package github

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"github.com/github/github-mcp-server/pkg/translations"
	"github.com/go-viper/mapstructure/v2"
	"github.com/google/go-github/v69/github"
	"github.com/mark3labs/mcp-go/mcp"
	"github.com/mark3labs/mcp-go/server"
	"github.com/shurcooL/githubv4"
)

// GetIssue creates a tool to get details of a specific issue in a GitHub repository.
func GetIssue(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
	return mcp.NewTool("get_issue",
			mcp.WithDescription(t("TOOL_GET_ISSUE_DESCRIPTION", "Get details of a specific issue in a GitHub repository.")),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:        t("TOOL_GET_ISSUE_USER_TITLE", "Get issue details"),
				ReadOnlyHint: toBoolPtr(true),
			}),
			mcp.WithString("owner",
				mcp.Required(),
				mcp.Description("The owner of the repository"),
			),
			mcp.WithString("repo",
				mcp.Required(),
				mcp.Description("The name of the repository"),
			),
			mcp.WithNumber("issue_number",
				mcp.Required(),
				mcp.Description("The number of the issue"),
			),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			owner, err := requiredParam[string](request, "owner")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			repo, err := requiredParam[string](request, "repo")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			issueNumber, err := RequiredInt(request, "issue_number")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			client, err := getClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}
			issue, resp, err := client.Issues.Get(ctx, owner, repo, issueNumber)
			if err != nil {
				return nil, fmt.Errorf("failed to get issue: %w", err)
			}
			defer func() { _ = resp.Body.Close() }()

			if resp.StatusCode != http.StatusOK {
				body, err := io.ReadAll(resp.Body)
				if err != nil {
					return nil, fmt.Errorf("failed to read response body: %w", err)
				}
				return mcp.NewToolResultError(fmt.Sprintf("failed to get issue: %s", string(body))), nil
			}

			// Apply content filtering
			filterCfg := &ContentFilteringConfig{
				DisableContentFiltering: false, // Default to enabled
			}
			// TODO: Pass server configuration through client context once it's available
			filteredIssue := FilterIssue(issue, filterCfg)

			r, err := json.Marshal(filteredIssue)
			if err != nil {
				return nil, fmt.Errorf("failed to marshal issue: %w", err)
			}

			return mcp.NewToolResultText(string(r)), nil
		}
}

// AddIssueComment creates a tool to add a comment to an issue.
func AddIssueComment(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
	return mcp.NewTool("add_issue_comment",
			mcp.WithDescription(t("TOOL_ADD_ISSUE_COMMENT_DESCRIPTION", "Add a comment to a specific issue in a GitHub repository.")),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:        t("TOOL_ADD_ISSUE_COMMENT_USER_TITLE", "Add comment to issue"),
				ReadOnlyHint: toBoolPtr(false),
			}),
			mcp.WithString("owner",
				mcp.Required(),
				mcp.Description("Repository owner"),
			),
			mcp.WithString("repo",
				mcp.Required(),
				mcp.Description("Repository name"),
			),
			mcp.WithNumber("issue_number",
				mcp.Required(),
				mcp.Description("Issue number to comment on"),
			),
			mcp.WithString("body",
				mcp.Required(),
				mcp.Description("Comment content"),
			),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			owner, err := requiredParam[string](request, "owner")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			repo, err := requiredParam[string](request, "repo")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			issueNumber, err := RequiredInt(request, "issue_number")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			body, err := requiredParam[string](request, "body")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			comment := &github.IssueComment{
				Body: github.Ptr(body),
			}

			client, err := getClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}
			createdComment, resp, err := client.Issues.CreateComment(ctx, owner, repo, issueNumber, comment)
			if err != nil {
				return nil, fmt.Errorf("failed to create comment: %w", err)
			}
			defer func() { _ = resp.Body.Close() }()

