package core

import (
	"fmt"
	"strings"

	"gopkg.in/yaml.v3"
)

// rawDagStep is the loosely-typed intermediate representation of a DAG step.
type rawDagStep struct {
	Name        string            `yaml:"name"`
	ID          string            `yaml:"id"`
	Description string            `yaml:"description"`
	Command     string            `yaml:"command"`
	Script      string            `yaml:"script"`
	Args        []string          `yaml:"args"`
	Shell       string            `yaml:"shell"`
	Dir         string            `yaml:"dir"`
	WorkingDir  string            `yaml:"working_dir"`
	Depends     []string          `yaml:"depends"`
	Env         interface{}       `yaml:"env"`
	ContinueOn  rawDagContinueOn  `yaml:"continue_on"`
	RetryPolicy rawDagRetryPolicy `yaml:"retry_policy"`
	TimeoutSec  int               `yaml:"timeout_sec"`
	Output      string            `yaml:"output"`
	Tags        []string          `yaml:"tags"`
}

type rawDagContinueOn struct {
	Failure bool `yaml:"failure"`
	Skipped bool `yaml:"skipped"`
}

type rawDagRetryPolicy struct {
	Limit       int `yaml:"limit"`
	IntervalSec int `yaml:"interval_sec"`
}

// rawDagHandlers handles both handler_on and handlers aliases.
type rawDagHandlers struct {
	Init    interface{} `yaml:"init"`
	Success interface{} `yaml:"success"`
	Failure interface{} `yaml:"failure"`
	Exit    interface{} `yaml:"exit"`
}

// rawDag is the loosely-typed intermediate representation of a DAG YAML.
type rawDag struct {
	Name        string          `yaml:"name"`
	Description string          `yaml:"description"`
	Group       string          `yaml:"group"`
	Type        string          `yaml:"type"`
	WorkingDir  string          `yaml:"working_dir"`
	Shell       string          `yaml:"shell"`
	Env         interface{}     `yaml:"env"`
	Schedule    interface{}     `yaml:"schedule"`
	Steps       []rawDagStep    `yaml:"steps"`
	HandlerOn   *rawDagHandlers `yaml:"handler_on"`
	Handlers    *rawDagHandlers `yaml:"handlers"`
	Tags        []string        `yaml:"tags"`
	TimeoutSec  int             `yaml:"timeout_sec"`
}

// DagParse parses a YAML DAG definition compatible with Dagu format.
// Handles schedule as string or list, env as list of single-key maps,
// handler_on and handlers as aliases, and steps with command/script/depends.
func DagParse(data []byte) (DagDefinition, error) {
	var raw rawDag
	if err := yaml.Unmarshal(data, &raw); err != nil {
		return DagDefinition{}, fmt.Errorf("dag_parse: yaml unmarshal: %w", err)
	}

	def := DagDefinition{
		Name:       raw.Name,
		Description: raw.Description,
		Group:      raw.Group,
		Type:       raw.Type,
		WorkingDir: raw.WorkingDir,
		Shell:      raw.Shell,
		Tags:       raw.Tags,
		TimeoutSec: raw.TimeoutSec,
	}

	// Normalize env (list of single-key maps or plain map).
	dagEnv, err := normalizeEnv(raw.Env)
	if err != nil {
		return DagDefinition{}, fmt.Errorf("dag_parse: env: %w", err)
	}
	def.Env = dagEnv

	// Normalize schedule (string or list).
	def.Schedule = normalizeSchedule(raw.Schedule)

	// Normalize steps.
	steps := make([]DagStep, 0, len(raw.Steps))
	for i, rs := range raw.Steps {
		step, err := normalizeStep(rs)
		if err != nil {
			return DagDefinition{}, fmt.Errorf("dag_parse: step[%d]: %w", i, err)
		}
		steps = append(steps, step)
	}
	def.Steps = steps

	// Normalize handlers: handler_on takes precedence, fallback to handlers.
	rawHandlers := raw.HandlerOn
	if rawHandlers == nil {
		rawHandlers = raw.Handlers
	}
	if rawHandlers != nil {
		handlers, err := normalizeHandlers(rawHandlers)
		if err != nil {
			return DagDefinition{}, fmt.Errorf("dag_parse: handlers: %w", err)
		}
		def.HandlerOn = handlers
	}

	return def, nil
}

// normalizeSchedule converts schedule from string or []interface{} to []string.
func normalizeSchedule(v interface{}) []string {
	if v == nil {
		return nil
	}
	switch t := v.(type) {
	case string:
		s := strings.TrimSpace(t)
		if s == "" {
			return nil
		}
		return []string{s}
	case []interface{}:
		result := make([]string, 0, len(t))
		for _, item := range t {
			if s, ok := item.(string); ok {
				s = strings.TrimSpace(s)
				if s != "" {
					result = append(result, s)
				}
			}
		}
		return result
	}
	return nil
}

