local postgres = {}

local Connection = {}
Connection.__index = Connection

function Connection:close()
	if self._id then
		local ok = moonshark.sql_close(self._id)
		self._id = nil
		return ok
	end
	return false
end

function Connection:ping()
	if not self._id then
		error("Connection is closed")
	end
	return moonshark.sql_ping(self._id)
end

function Connection:query(query_str, ...)
	if not self._id then
		error("Connection is closed")
	end
	return moonshark.sql_query(self._id, query_str:normalize_whitespace(), ...)
end

function Connection:exec(query_str, ...)
	if not self._id then
		error("Connection is closed")
	end
	return moonshark.sql_exec(self._id, query_str:normalize_whitespace(), ...)
end

function Connection:query_row(query_str, ...)
	local results = self:query(query_str, ...)
	return results and #results > 0 and results[1] or nil
end

function Connection:query_value(query_str, ...)
	local row = self:query_row(query_str, ...)
	if row then
		for _, value in pairs(row) do
			return value
		end
	end
	return nil
end

function Connection:begin()
	local result = self:exec("BEGIN")
	if result then
		return {
			conn = self,
			active = true,
			commit = function(tx)
				if tx.active then
					tx.active = false
					return tx.conn:exec("COMMIT")
				end
				return false
			end,
			rollback = function(tx)
				if tx.active then
					tx.active = false
					return tx.conn:exec("ROLLBACK")
				end
				return false
			end,
			savepoint = function(tx, name)
				if not tx.active then error("Transaction is not active") end
				if name:is_blank() then error("Savepoint name cannot be empty") end
				return tx.conn:exec("SAVEPOINT {{name}}":parse({name = name}))
			end,
			rollback_to = function(tx, name)
				if not tx.active then error("Transaction is not active") end
				if name:is_blank() then error("Savepoint name cannot be empty") end
				return tx.conn:exec("ROLLBACK TO SAVEPOINT {{name}}":parse({name = name}))
			end,
			query = function(tx, query_str, ...)
				if not tx.active then error("Transaction is not active") end
				return tx.conn:query(query_str, ...)
			end,
			exec = function(tx, query_str, ...)
				if not tx.active then error("Transaction is not active") end
				return tx.conn:exec(query_str, ...)
			end,
			query_row = function(tx, query_str, ...)
				if not tx.active then error("Transaction is not active") end
				return tx.conn:query_row(query_str, ...)
			end,
			query_value = function(tx, query_str, ...)
				if not tx.active then error("Transaction is not active") end
				return tx.conn:query_value(query_str, ...)
			end
		}
	end
	return nil
end

-- Build PostgreSQL parameters ($1, $2, etc.)
local function build_postgres_params(data)
	local keys = table.keys(data)
	local values = table.values(data)
	local placeholders = {}

	for i = 1, #keys do
		placeholders[i] = "$" .. i
	end

	return keys, values, placeholders
end

function Connection:insert(table_name, data, returning)
	if table_name:is_blank() then
		error("Table name cannot be empty")
	end

	local keys, values, placeholders = build_postgres_params(data)

	local query = "INSERT INTO {{table}} ({{columns}}) VALUES ({{placeholders}})":parse({
		table = table_name,
		columns = keys:join(", "),
		placeholders = table.concat(placeholders, ", ")
	})

	if returning and not returning:is_blank() then
		query = query .. " RETURNING " .. returning
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:upsert(table_name, data, conflict_columns, returning)
	if table_name:is_blank() then
		error("Table name cannot be empty")
	end

	local keys, values, placeholders = build_postgres_params(data)
	local updates = table.map(keys, function(key) return key .. " = EXCLUDED." .. key end)

	local conflict_clause = ""
	if conflict_columns then
		if type(conflict_columns) == "string" then
			conflict_clause = "(" .. conflict_columns .. ")"
		else
			conflict_clause = "(" .. table.concat(conflict_columns, ", ") .. ")"
		end
	end

	local query = "INSERT INTO {{table}} ({{columns}}) VALUES ({{placeholders}}) ON CONFLICT {{conflict}} DO UPDATE SET {{updates}}":parse({
		table = table_name,
		columns = keys:join(", "),
		placeholders = table.concat(placeholders, ", "),
		conflict = conflict_clause,
		updates = updates:join(", ")
	})

	if returning and not returning:is_blank() then
		query = query .. " RETURNING " .. returning
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:update(table_name, data, where_clause, returning, ...)
	if table_name:is_blank() then
		error("Table name cannot be empty")
	end
	if where_clause:is_blank() then
		error("WHERE clause cannot be empty for UPDATE")
	end

	local keys = table.keys(data)
	local values = table.values(data)
	local param_count = #keys