			if resp.StatusCode != http.StatusCreated {
				body, err := io.ReadAll(resp.Body)
				if err != nil {
					return nil, fmt.Errorf("failed to read response body: %w", err)
				}
				return mcp.NewToolResultError(fmt.Sprintf("failed to create comment: %s", string(body))), nil
			}

			r, err := json.Marshal(createdComment)
			if err != nil {
				return nil, fmt.Errorf("failed to marshal response: %w", err)
			}

			return mcp.NewToolResultText(string(r)), nil
		}
}

// SearchIssues creates a tool to search for issues and pull requests.
func SearchIssues(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
	return mcp.NewTool("search_issues",
			mcp.WithDescription(t("TOOL_SEARCH_ISSUES_DESCRIPTION", "Search for issues in GitHub repositories.")),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:        t("TOOL_SEARCH_ISSUES_USER_TITLE", "Search issues"),
				ReadOnlyHint: toBoolPtr(true),
			}),
			mcp.WithString("q",
				mcp.Required(),
				mcp.Description("Search query using GitHub issues search syntax"),
			),
			mcp.WithString("sort",
				mcp.Description("Sort field by number of matches of categories, defaults to best match"),
				mcp.Enum(
					"comments",
					"reactions",
					"reactions-+1",
					"reactions--1",
					"reactions-smile",
					"reactions-thinking_face",
					"reactions-heart",
					"reactions-tada",
					"interactions",
					"created",
					"updated",
				),
			),
			mcp.WithString("order",
				mcp.Description("Sort order"),
				mcp.Enum("asc", "desc"),
			),
			WithPagination(),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			query, err := requiredParam[string](request, "q")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			sort, err := OptionalParam[string](request, "sort")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			order, err := OptionalParam[string](request, "order")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			pagination, err := OptionalPaginationParams(request)
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			opts := &github.SearchOptions{
				Sort:  sort,
				Order: order,
				ListOptions: github.ListOptions{
					PerPage: pagination.perPage,
					Page:    pagination.page,
				},
			}

			client, err := getClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}
			result, resp, err := client.Search.Issues(ctx, query, opts)
			if err != nil {
				return nil, fmt.Errorf("failed to search issues: %w", err)
			}
			defer func() { _ = resp.Body.Close() }()

			if resp.StatusCode != http.StatusOK {
				body, err := io.ReadAll(resp.Body)
				if err != nil {
					return nil, fmt.Errorf("failed to read response body: %w", err)
				}
				return mcp.NewToolResultError(fmt.Sprintf("failed to search issues: %s", string(body))), nil
			}

			// Apply content filtering
			filterCfg := &ContentFilteringConfig{
				DisableContentFiltering: false, // Default to enabled
			}
			// TODO: Pass server configuration through client context once it's available
			
			// Apply filtering to both issues and pull requests in the search results
			if result.Issues != nil {
				filteredItems := make([]*github.Issue, len(result.Issues))
				for i, issue := range result.Issues {
					filteredItems[i] = FilterIssue(issue, filterCfg)
				}
				result.Issues = filteredItems
			}

			r, err := json.Marshal(result)
			if err != nil {
				return nil, fmt.Errorf("failed to marshal response: %w", err)
			}

