package agents

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"path/filepath"
	"time"

	"g.fc.run/misc/byre/internal/api"
	"g.fc.run/misc/byre/internal/git"
	"g.fc.run/misc/byre/internal/store"
	"g.fc.run/misc/byre/internal/todo"
)

func (m *Manager) CreateTask(ctx context.Context, project api.Project, title, createdBy, base, actor string) (api.Task, error) {
	return m.createTask(ctx, project, api.Task{Title: title, CreatedBy: createdBy}, nil, base, actor)
}

func (m *Manager) StartTask(ctx context.Context, project api.Project, creator api.User, title, prompt, model string) (api.Task, error) {
	if creator.GitName == "" || creator.GitEmail == "" {
		return api.Task{}, ErrNoGitIdentity
	}
	task, err := m.CreateTask(ctx, project, title, creator.Login, project.DefaultBranch, creator.Login)
	if err != nil {
		return api.Task{}, err
	}
	_, err = m.create(ctx, task, creator, prompt, model, creator.Login, nil)
	if err != nil {
		return api.Task{}, fmt.Errorf("task %s created, but its agent did not start: %w", task.Id, err)
	}
	return task, nil
}

func (m *Manager) StartTodo(ctx context.Context, project api.Project, creator api.User, title, model, actor, workflowName string, discuss bool) ([]api.Task, error) {
	if creator.GitName == "" || creator.GitEmail == "" {
		return nil, ErrNoGitIdentity
	}
	src, found, err := git.ReadFile(project.RepoPath, project.DefaultBranch, todo.File)
	if err != nil {
		return nil, err
	}
	if !found {
		return nil, fmt.Errorf("%w: %s has no %s", store.ErrNotFound, project.DefaultBranch, todo.File)
	}
	item, found := todo.Find(todo.Parse(src), title)
	if !found {
		return nil, fmt.Errorf("%w: %s on %s has no item %q", store.ErrNotFound, todo.File, project.DefaultBranch, title)
	}

	tasks, err := m.store.ListTasks(ctx, project.Id)
	if err != nil {
		return nil, err
	}
	for _, t := range tasks {
		if t.Status == api.TaskStatusActive && t.TodoItem != nil && *t.TodoItem == title {
			return nil, fmt.Errorf("%w: task %s is already working on %q", ErrConflict, t.Id, title)
		}
	}

	started := []api.Task{}
	if workflowName != "" {
		started, err = m.StartWorkflow(ctx, project, creator, item.Title, project.DefaultBranch, actor, workflowName, todoPrompt(item, discuss), &item.Title)
		if err != nil {
			return nil, err
		}
	} else {
		task, err := m.createTask(ctx, project, api.Task{Title: item.Title, CreatedBy: creator.Login, TodoItem: &item.Title}, nil, project.DefaultBranch, actor)
		if err != nil {
			return nil, err
		}
		_, err = m.create(ctx, task, creator, todoPrompt(item, discuss), model, actor, nil)
		if err != nil {
			return nil, fmt.Errorf("task %s created, but its agent did not start: %w", task.Id, err)
		}
		started = append(started, task)
	}
	if actor == creator.Login {
		m.setStartedTodo(creator.Login, true)
	}
	return started, nil
}

func todoPrompt(item api.TodoItem, discuss bool) string {
	p := fmt.Sprintf("Work on this item from %[1]s at the repo root:\n\n%[2]s\n\nWhen the work is done, remove this item from %[1]s in this worktree, so the removal lands in the same merge as the work.",
		todo.File, todo.Markdown(item))
	if !discuss {
		return p
	}
	return p + "\n\nThe human wants to discuss this item with you before any of it is built: a conversation, not a questionnaire. Read what you need to understand it, then end your turn with your thoughts on it in your final message: how you read it, how you would approach it, and what trade-offs or doubts you see. Don't use ask_human for this; the human replies in the chat. Keep the conversation going turn by turn, and change nothing until they tell you to build it."
}

func (m *Manager) createTask(ctx context.Context, project api.Project, t api.Task, frozen *store.FrozenWorkflow, base, actor string) (api.Task, error) {
	t.Id = store.NewID()
	t.ProjectId = project.Id
	if t.MergeTitle == "" {
		t.MergeTitle = t.Title
	}
	t.Branch = "byre/" + t.Id
	t.WorktreePath = filepath.Join(m.worktreeRoot, project.Id, t.Id)
	t.Status = api.TaskStatusActive
	t.CreatedAt = time.Now().UTC()

	var err error
	t.BaseRef, err = git.AddWorktree(project.RepoPath, t.WorktreePath, t.Branch, base)
	if err != nil {
		return api.Task{}, err
	}

	err = m.store.CreateTask(ctx, t, frozen, actor)
	if err != nil {
		rerr := git.RemoveWorktree(project.RepoPath, t.WorktreePath, t.Branch)
		if rerr != nil {
			slog.Error("remove worktree of task not created", "task", t.Id, "err", rerr)
		}
		if errors.Is(err, store.ErrParentNotOpen) {
			return api.Task{}, fmt.Errorf("%w: %w", ErrConflict, err)
		}
		return api.Task{}, err
	}
	return m.store.GetTask(ctx, t.Id)
}