
	// Agents only support name changes via the API, but the REST API doesn't have
	// an update endpoint. For now, if name changes, we must destroy and recreate.
	// This is handled by Terraform's ForceNew-like behavior since all mutable
	// attributes are required.
	resp.Diagnostics.AddError(
		"Agent Update Not Supported",
		"Agent tokens cannot be updated. Delete and recreate the agent to change its name.",
	)
}

func (r *AgentResource) Delete(ctx context.Context, req resource.DeleteRequest, resp *resource.DeleteResponse) {
	var data AgentResourceModel

	resp.Diagnostics.Append(req.State.Get(ctx, &data)...)
	if resp.Diagnostics.HasError() {
		return
	}

	err := r.client.DeleteAgent(data.ID.ValueString())
	if err != nil {
		resp.Diagnostics.AddError("Failed to delete agent", err.Error())
		return
	}
}

func (r *AgentResource) ImportState(ctx context.Context, req resource.ImportStateRequest, resp *resource.ImportStateResponse) {
	resource.ImportStatePassthroughID(ctx, path.Root("id"), req, resp)
}