			return mcp.NewToolResultText(string(r)), nil
		}
}

// CreateIssue creates a tool to create a new issue in a GitHub repository.
func CreateIssue(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
	return mcp.NewTool("create_issue",
			mcp.WithDescription(t("TOOL_CREATE_ISSUE_DESCRIPTION", "Create a new issue in a GitHub repository.")),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:        t("TOOL_CREATE_ISSUE_USER_TITLE", "Open new issue"),
				ReadOnlyHint: toBoolPtr(false),
			}),
			mcp.WithString("owner",
				mcp.Required(),
				mcp.Description("Repository owner"),
			),
			mcp.WithString("repo",
				mcp.Required(),
				mcp.Description("Repository name"),
			),
			mcp.WithString("title",
				mcp.Required(),
				mcp.Description("Issue title"),
			),
			mcp.WithString("body",
				mcp.Description("Issue body content"),
			),
			mcp.WithArray("assignees",
				mcp.Description("Usernames to assign to this issue"),
				mcp.Items(
					map[string]any{
						"type": "string",
					},
				),
			),
			mcp.WithArray("labels",
				mcp.Description("Labels to apply to this issue"),
				mcp.Items(
					map[string]any{
						"type": "string",
					},
				),
			),
			mcp.WithNumber("milestone",
				mcp.Description("Milestone number"),
			),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			owner, err := requiredParam[string](request, "owner")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			repo, err := requiredParam[string](request, "repo")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			title, err := requiredParam[string](request, "title")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			// Optional parameters
			body, err := OptionalParam[string](request, "body")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			// Get assignees
			assignees, err := OptionalStringArrayParam(request, "assignees")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			// Get labels
			labels, err := OptionalStringArrayParam(request, "labels")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			// Get optional milestone
			milestone, err := OptionalIntParam(request, "milestone")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			var milestoneNum *int
			if milestone != 0 {
				milestoneNum = &milestone
			}

			// Create the issue request
			issueRequest := &github.IssueRequest{
				Title:     github.Ptr(title),
				Body:      github.Ptr(body),
				Assignees: &assignees,
				Labels:    &labels,
				Milestone: milestoneNum,
			}

			client, err := getClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}
			issue, resp, err := client.Issues.Create(ctx, owner, repo, issueRequest)
			if err != nil {
				return nil, fmt.Errorf("failed to create issue: %w", err)
			}
			defer func() { _ = resp.Body.Close() }()

			if resp.StatusCode != http.StatusCreated {
				body, err := io.ReadAll(resp.Body)
				if err != nil {
					return nil, fmt.Errorf("failed to read response body: %w", err)
				}
				return mcp.NewToolResultError(fmt.Sprintf("failed to create issue: %s", string(body))), nil
			}

			r, err := json.Marshal(issue)
			if err != nil {
				return nil, fmt.Errorf("failed to marshal response: %w", err)
			}

			return mcp.NewToolResultText(string(r)), nil
		}
}

// ListIssues creates a tool to list and filter repository issues
func ListIssues(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
	return mcp.NewTool("list_issues",
			mcp.WithDescription(t("TOOL_LIST_ISSUES_DESCRIPTION", "List issues in a GitHub repository.")),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:        t("TOOL_LIST_ISSUES_USER_TITLE", "List issues"),
				ReadOnlyHint: toBoolPtr(true),
			}),
			mcp.WithString("owner",
				mcp.Required(),
				mcp.Description("Repository owner"),
			),
			mcp.WithString("repo",
				mcp.Required(),
				mcp.Description("Repository name"),
			),
			mcp.WithString("state",
				mcp.Description("Filter by state"),
				mcp.Enum("open", "closed", "all"),
			),
			mcp.WithArray("labels",
				mcp.Description("Filter by labels"),
				mcp.Items(
					map[string]interface{}{
						"type": "string",
					},
				),
			),
			mcp.WithString("sort",
				mcp.Description("Sort order"),
				mcp.Enum("created", "updated", "comments"),
			),
			mcp.WithString("direction",
				mcp.Description("Sort direction"),
				mcp.Enum("asc", "desc"),
			),
			mcp.WithString("since",
				mcp.Description("Filter by date (ISO 8601 timestamp)"),
			),
			WithPagination(),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			owner, err := requiredParam[string](request, "owner")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			repo, err := requiredParam[string](request, "repo")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			opts := &github.IssueListByRepoOptions{}