	-- Build SET clause with numbered parameters
	local sets = {}
	for i, key in ipairs(keys) do
		sets[i] = key .. " = $" .. i
	end

	-- Handle WHERE parameters
	local where_args = {...}
	local where_clause_final = where_clause
	for i = 1, #where_args do
		param_count = param_count + 1
		values[#values + 1] = where_args[i]
		where_clause_final = where_clause_final:replace("?", "$" .. param_count, 1)
	end

	local query = "UPDATE {{table}} SET {{sets}} WHERE {{where}}":parse({
		table = table_name,
		sets = table.concat(sets, ", "),
		where = where_clause_final
	})

	if returning and not returning:is_blank() then
		query = query .. " RETURNING " .. returning
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:delete(table_name, where_clause, returning, ...)
	if table_name:is_blank() then
		error("Table name cannot be empty")
	end
	if where_clause:is_blank() then
		error("WHERE clause cannot be empty for DELETE")
	end

	local where_args = {...}
	local values = {}
	local where_clause_final = where_clause

	for i = 1, #where_args do
		values[i] = where_args[i]
		where_clause_final = where_clause_final:replace("?", "$" .. i, 1)
	end

	local query = "DELETE FROM {{table}} WHERE {{where}}":parse({
		table = table_name,
		where = where_clause_final
	})

	if returning and not returning:is_blank() then
		query = query .. " RETURNING " .. returning
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:select(table_name, columns, where_clause, ...)
	if table_name:is_blank() then
		error("Table name cannot be empty")
	end

	columns = columns or "*"
	if type(columns) == "table" then
		columns = table.concat(columns, ", ")
	end

	if where_clause and not where_clause:is_blank() then
		local where_args = {...}
		local values = {}
		local where_clause_final = where_clause

		for i = 1, #where_args do
			values[i] = where_args[i]
			where_clause_final = where_clause_final:replace("?", "$" .. i, 1)
		end

		local query = "SELECT {{columns}} FROM {{table}} WHERE {{where}}":parse({
			columns = columns,
			table = table_name,
			where = where_clause_final
		})
		return self:query(query, unpack(values))
	else
		local query = "SELECT {{columns}} FROM {{table}}":parse({
			columns = columns,
			table = table_name
		})
		return self:query(query)
	end
end

-- Schema helpers
function Connection:table_exists(table_name, schema_name)
	if table_name:is_blank() then return false end
	schema_name = schema_name or "public"
	return self:query_value("SELECT tablename FROM pg_tables WHERE schemaname = $1 AND tablename = $2",
		schema_name:trim(), table_name:trim()) ~= nil
end

function Connection:column_exists(table_name, column_name, schema_name)
	if table_name:is_blank() or column_name:is_blank() then return false end
	schema_name = schema_name or "public"
	return self:query_value([[
		SELECT column_name FROM information_schema.columns
		WHERE table_schema = $1 AND table_name = $2 AND column_name = $3
	]], schema_name:trim(), table_name:trim(), column_name:trim()) ~= nil
end

function Connection:create_table(table_name, schema)
	if table_name:is_blank() or schema:is_blank() then
		error("Table name and schema cannot be empty")
	end
	return self:exec("CREATE TABLE IF NOT EXISTS {{table}} ({{schema}})":parse({
		table = table_name,
		schema = schema:trim()
	}))
end

function Connection:drop_table(table_name, cascade)
	if table_name:is_blank() then
		error("Table name cannot be empty")
	end
	local cascade_clause = cascade and " CASCADE" or ""
	return self:exec("DROP TABLE IF EXISTS {{table}}{{cascade}}":parse({
		table = table_name,
		cascade = cascade_clause
	}))
end

function Connection:add_column(table_name, column_def)
	if table_name:is_blank() or column_def:is_blank() then
		error("Table name and column definition cannot be empty")
	end
	return self:exec("ALTER TABLE {{table}} ADD COLUMN IF NOT EXISTS {{column}}":parse({
		table = table_name,
		column = column_def:trim()
	}))
end

function Connection:drop_column(table_name, column_name, cascade)
	if table_name:is_blank() or column_name:is_blank() then
		error("Table name and column name cannot be empty")
	end
	local cascade_clause = cascade and " CASCADE" or ""
	return self:exec("ALTER TABLE {{table}} DROP COLUMN IF EXISTS {{column}}{{cascade}}":parse({
		table = table_name,
		column = column_name,
		cascade = cascade_clause
	}))
end

function Connection:create_index(index_name, table_name, columns, unique, method)
	if index_name:is_blank() or table_name:is_blank() then
		error("Index name and table name cannot be empty")
	end

	local unique_clause = unique and "UNIQUE " or ""
	local method_clause = method and " USING " .. method:upper() or ""
	local columns_str = type(columns) == "table" and table.concat(columns, ", ") or tostring(columns)

	return self:exec("CREATE {{unique}}INDEX IF NOT EXISTS {{index}} ON {{table}}{{method}} ({{columns}})":parse({
		unique = unique_clause,
		index = index_name,
		table = table_name,
		method = method_clause,
		columns = columns_str
	}))
end

function Connection:drop_index(index_name, cascade)
	if index_name:is_blank() then
		error("Index name cannot be empty")
	end
	local cascade_clause = cascade and " CASCADE" or ""
	return self:exec("DROP INDEX IF EXISTS {{index}}{{cascade}}":parse({
		index = index_name,
		cascade = cascade_clause
	}))
end

