package chattool

import (
	"context"
	"io"
	"path/filepath"
	"strings"

	"charm.land/fantasy"

	"github.com/coder/coder/v2/codersdk/workspacesdk"
)

const maxProposePlanSize = 32 * 1024 // 32 KiB

// ProposePlanOptions configures the propose_plan tool.
type ProposePlanOptions struct {
	GetWorkspaceConn func(context.Context) (workspacesdk.AgentConn, error)
	ResolvePlanPath  func(context.Context) (chatPath string, home string, err error)
	StoreFile        StoreFileFunc
	IsPlanTurn       bool
}

// ProposePlanArgs are the arguments for the propose_plan tool.
type ProposePlanArgs struct {
	Path string `json:"path"`
}

// ProposePlan returns a tool that presents a Markdown plan file from the
// workspace for user review.
func ProposePlan(options ProposePlanOptions) fantasy.AgentTool {
	return fantasy.NewAgentTool(
		"propose_plan",
		"Present a Markdown plan file from the workspace for user review. "+
			"The file must already exist with a .md extension. Use write_file to create it or edit_files to refine it before calling this tool. "+
			"Pass the absolute file path to the plan. Important: use the chat-specific absolute plan path, not a generic path like PLAN.md in the home directory. "+
			"The tool reads the content from the workspace.",
		func(ctx context.Context, args ProposePlanArgs, _ fantasy.ToolCall) (fantasy.ToolResponse, error) {
			if options.IsPlanTurn {
				planPath, err := resolvePlanTurnPath(ctx, options.ResolvePlanPath)
				if err != nil {
					return fantasy.NewTextErrorResponse(err.Error()), nil
				}
				path := strings.TrimSpace(args.Path)
				switch {
				case path == "":
					args.Path = planPath
				case path != planPath:
					return fantasy.NewTextErrorResponse("during plan turns, propose_plan path must be " + planPath), nil
				default:
					args.Path = path
				}
			}
			if options.GetWorkspaceConn == nil {
				return fantasy.NewTextErrorResponse("workspace connection resolver is not configured"), nil
			}
			if options.StoreFile == nil {
				return fantasy.NewTextErrorResponse("file storage is not configured"), nil
			}
			conn, err := options.GetWorkspaceConn(ctx)
			if err != nil {
				return fantasy.NewTextErrorResponse(err.Error()), nil
			}
			return executeProposePlanTool(ctx, conn, args, options.ResolvePlanPath, options.StoreFile)
		},
	)
}

func executeProposePlanTool(
	ctx context.Context,
	conn workspacesdk.AgentConn,
	args ProposePlanArgs,
	resolvePlanPath func(context.Context) (chatPath string, home string, err error),
	storeFile StoreFileFunc,
) (fantasy.ToolResponse, error) {
	requestedPath := strings.TrimSpace(args.Path)
	if requestedPath == "" {
		return fantasy.NewTextErrorResponse("path is required (use the chat-specific absolute plan path)"), nil
	}
	if !strings.HasSuffix(requestedPath, ".md") {
		return fantasy.NewTextErrorResponse("path must end with .md"), nil
	}

	hasPlanFileName := looksLikePlanFileName(requestedPath)
	if hasPlanFileName && !isAbsolutePath(requestedPath) {
		return fantasy.NewTextErrorResponse(
			"plan files must use absolute paths; use the chat-specific absolute plan path",
		), nil
	}

	if resolvePlanPath != nil && hasPlanFileName {
		chatPath, home, err := resolvePlanPath(ctx)
		if resp, rejected := rejectSharedPlanPath(requestedPath, home, chatPath, err); rejected {
			return resp, nil
		}
	}

	rc, _, err := conn.ReadFile(ctx, requestedPath, 0, maxProposePlanSize+1)
	if err != nil {
		return fantasy.NewTextErrorResponse(err.Error()), nil
	}
	defer rc.Close()

	data, err := io.ReadAll(rc)
	if err != nil {
		return fantasy.NewTextErrorResponse(err.Error()), nil
	}
	if len(data) == 0 || strings.TrimSpace(string(data)) == "" {
		return fantasy.NewTextErrorResponse("plan file is empty; write your plan to " + requestedPath + " before proposing"), nil
	}
	if int64(len(data)) > maxProposePlanSize {
		return fantasy.NewTextErrorResponse("plan file exceeds 32 KiB size limit"), nil
	}

	attachment, err := storeFile(ctx, filepath.Base(requestedPath), requestedPath, data)
	if err != nil {
		return fantasy.NewTextErrorResponse("failed to store plan file: " + err.Error()), nil
	}

	return WithAttachments(toolResponse(map[string]any{
		"ok":         true,
		"path":       requestedPath,
		"kind":       "plan",
		"file_id":    attachment.FileID.String(),
		"media_type": attachment.MediaType,
	}), attachment), nil
}