			// Set optional parameters if provided
			opts.State, err = OptionalParam[string](request, "state")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			// Get labels
			opts.Labels, err = OptionalStringArrayParam(request, "labels")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			opts.Sort, err = OptionalParam[string](request, "sort")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			opts.Direction, err = OptionalParam[string](request, "direction")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			since, err := OptionalParam[string](request, "since")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			if since != "" {
				timestamp, err := parseISOTimestamp(since)
				if err != nil {
					return mcp.NewToolResultError(fmt.Sprintf("failed to list issues: %s", err.Error())), nil
				}
				opts.Since = timestamp
			}

			if page, ok := request.Params.Arguments["page"].(float64); ok {
				opts.Page = int(page)
			}

			if perPage, ok := request.Params.Arguments["perPage"].(float64); ok {
				opts.PerPage = int(perPage)
			}

			client, err := getClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}
			issues, resp, err := client.Issues.ListByRepo(ctx, owner, repo, opts)
			if err != nil {
				return nil, fmt.Errorf("failed to list issues: %w", err)
			}
			defer func() { _ = resp.Body.Close() }()

			if resp.StatusCode != http.StatusOK {
				body, err := io.ReadAll(resp.Body)
				if err != nil {
					return nil, fmt.Errorf("failed to read response body: %w", err)
				}
				return mcp.NewToolResultError(fmt.Sprintf("failed to list issues: %s", string(body))), nil
			}

			// Apply content filtering
			filterCfg := &ContentFilteringConfig{
				DisableContentFiltering: false, // Default to enabled
			}
			// TODO: Pass server configuration through client context once it's available
			filteredIssues := FilterIssues(issues, filterCfg)

			r, err := json.Marshal(filteredIssues)
			if err != nil {
				return nil, fmt.Errorf("failed to marshal issues: %w", err)
			}

			return mcp.NewToolResultText(string(r)), nil
		}
}

// UpdateIssue creates a tool to update an existing issue in a GitHub repository.
func UpdateIssue(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
	return mcp.NewTool("update_issue",
			mcp.WithDescription(t("TOOL_UPDATE_ISSUE_DESCRIPTION", "Update an existing issue in a GitHub repository.")),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:        t("TOOL_UPDATE_ISSUE_USER_TITLE", "Edit issue"),
				ReadOnlyHint: toBoolPtr(false),
			}),
			mcp.WithString("owner",
				mcp.Required(),
				mcp.Description("Repository owner"),
			),
			mcp.WithString("repo",
				mcp.Required(),
				mcp.Description("Repository name"),
			),
			mcp.WithNumber("issue_number",
				mcp.Required(),
				mcp.Description("Issue number to update"),
			),
			mcp.WithString("title",
				mcp.Description("New title"),
			),
			mcp.WithString("body",
				mcp.Description("New description"),
			),
			mcp.WithString("state",
				mcp.Description("New state"),
				mcp.Enum("open", "closed"),
			),
			mcp.WithArray("labels",
				mcp.Description("New labels"),
				mcp.Items(
					map[string]interface{}{
						"type": "string",
					},
				),
			),
			mcp.WithArray("assignees",
				mcp.Description("New assignees"),
				mcp.Items(
					map[string]interface{}{
						"type": "string",
					},
				),
			),
			mcp.WithNumber("milestone",
				mcp.Description("New milestone number"),
			),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			owner, err := requiredParam[string](request, "owner")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			repo, err := requiredParam[string](request, "repo")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			issueNumber, err := RequiredInt(request, "issue_number")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			// Create the issue request with only provided fields
			issueRequest := &github.IssueRequest{}

			// Set optional parameters if provided
			title, err := OptionalParam[string](request, "title")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			if title != "" {
				issueRequest.Title = github.Ptr(title)
			}

			body, err := OptionalParam[string](request, "body")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			if body != "" {
				issueRequest.Body = github.Ptr(body)
			}

			state, err := OptionalParam[string](request, "state")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			if state != "" {
				issueRequest.State = github.Ptr(state)
			}

			// Get labels
			labels, err := OptionalStringArrayParam(request, "labels")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			if len(labels) > 0 {
				issueRequest.Labels = &labels
			}