-- PostgreSQL-specific functions
function Connection:vacuum(table_name, analyze)
	local analyze_clause = analyze and " ANALYZE" or ""
	local table_clause = table_name and " " .. table_name or ""
	return self:exec("VACUUM{{analyze}}{{table}}":parse({
		analyze = analyze_clause,
		table = table_clause
	}))
end

function Connection:analyze(table_name)
	local table_clause = table_name and " " .. table_name or ""
	return self:exec("ANALYZE{{table}}":parse({table = table_clause}))
end

function Connection:reindex(name, type)
	if name:is_blank() then
		error("Name cannot be empty for REINDEX")
	end

	type = (type or "INDEX"):upper()
	local valid_types = {"INDEX", "TABLE", "SCHEMA", "DATABASE", "SYSTEM"}

	if not table.contains(valid_types, type) then
		error("Invalid REINDEX type: " .. type)
	end

	return self:exec("REINDEX {{type}} {{name}}":parse({type = type, name = name}))
end

function Connection:show(setting)
	if setting:is_blank() then
		error("Setting name cannot be empty")
	end
	return self:query_value("SHOW {{setting}}":parse({setting = setting}))
end

function Connection:set(setting, value)
	if setting:is_blank() then
		error("Setting name cannot be empty")
	end
	return self:exec("SET {{setting}} = {{value}}":parse({
		setting = setting,
		value = tostring(value)
	}))
end

function Connection:current_database()
	return self:query_value("SELECT current_database()")
end

function Connection:current_schema()
	return self:query_value("SELECT current_schema()")
end

function Connection:version()
	return self:query_value("SELECT version()")
end

function Connection:list_schemas()
	return self:query("SELECT schema_name FROM information_schema.schemata ORDER BY schema_name")
end

function Connection:list_tables(schema_name)
	schema_name = schema_name or "public"
	return self:query("SELECT tablename FROM pg_tables WHERE schemaname = $1 ORDER BY tablename", schema_name:trim())
end

function Connection:describe_table(table_name, schema_name)
	if table_name:is_blank() then
		error("Table name cannot be empty")
	end

	schema_name = schema_name or "public"
	return self:query([[
		SELECT column_name, data_type, is_nullable, column_default
		FROM information_schema.columns
		WHERE table_schema = $1 AND table_name = $2
		ORDER BY ordinal_position
	]], schema_name:trim(), table_name:trim())
end

-- JSON/JSONB helpers
function Connection:json_extract(column, path)
	if column:is_blank() or path:is_blank() then
		error("Column and path cannot be empty")
	end
	return "{{column}}->'{{path}}'":parse({column = column, path = path})
end

function Connection:json_extract_text(column, path)
	if column:is_blank() or path:is_blank() then
		error("Column and path cannot be empty")
	end
	return "{{column}}->>'{{path}}'":parse({column = column, path = path})
end

function Connection:jsonb_contains(column, value)
	if column:is_blank() or value:is_blank() then
		error("Column and value cannot be empty")
	end
	return "{{column}} @> '{{value}}'":parse({column = column, value = value})
end

function Connection:jsonb_contained_by(column, value)
	if column:is_blank() or value:is_blank() then
		error("Column and value cannot be empty")
	end
	return "{{column}} <@ '{{value}}'":parse({column = column, value = value})
end

-- Array helpers
function Connection:array_contains(column, value)
	if column:is_blank() then
		error("Column cannot be empty")
	end
	return "$1 = ANY({{column}})":parse({column = column})
end

function Connection:array_length(column)
	if column:is_blank() then
		error("Column cannot be empty")
	end
	return "array_length({{column}}, 1)":parse({column = column})
end