// normalizeEnv converts env from Dagu format (list of single-key maps) or plain map to map[string]string.
func normalizeEnv(v interface{}) (map[string]string, error) {
	if v == nil {
		return nil, nil
	}
	switch t := v.(type) {
	case map[string]interface{}:
		// Plain YAML map.
		result := make(map[string]string, len(t))
		for k, val := range t {
			result[k] = fmt.Sprintf("%v", val)
		}
		return result, nil
	case []interface{}:
		// Dagu format: list of single-key maps [KEY: value, KEY2: value2].
		result := make(map[string]string)
		for _, item := range t {
			m, ok := item.(map[string]interface{})
			if !ok {
				continue
			}
			for k, val := range m {
				result[k] = fmt.Sprintf("%v", val)
			}
		}
		return result, nil
	}
	return nil, fmt.Errorf("unexpected env type %T", v)
}

// normalizeStep converts a rawDagStep to a DagStep.
func normalizeStep(rs rawDagStep) (DagStep, error) {
	stepEnv, err := normalizeEnv(rs.Env)
	if err != nil {
		return DagStep{}, fmt.Errorf("env: %w", err)
	}

	// working_dir is an alias for dir at the step level.
	dir := rs.Dir
	if dir == "" {
		dir = rs.WorkingDir
	}

	return DagStep{
		Name:        rs.Name,
		ID:          rs.ID,
		Description: rs.Description,
		Command:     rs.Command,
		Script:      rs.Script,
		Args:        rs.Args,
		Shell:       rs.Shell,
		Dir:         dir,
		Depends:     rs.Depends,
		Env:         stepEnv,
		ContinueOn: DagContinueOn{
			Failure: rs.ContinueOn.Failure,
			Skipped: rs.ContinueOn.Skipped,
		},
		RetryPolicy: DagRetryPolicy{
			Limit:       rs.RetryPolicy.Limit,
			IntervalSec: rs.RetryPolicy.IntervalSec,
		},
		TimeoutSec: rs.TimeoutSec,
		Output:     rs.Output,
		Tags:       rs.Tags,
	}, nil
}

// normalizeHandlers converts rawDagHandlers to DagHandlers.
// Each handler field can be a single step object or a list of steps.
func normalizeHandlers(rh *rawDagHandlers) (DagHandlers, error) {
	var h DagHandlers
	var err error
	h.Init, err = normalizeHandlerField(rh.Init)
	if err != nil {
		return DagHandlers{}, fmt.Errorf("init: %w", err)
	}
	h.Success, err = normalizeHandlerField(rh.Success)
	if err != nil {
		return DagHandlers{}, fmt.Errorf("success: %w", err)
	}
	h.Failure, err = normalizeHandlerField(rh.Failure)
	if err != nil {
		return DagHandlers{}, fmt.Errorf("failure: %w", err)
	}
	h.Exit, err = normalizeHandlerField(rh.Exit)
	if err != nil {
		return DagHandlers{}, fmt.Errorf("exit: %w", err)
	}
	return h, nil
}

// normalizeHandlerField converts a handler field (single step or list) to []DagStep.
func normalizeHandlerField(v interface{}) ([]DagStep, error) {
	if v == nil {
		return nil, nil
	}

	// Re-marshal and unmarshal to handle polymorphic types cleanly.
	b, err := yaml.Marshal(v)
	if err != nil {
		return nil, fmt.Errorf("re-marshal handler: %w", err)
	}

	// Try as a list first.
	var rawList []rawDagStep
	if err := yaml.Unmarshal(b, &rawList); err == nil && len(rawList) > 0 {
		steps := make([]DagStep, 0, len(rawList))
		for i, rs := range rawList {
			step, err := normalizeStep(rs)
			if err != nil {
				return nil, fmt.Errorf("step[%d]: %w", i, err)
			}
			steps = append(steps, step)
		}
		return steps, nil
	}

	// Try as single step.
	var rs rawDagStep
	if err := yaml.Unmarshal(b, &rs); err != nil {
		return nil, fmt.Errorf("unmarshal handler step: %w", err)
	}
	step, err := normalizeStep(rs)
	if err != nil {
		return nil, err
	}
	// If the step has no meaningful content, return nil.
	if step.Name == "" && step.ID == "" && step.Command == "" && step.Script == "" {
		return nil, nil
	}
	return []DagStep{step}, nil
}