			// Get assignees
			assignees, err := OptionalStringArrayParam(request, "assignees")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			if len(assignees) > 0 {
				issueRequest.Assignees = &assignees
			}

			milestone, err := OptionalIntParam(request, "milestone")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			if milestone != 0 {
				milestoneNum := milestone
				issueRequest.Milestone = &milestoneNum
			}

			client, err := getClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}
			updatedIssue, resp, err := client.Issues.Edit(ctx, owner, repo, issueNumber, issueRequest)
			if err != nil {
				return nil, fmt.Errorf("failed to update issue: %w", err)
			}
			defer func() { _ = resp.Body.Close() }()

			if resp.StatusCode != http.StatusOK {
				body, err := io.ReadAll(resp.Body)
				if err != nil {
					return nil, fmt.Errorf("failed to read response body: %w", err)
				}
				return mcp.NewToolResultError(fmt.Sprintf("failed to update issue: %s", string(body))), nil
			}

			r, err := json.Marshal(updatedIssue)
			if err != nil {
				return nil, fmt.Errorf("failed to marshal response: %w", err)
			}

			return mcp.NewToolResultText(string(r)), nil
		}
}

// GetIssueComments creates a tool to get comments for a GitHub issue.
func GetIssueComments(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
	return mcp.NewTool("get_issue_comments",
			mcp.WithDescription(t("TOOL_GET_ISSUE_COMMENTS_DESCRIPTION", "Get comments for a specific issue in a GitHub repository.")),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:        t("TOOL_GET_ISSUE_COMMENTS_USER_TITLE", "Get issue comments"),
				ReadOnlyHint: toBoolPtr(true),
			}),
			mcp.WithString("owner",
				mcp.Required(),
				mcp.Description("Repository owner"),
			),
			mcp.WithString("repo",
				mcp.Required(),
				mcp.Description("Repository name"),
			),
			mcp.WithNumber("issue_number",
				mcp.Required(),
				mcp.Description("Issue number"),
			),
			mcp.WithNumber("page",
				mcp.Description("Page number"),
			),
			mcp.WithNumber("per_page",
				mcp.Description("Number of records per page"),
			),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			owner, err := requiredParam[string](request, "owner")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			repo, err := requiredParam[string](request, "repo")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			issueNumber, err := RequiredInt(request, "issue_number")
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			page, err := OptionalIntParamWithDefault(request, "page", 1)
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}
			perPage, err := OptionalIntParamWithDefault(request, "per_page", 30)
			if err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			opts := &github.IssueListCommentsOptions{
				ListOptions: github.ListOptions{
					Page:    page,
					PerPage: perPage,
				},
			}

			client, err := getClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}
			comments, resp, err := client.Issues.ListComments(ctx, owner, repo, issueNumber, opts)
			if err != nil {
				return nil, fmt.Errorf("failed to get issue comments: %w", err)
			}
			defer func() { _ = resp.Body.Close() }()

			if resp.StatusCode != http.StatusOK {
				body, err := io.ReadAll(resp.Body)
				if err != nil {
					return nil, fmt.Errorf("failed to read response body: %w", err)
				}
				return mcp.NewToolResultError(fmt.Sprintf("failed to get issue comments: %s", string(body))), nil
			}

			// Apply content filtering
			filterCfg := &ContentFilteringConfig{
				DisableContentFiltering: false, // Default to enabled
			}
			// TODO: Pass server configuration through client context once it's available
			filteredComments := FilterIssueComments(comments, filterCfg)

			r, err := json.Marshal(filteredComments)
			if err != nil {
				return nil, fmt.Errorf("failed to marshal response: %w", err)
			}

			return mcp.NewToolResultText(string(r)), nil
		}
}

// mvpDescription is an MVP idea for generating tool descriptions from structured data in a shared format.
// It is not intended for widespread usage and is not a complete implementation.
type mvpDescription struct {
	summary        string
	outcomes       []string
	referenceLinks []string
}