-- Connection management
function postgres.parse_dsn(dsn)
	if dsn:is_blank() then
		return nil, "DSN cannot be empty"
	end

	local parts = {}
	for pair in dsn:trim():gmatch("[^%s]+") do
		local key, value = pair:match("([^=]+)=(.+)")
		if key and value then
			parts[key:trim()] = value:trim()
		end
	end

	return parts
end

function postgres.connect(dsn)
	if dsn:is_blank() then
		error("DSN cannot be empty")
	end

	local conn_id = moonshark.sql_connect("postgres", dsn:trim())
	if conn_id then
		return setmetatable({_id = conn_id}, Connection)
	end
	return nil
end

postgres.open = postgres.connect

-- Quick execution functions
function postgres.query(dsn, query_str, ...)
	local conn = postgres.connect(dsn)
	if not conn then
		error("Failed to connect to PostgreSQL database")
	end

	local results = conn:query(query_str, ...)
	conn:close()
	return results
end

function postgres.exec(dsn, query_str, ...)
	local conn = postgres.connect(dsn)
	if not conn then
		error("Failed to connect to PostgreSQL database")
	end

	local result = conn:exec(query_str, ...)
	conn:close()
	return result
end

function postgres.query_row(dsn, query_str, ...)
	local results = postgres.query(dsn, query_str, ...)
	return results and #results > 0 and results[1] or nil
end

function postgres.query_value(dsn, query_str, ...)
	local row = postgres.query_row(dsn, query_str, ...)
	if row then
		for _, value in pairs(row) do
			return value
		end
	end
	return nil
end

-- Migration helpers
function postgres.migrate(dsn, migrations, schema)
	schema = schema or "public"
	local conn = postgres.connect(dsn)
	if not conn then
		error("Failed to connect to PostgreSQL database for migration")
	end

	conn:create_table("_migrations", "id SERIAL PRIMARY KEY, name TEXT UNIQUE NOT NULL, applied_at TIMESTAMPTZ DEFAULT NOW()")

	local tx = conn:begin()
	if not tx then
		conn:close()
		error("Failed to begin migration transaction")
	end

	for _, migration in ipairs(migrations) do
		if not migration.name or migration.name:is_blank() then
			tx:rollback()
			conn:close()
			error("Migration must have a non-empty name")
		end

		local existing = conn:query_value("SELECT id FROM _migrations WHERE name = $1", migration.name:trim())
		if not existing then
			local ok, err = pcall(function()
				if type(migration.up) == "string" then
					conn:exec(migration.up)
				elseif type(migration.up) == "function" then
					migration.up(conn)
				else
					error("Migration 'up' must be string or function")
				end
			end)

			if ok then
				conn:exec("INSERT INTO _migrations (name) VALUES ($1)", migration.name:trim())
				print("Applied migration: {{name}}":parse({name = migration.name}))
			else
				tx:rollback()
				conn:close()
				error("Migration '{{name}}' failed: {{error}}":parse({
					name = migration.name,
					error = err or "unknown error"
				}))
			end
		end
	end

	tx:commit()
	conn:close()
	return true
end

-- Result processing utilities
function postgres.to_array(results, column_name)
	if not results or table.is_empty(results) then return {} end
	if column_name:is_blank() then error("Column name cannot be empty") end
	return table.map(results, function(row) return row[column_name] end)
end

function postgres.to_map(results, key_column, value_column)
	if not results or table.is_empty(results) then return {} end
	if key_column:is_blank() then error("Key column name cannot be empty") end

	local map = {}
	for _, row in ipairs(results) do
		local key = row[key_column]
		map[key] = value_column and row[value_column] or row
	end
	return map
end

function postgres.group_by(results, column_name)
	if not results or table.is_empty(results) then return {} end
	if column_name:is_blank() then error("Column name cannot be empty") end
	return table.group_by(results, function(row) return row[column_name] end)
end

function postgres.print_results(results)
	if not results or table.is_empty(results) then
		print("No results")
		return
	end

	local columns = table.keys(results[1])
	table.sort(columns)

	-- Calculate column widths
	local widths = {}
	for _, col in ipairs(columns) do
		widths[col] = col:length()
		for _, row in ipairs(results) do
			local value = tostring(row[col] or "")
			widths[col] = math.max(widths[col], value:length())
		end
	end

	-- Print header and separator
	local header_parts = table.map(columns, function(col) return col:pad_right(widths[col]) end)
	local separator_parts = table.map(columns, function(col) return string.repeat_("-", widths[col]) end)

	print(table.concat(header_parts, " | "))
	print(table.concat(separator_parts, "-+-"))

	-- Print rows
	for _, row in ipairs(results) do
		local value_parts = table.map(columns, function(col)
			local value = tostring(row[col] or "")
			return value:pad_right(widths[col])
		end)
		print(table.concat(value_parts, " | "))
	end
end

function postgres.escape_identifier(name)
	if name:is_blank() then
		error("Identifier name cannot be empty")
	end
	return '"{{name}}"':parse({name = name:replace('"', '""')})
end

function postgres.escape_literal(value)
	if type(value) == "string" then
		return "'{{value}}'":parse({value = value:replace("'", "''")})
	end
	return tostring(value)
end

return postgres