package redmine

import (
	"context"
	"fmt"
	"net/url"
	"strconv"
)

// Version is a roadmap milestone ("target version") of a project.
type Version struct {
	ID      int    `json:"id"`
	Name    string `json:"name"`
	DueDate string `json:"due_date,omitempty"`
	Status  string `json:"status"` // open|locked|closed
	Sharing string `json:"sharing,omitempty"`
}

// VersionParams is the write shape for CreateVersion/UpdateVersion. On
// update, zero fields are omitted so only what you set travels.
type VersionParams struct {
	Name    string
	DueDate string
	Status  string // "" defaults to open on create; omitted on update
	Sharing string // "" omits; "descendants" mirrors the PMO roadmap scripts
}

// ListVersions lists the versions of a project (by identifier or id).
func (c *Client) ListVersions(ctx context.Context, project string) ([]Version, error) {
	var body struct {
		Versions []Version `json:"versions"`
	}
	if err := c.do(ctx, "GET", "/projects/"+esc(project)+"/versions.json", nil, nil, &body); err != nil {
		return nil, err
	}
	return body.Versions, nil
}

// CreateVersion creates a roadmap milestone in a project.
func (c *Client) CreateVersion(ctx context.Context, project string, p VersionParams) (*Version, error) {
	if p.Name == "" {
		return nil, fmt.Errorf("%w: version name required", ErrValidation)
	}
	payload := map[string]any{"version": map[string]any{
		"name":      p.Name,
		"due_date":  optStr(p.DueDate),
		"status":    optStr(p.Status),
		"sharing":   optStr(p.Sharing),
	}}
	var body struct {
		Version Version `json:"version"`
	}
	if err := c.do(ctx, "POST", "/projects/"+esc(project)+"/versions.json", nil, payload, &body); err != nil {
		return nil, err
	}
	return &body.Version, nil
}

// UpdateVersion partially updates a version (PUT /versions/N.json).
// The server answers 204 with an EMPTY body — it is never parsed. Only
// the fields set in p are sent; untouched attributes are not clobbered.
func (c *Client) UpdateVersion(ctx context.Context, id int, p VersionParams) error {
	fields := map[string]any{}
	if p.Name != "" {
		fields["name"] = p.Name
	}
	if p.DueDate != "" {
		fields["due_date"] = p.DueDate
	}
	if p.Status != "" {
		fields["status"] = p.Status
	}
	if p.Sharing != "" {
		fields["sharing"] = p.Sharing
	}
	if len(fields) == 0 {
		return fmt.Errorf("%w: nothing to update", ErrValidation)
	}
	payload := map[string]any{"version": fields}
	return c.do(ctx, "PUT", "/versions/"+strconv.Itoa(id)+".json", nil, payload, nil)
}

// GetVersion fetches one version by id.
func (c *Client) GetVersion(ctx context.Context, id int) (*Version, error) {
	var body struct {
		Version Version `json:"version"`
	}
	if err := c.do(ctx, "GET", "/versions/"+strconv.Itoa(id)+".json", nil, nil, &body); err != nil {
		return nil, err
	}
	return &body.Version, nil
}

// Category is an issue category within a project.
type Category struct {
	ID   int    `json:"id"`
	Name string `json:"name"`
}

// ListCategories lists the issue categories of a project.
func (c *Client) ListCategories(ctx context.Context, project string) ([]Category, error) {
	var body struct {
		Categories []Category `json:"issue_categories"`
	}
	if err := c.do(ctx, "GET", "/projects/"+esc(project)+"/issue_categories.json", nil, nil, &body); err != nil {
		return nil, err
	}
	return body.Categories, nil
}

// CreateCategory creates an issue category in a project.
func (c *Client) CreateCategory(ctx context.Context, project, name string) (*Category, error) {
	if name == "" {
		return nil, fmt.Errorf("%w: category name required", ErrValidation)
	}
	payload := map[string]any{"issue_category": map[string]any{"name": name}}
	var body struct {
		Category Category `json:"issue_category"`
	}
	if err := c.do(ctx, "POST", "/projects/"+esc(project)+"/issue_categories.json", nil, payload, &body); err != nil {
		return nil, err
	}
	return &body.Category, nil
}

// Relation ties two issues together.
type Relation struct {
	ID           int    `json:"id"`
	IssueID      int    `json:"issue_id"`
	IssueToID    int    `json:"issue_to_id"`
	RelationType string `json:"relation_type"`
	Delay        int    `json:"delay,omitempty"`
}

// ValidRelationType reports whether t is a Redmine relation type.
func ValidRelationType(t string) bool {
	switch t {
	case "relates", "duplicates", "duplicated", "blocks", "blocked", "precedes", "follows", "copied_to", "copied_from":
		return true
	}
	return false
}

// CreateRelation creates issue_from -> issue_to of the given type
// ("blocks", "relates", ...).
func (c *Client) CreateRelation(ctx context.Context, from, to int, relationType string) (*Relation, error) {
	if !ValidRelationType(relationType) {
		return nil, fmt.Errorf("%w: relation type %q not allowed", ErrValidation, relationType)
	}
	payload := map[string]any{"relation": map[string]any{
		"issue_to_id":   to,
		"relation_type": relationType,
	}}
	var body struct {
		Relation Relation `json:"relation"`
	}
	path := "/issues/" + strconv.Itoa(from) + "/relations.json"
	if err := c.do(ctx, "POST", path, nil, payload, &body); err != nil {
		return nil, err
	}
	return &body.Relation, nil
}

// esc path-escapes a project identifier or id string.
func esc(s string) string { return url.PathEscape(s) }

// optStr maps "" to nil for omittable JSON string fields.
func optStr(s string) any {
	if s == "" {
		return nil
	}
	return s
}