func (d *mvpDescription) String() string {
	var sb strings.Builder
	sb.WriteString(d.summary)
	if len(d.outcomes) > 0 {
		sb.WriteString("\n\n")
		sb.WriteString("This tool can help with the following outcomes:\n")
		for _, outcome := range d.outcomes {
			sb.WriteString(fmt.Sprintf("- %s\n", outcome))
		}
	}

	if len(d.referenceLinks) > 0 {
		sb.WriteString("\n\n")
		sb.WriteString("More information can be found at:\n")
		for _, link := range d.referenceLinks {
			sb.WriteString(fmt.Sprintf("- %s\n", link))
		}
	}

	return sb.String()
}

func AssignCopilotToIssue(getGQLClient GetGQLClientFn, t translations.TranslationHelperFunc) (mcp.Tool, server.ToolHandlerFunc) {
	description := mvpDescription{
		summary: "Assign Copilot to a specific issue in a GitHub repository.",
		outcomes: []string{
			"a Pull Request created with source code changes to resolve the issue",
		},
		referenceLinks: []string{
			"https://docs.github.com/en/copilot/using-github-copilot/using-copilot-coding-agent-to-work-on-tasks/about-assigning-tasks-to-copilot",
		},
	}

	return mcp.NewTool("assign_copilot_to_issue",
			mcp.WithDescription(t("TOOL_ASSIGN_COPILOT_TO_ISSUE_DESCRIPTION", description.String())),
			mcp.WithToolAnnotation(mcp.ToolAnnotation{
				Title:          t("TOOL_ASSIGN_COPILOT_TO_ISSUE_USER_TITLE", "Assign Copilot to issue"),
				ReadOnlyHint:   toBoolPtr(false),
				IdempotentHint: toBoolPtr(true),
			}),
			mcp.WithString("owner",
				mcp.Required(),
				mcp.Description("Repository owner"),
			),
			mcp.WithString("repo",
				mcp.Required(),
				mcp.Description("Repository name"),
			),
			mcp.WithNumber("issueNumber",
				mcp.Required(),
				mcp.Description("Issue number"),
			),
		),
		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
			var params struct {
				Owner       string
				Repo        string
				IssueNumber int32
			}
			if err := mapstructure.Decode(request.Params.Arguments, &params); err != nil {
				return mcp.NewToolResultError(err.Error()), nil
			}

			client, err := getGQLClient(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
			}

			// Firstly, we try to find the copilot bot in the suggested actors for the repository.
			// Although as I write this, we would expect copilot to be at the top of the list, in future, maybe
			// it will not be on the first page of responses, thus we will keep paginating until we find it.
			type botAssignee struct {
				ID       githubv4.ID
				Login    string
				TypeName string `graphql:"__typename"`
			}

			type suggestedActorsQuery struct {
				Repository struct {
					SuggestedActors struct {
						Nodes []struct {
							Bot botAssignee `graphql:"... on Bot"`
						}
						PageInfo struct {
							HasNextPage bool
							EndCursor   string
						}
					} `graphql:"suggestedActors(first: 100, after: $endCursor, capabilities: CAN_BE_ASSIGNED)"`
				} `graphql:"repository(owner: $owner, name: $name)"`
			}

			variables := map[string]any{
				"owner":     githubv4.String(params.Owner),
				"name":      githubv4.String(params.Repo),
				"endCursor": (*githubv4.String)(nil),
			}

			var copilotAssignee *botAssignee
			for {
				var query suggestedActorsQuery
				err := client.Query(ctx, &query, variables)
				if err != nil {
					return nil, err
				}

				// Iterate all the returned nodes looking for the copilot bot, which is supposed to have the
				// same name on each host. We need this in order to get the ID for later assignment.
				for _, node := range query.Repository.SuggestedActors.Nodes {
					if node.Bot.Login == "copilot-swe-agent" {
						copilotAssignee = &node.Bot
						break
					}
				}

				if !query.Repository.SuggestedActors.PageInfo.HasNextPage {
					break
				}
				variables["endCursor"] = githubv4.String(query.Repository.SuggestedActors.PageInfo.EndCursor)
			}

