package ast

import (
	"fmt"
	"iter"
	"slices"
	"strings"
	"sync"

	"github.com/elliotchance/orderedmap/v3"
	"gopkg.in/yaml.v3"

	"github.com/go-task/task/v3/errors"
	"github.com/go-task/task/v3/internal/filepathext"
	"github.com/go-task/task/v3/internal/sort"
)

type (
	// Tasks is an ordered map of task names to Tasks.
	Tasks struct {
		om    *orderedmap.OrderedMap[string, *Task]
		mutex sync.RWMutex
	}
	// A TaskElement is a key-value pair that is used for initializing a Tasks
	// structure.
	TaskElement orderedmap.Element[string, *Task]
)

// NewTasks creates a new instance of Tasks and initializes it with the provided
// set of elements, if any. The elements are added in the order they are passed.
func NewTasks(els ...*TaskElement) *Tasks {
	tasks := &Tasks{
		om: orderedmap.NewOrderedMap[string, *Task](),
	}
	for _, el := range els {
		tasks.Set(el.Key, el.Value)
	}
	return tasks
}

// Len returns the number of variables in the Tasks map.
func (tasks *Tasks) Len() int {
	if tasks == nil || tasks.om == nil {
		return 0
	}
	defer tasks.mutex.RUnlock()
	tasks.mutex.RLock()
	return tasks.om.Len()
}

// Get returns the value the the task with the provided key and a boolean that
// indicates if the value was found or not. If the value is not found, the
// returned task is a zero value and the bool is false.
func (tasks *Tasks) Get(key string) (*Task, bool) {
	if tasks == nil || tasks.om == nil {
		return &Task{}, false
	}
	defer tasks.mutex.RUnlock()
	tasks.mutex.RLock()
	return tasks.om.Get(key)
}

// Set sets the value of the task with the provided key to the provided value.
// If the task already exists, its value is updated. If the task does not exist,
// it is created.
func (tasks *Tasks) Set(key string, value *Task) bool {
	if tasks == nil {
		tasks = NewTasks()
	}
	if tasks.om == nil {
		tasks.om = orderedmap.NewOrderedMap[string, *Task]()
	}
	defer tasks.mutex.Unlock()
	tasks.mutex.Lock()
	return tasks.om.Set(key, value)
}

// All returns an iterator that loops over all task key-value pairs in the order
// specified by the sorter.
func (t *Tasks) All(sorter sort.Sorter) iter.Seq2[string, *Task] {
	if t == nil || t.om == nil {
		return func(yield func(string, *Task) bool) {}
	}
	if sorter == nil {
		return t.om.AllFromFront()
	}
	return func(yield func(string, *Task) bool) {
		for _, key := range sorter(slices.Collect(t.om.Keys()), nil) {
			el := t.om.GetElement(key)
			if !yield(el.Key, el.Value) {
				return
			}
		}
	}
}

// Keys returns an iterator that loops over all task keys in the order specified
// by the sorter.
func (t *Tasks) Keys(sorter sort.Sorter) iter.Seq[string] {
	return func(yield func(string) bool) {
		for k := range t.All(sorter) {
			if !yield(k) {
				return
			}
		}
	}
}

// Values returns an iterator that loops over all task values in the order
// specified by the sorter.
func (t *Tasks) Values(sorter sort.Sorter) iter.Seq[*Task] {
	return func(yield func(*Task) bool) {
		for _, v := range t.All(sorter) {
			if !yield(v) {
				return
			}
		}
	}
}

func (t1 *Tasks) Merge(t2 *Tasks, include *Include, includedTaskfileVars *Vars) error {
	defer t2.mutex.RUnlock()
	t2.mutex.RLock()
	for name, v := range t2.All(nil) {
		// We do a deep copy of the task struct here to ensure that no data can
		// be changed elsewhere once the taskfile is merged.
		task := v.DeepCopy()
		// Set the task to internal if EITHER the included task or the included
		// taskfile are marked as internal
		task.Internal = task.Internal || (include != nil && include.Internal)
		taskName := name

