#ifndef SQLCOMPLETIONPROVIDER_H
#define SQLCOMPLETIONPROVIDER_H

#include "SqlContext.h"
#include <QString>
#include <memory>
#include <vector>

class PgDatabaseCatalog;

struct CompletionItem {
	QString display;     // text shown in the list
	QString detail;      // dimmed extra information, for example the relation a column belongs to
	QString insertText;  // replaces the typed prefix when accepted
	CompletionKind kind = CompletionKind::None;
	bool ambiguous = false; // name occurs in more than one relation in scope
};

/// Plain snapshot of the parts of the catalog needed for completion, so the provider does not need a database.
struct CompletionRelation {
	QString schema;
	QString name;
	char kind = 'r'; // pg_class.relkind
	std::vector<QString> columns; // in column order, without dropped and system columns
};

struct CompletionFunction {
	QString schema;
	QString name;
	char kind = 'f'; // pg_proc.prokind: f function, a aggregate, w window
};

struct CompletionForeignKey {
	QString childSchema, childTable;   // table that has the constraint
	QString parentSchema, parentTable; // referenced table
	std::vector<QString> childColumns;
	std::vector<QString> parentColumns; // same length as childColumns
};

struct CompletionCatalog {
	std::vector<QString> schemas;
	std::vector<CompletionRelation> relations;
	std::vector<CompletionFunction> functions;
	std::vector<CompletionForeignKey> foreignKeys;
	/// Schemas that are searched when a relation is not schema qualified, in order
	std::vector<QString> searchPath = { QStringLiteral("public"), QStringLiteral("pg_catalog") };
};

CompletionCatalog buildCompletionCatalog(const PgDatabaseCatalog &catalog);

class SqlCompletionProvider {
public:
	SqlCompletionProvider() = default;
	explicit SqlCompletionProvider(CompletionCatalog catalog);

	std::vector<CompletionItem> complete(const SqlContext &ctx) const;

private:
	CompletionCatalog m_catalog;

	const CompletionRelation* resolve(const RelationRef &ref) const;
	std::vector<CompletionItem> relationItems(const SqlContext &ctx, const QString &schema) const;
	std::vector<CompletionItem> columnItems(const SqlContext &ctx) const;
	std::vector<CompletionItem> qualifiedColumnItems(const SqlContext &ctx) const;
	std::vector<CompletionItem> joinItems(const SqlContext &ctx) const;
	void addFunctionItems(const SqlContext &ctx, std::vector<CompletionItem> &items) const;
};

#endif // SQLCOMPLETIONPROVIDER_H