			// If we didn't find the copilot bot, we can't proceed any further.
			if copilotAssignee == nil {
				// The e2e tests depend upon this specific message to skip the test.
				return mcp.NewToolResultError("copilot isn't available as an assignee for this issue. Please inform the user to visit https://docs.github.com/en/copilot/using-github-copilot/using-copilot-coding-agent-to-work-on-tasks/about-assigning-tasks-to-copilot for more information."), nil
			}

			// Next let's get the GQL Node ID and current assignees for this issue because the only way to
			// assign copilot is to use replaceActorsForAssignable which requires the full list.
			var getIssueQuery struct {
				Repository struct {
					Issue struct {
						ID        githubv4.ID
						Assignees struct {
							Nodes []struct {
								ID githubv4.ID
							}
						} `graphql:"assignees(first: 100)"`
					} `graphql:"issue(number: $number)"`
				} `graphql:"repository(owner: $owner, name: $name)"`
			}

			variables = map[string]any{
				"owner":  githubv4.String(params.Owner),
				"name":   githubv4.String(params.Repo),
				"number": githubv4.Int(params.IssueNumber),
			}

			if err := client.Query(ctx, &getIssueQuery, variables); err != nil {
				return mcp.NewToolResultError(fmt.Sprintf("failed to get issue ID: %v", err)), nil
			}

			// Finally, do the assignment. Just for reference, assigning copilot to an issue that it is already
			// assigned to seems to have no impact (which is a good thing).
			var assignCopilotMutation struct {
				ReplaceActorsForAssignable struct {
					Typename string `graphql:"__typename"` // Not required but we need a selector or GQL errors
				} `graphql:"replaceActorsForAssignable(input: $input)"`
			}

			actorIDs := make([]githubv4.ID, len(getIssueQuery.Repository.Issue.Assignees.Nodes)+1)
			for i, node := range getIssueQuery.Repository.Issue.Assignees.Nodes {
				actorIDs[i] = node.ID
			}
			actorIDs[len(getIssueQuery.Repository.Issue.Assignees.Nodes)] = copilotAssignee.ID

			if err := client.Mutate(
				ctx,
				&assignCopilotMutation,
				ReplaceActorsForAssignableInput{
					AssignableID: getIssueQuery.Repository.Issue.ID,
					ActorIDs:     actorIDs,
				},
				nil,
			); err != nil {
				return nil, fmt.Errorf("failed to replace actors for assignable: %w", err)
			}

			return mcp.NewToolResultText("successfully assigned copilot to issue"), nil
		}
}

type ReplaceActorsForAssignableInput struct {
	AssignableID githubv4.ID   `json:"assignableId"`
	ActorIDs     []githubv4.ID `json:"actorIds"`
}

// parseISOTimestamp parses an ISO 8601 timestamp string into a time.Time object.
// Returns the parsed time or an error if parsing fails.
// Example formats supported: "2023-01-15T14:30:00Z", "2023-01-15"
func parseISOTimestamp(timestamp string) (time.Time, error) {
	if timestamp == "" {
		return time.Time{}, fmt.Errorf("empty timestamp")
	}

	// Try RFC3339 format (standard ISO 8601 with time)
	t, err := time.Parse(time.RFC3339, timestamp)
	if err == nil {
		return t, nil
	}

	// Try simple date format (YYYY-MM-DD)
	t, err = time.Parse("2006-01-02", timestamp)
	if err == nil {
		return t, nil
	}

	// Return error with supported formats
	return time.Time{}, fmt.Errorf("invalid ISO 8601 timestamp: %s (supported formats: YYYY-MM-DDThh:mm:ssZ or YYYY-MM-DD)", timestamp)
}