		// if the task is in the exclude list, don't add it to the merged taskfile
		if slices.Contains(include.Excludes, name) {
			continue
		}

		if !include.Flatten {
			// Add namespaces to task dependencies
			for _, dep := range task.Deps {
				if dep != nil && dep.Task != "" {
					dep.Task = taskNameWithNamespace(dep.Task, include.Namespace)
				}
			}

			// Add namespaces to task commands
			for _, cmd := range task.Cmds {
				if cmd != nil && cmd.Task != "" {
					cmd.Task = taskNameWithNamespace(cmd.Task, include.Namespace)
				}
			}

			// Add namespaces to task aliases
			for i, alias := range task.Aliases {
				task.Aliases[i] = taskNameWithNamespace(alias, include.Namespace)
			}

			// Add namespace aliases
			if include != nil {
				for _, namespaceAlias := range include.Aliases {
					task.Aliases = append(task.Aliases, taskNameWithNamespace(task.Task, namespaceAlias))
					for _, alias := range v.Aliases {
						task.Aliases = append(task.Aliases, taskNameWithNamespace(alias, namespaceAlias))
					}
				}
			}

			taskName = taskNameWithNamespace(name, include.Namespace)
			task.Namespace = include.Namespace
			task.Task = taskName
		}

		if include.AdvancedImport {
			task.Dir = filepathext.SmartJoin(include.Dir, task.Dir)
			if task.IncludeVars == nil {
				task.IncludeVars = NewVars()
			}
			task.IncludeVars.Merge(include.Vars, nil)
			task.IncludedTaskfileVars = includedTaskfileVars.DeepCopy()
		}

		if _, ok := t1.Get(taskName); ok {
			return &errors.TaskNameFlattenConflictError{
				TaskName: taskName,
				Include:  include.Namespace,
			}
		}
		// Add the task to the merged taskfile
		t1.Set(taskName, task)
	}

	// If the included Taskfile has a default task, is not flattened and the
	// parent namespace has no task with a matching name, we can add an alias so
	// that the user can run the included Taskfile's default task without
	// specifying its full name. If the parent namespace has aliases, we add
	// another alias for each of them.
	_, t2DefaultExists := t2.Get("default")
	_, t1NamespaceExists := t1.Get(include.Namespace)
	if t2DefaultExists && !t1NamespaceExists && !include.Flatten {
		defaultTaskName := fmt.Sprintf("%s:default", include.Namespace)
		t1DefaultTask, ok := t1.Get(defaultTaskName)
		if ok {
			t1DefaultTask.Aliases = append(t1DefaultTask.Aliases, include.Namespace)
			t1DefaultTask.Aliases = slices.Concat(t1DefaultTask.Aliases, include.Aliases)
		}
	}

	return nil
}

func (t *Tasks) UnmarshalYAML(node *yaml.Node) error {
	if t == nil || t.om == nil {
		*t = *NewTasks()
	}
	switch node.Kind {
	case yaml.MappingNode:
		// NOTE: orderedmap does not have an unmarshaler, so we have to decode
		// the map manually. We increment over 2 values at a time and assign
		// them as a key-value pair.
		for i := 0; i < len(node.Content); i += 2 {
			keyNode := node.Content[i]
			valueNode := node.Content[i+1]

			// Decode the value node into a Task struct
			var v Task
			if err := valueNode.Decode(&v); err != nil {
				return errors.NewTaskfileDecodeError(err, node)
			}

			// Set the task name and location
			v.Task = keyNode.Value
			v.Location = &Location{
				Line:   keyNode.Line,
				Column: keyNode.Column,
			}

			// Add the task to the ordered map
			t.Set(keyNode.Value, &v)
		}
		return nil
	}

	return errors.NewTaskfileDecodeError(nil, node).WithTypeMessage("tasks")
}

func taskNameWithNamespace(taskName string, namespace string) string {
	if strings.HasPrefix(taskName, NamespaceSeparator) {
		return strings.TrimPrefix(taskName, NamespaceSeparator)
	}
	return fmt.Sprintf("%s%s%s", namespace, NamespaceSeparator, taskName)
}