package fejkdata

import (
	"fmt"

	"github.com/larvit/fejkdata/internal/grammar"
)

// templateSite is a template to resolve, with its folder and category, both empty for an inline
// template, and eachNode's label for it.
type templateSite struct {
	t               *template
	folder          []string
	category, label string
}

// resolveCategoryTemplates resolves every template of the categories, once all data is merged, so a
// reference sees the override-resolved tree.
func resolveCategoryTemplates(sites []categorySite, root map[string]node) error {
	var ts []templateSite
	for _, s := range sites {
		if err := eachNode(s.n, s.path, func(label string, n node) error {
			if t, isTemplate := n.(*template); isTemplate {
				ts = append(ts, templateSite{t: t, folder: s.dir, category: s.path, label: label})
			}
			return nil
		}); err != nil {
			return err
		}
	}
	return resolveTemplates(ts, root)
}

func resolveInlineTemplates(nodes nodeSet, root map[string]node) error {
	var ts []templateSite
	if err := nodes(func(label string, n node) error {
		if t, isTemplate := n.(*template); isTemplate {
			ts = append(ts, templateSite{t: t, label: label})
		}
		return nil
	}); err != nil {
		return err
	}
	return resolveTemplates(ts, root)
}

// resolvedNames is what resolveTemplates resolved about the names of a set of templates: each binding's
// target, and the keys its reads address.
type resolvedNames struct {
	targets   map[*nameBinding]nameTarget
	addressed map[*nameBinding]map[pickKey]string
}

// resolveTemplates resolves ts in steps, each over every template before the next starts. The
// names' targets, keys and reads pass to later steps as arguments, and the bindings take their
// targets and keys only once every check has passed.
func resolveTemplates(ts []templateSite, root map[string]node) error {
	for _, s := range ts {
		refs, err := s.t.resolveRefs(s.folder, s.label, s.category, root)
		if err != nil {
			return err
		}
		s.t.refs = refs
	}
	targets := nameTargets(ts)
	for _, s := range ts {
		compiled, err := compileFormat(s.t, targets)
		if err != nil {
			return fmt.Errorf("%s: %w", s.label, err)
		}
		s.t.compiled = compiled
	}
	names := resolvedNames{targets: targets, addressed: addressedKeys(ts, targets)}
	for _, s := range ts {
		s.t.readsColumn = columnReadOf(s.t, targets)
	}
	for _, s := range ts {
		if err := checkNameReads(s.label, s.t, names); err != nil {
			return err
		}
	}
	for _, s := range ts {
		if err := checkCalcNames(s.label, s.t); err != nil {
			return err
		}
	}
	for b, target := range targets {
		b.target, b.addressed = target, names.addressed[b]
	}
	return nil
}

// columnRead is a record's column read by a format that only reads one reference or name,
// which is the column: it takes the column's datatype and null. category and field name it;
// category is "" for a column of the reading template's own record, which checkColumns reaches
// on its own.
type columnRead struct {
	a               arm
	category, field string
	column          node
}

// columnReadOf is the record's column t's format reads, where the format only reads one reference
// or name, and nil where it does not or t declares a string, which reads the column as text.
func columnReadOf(t *template, targets map[*nameBinding]nameTarget) *columnRead {
	ops := t.compiled.ops
	if t.datatype != nil && *t.datatype == DataTypeString || t.repeat != 1 || len(ops) != 1 || ops[0].Kind != grammar.PathRead || len(ops[0].arms) != 1 {
		return nil
	}
	a := ops[0].arms[0]
	var start node
	var category string
	var tail []string
	switch b := a.named; {
	case a.kind == namedRead && b.bindsField():
		// {f as n}{n}: column f of the record binding n, in t's own category.
		start, tail = b.binder, append(append([]string{splitArm(b.ref, nil).head}, targets[b].tail...), a.tail...)
	case a.kind == namedRead:
		// {/c as n}{n.x} or {/c.x as n}{n}: column x of category c.
		start, category = targets[b].start, categoryOf(b.binder.refs.byName[b.ref].head)
		tail = append(targets[b].tail[:len(targets[b].tail):len(targets[b].tail)], a.tail...)
	case grammar.IsRef(a.head):
		// {/c.x}: column x of category c.
		start, category, tail = t.startOf(a.head), categoryOf(a.head), a.tail
	default:
		return nil
	}
	if target, isTemplate := start.(*template); isTemplate && target.isRecord && len(tail) == 1 {
		return &columnRead{a: a, category: category, field: tail[0], column: target.fields[tail[0]]}
	}
	return nil
}